0001524741-24-000015 | 10-Q | XBRL Viewer

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CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock authorized (in shares)	10,000,000	10,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (in shares)	500,000,000	500,000,000
Common stock issued (in shares)	89,403,532	87,970,110
Common stock outstanding (in shares)	78,090,519	77,192,239
Treasury stock, at cost (in shares)	11,313,013	10,777,871

Inventories

3 Months Ended

Mar. 31, 2024

Inventory Disclosure [Abstract]

INVENTORIES

NOTE F—INVENTORIES

Inventories (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Supplies	$	65,086	$	65,422
Raw materials and work in process	53,315		54,142
Finished goods	21,134		29,865
Total inventories	$	139,535	$	149,429

Property, Plant and Mine Development - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment
Depreciation, depletion and amortization	$ 31,368	$ 35,386
Property, Plant and Equipment
Property, Plant and Equipment
Depreciation, depletion and amortization	$ 28,100	$ 32,300

Fair Value Accounting	3 Months Ended
Fair Value Accounting	Mar. 31, 2024
Fair Value Disclosures [Abstract]
FAIR VALUE ACCOUNTING	NOTE K—FAIR VALUE ACCOUNTING Fair value is defined as the price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Cash Equivalents Due to the short-term maturity, we believe our cash equivalent instruments approximated their reported carrying values, therefore we have classified our cash equivalents as Level 1 of the fair value hierarchy. Long-Term Debt, Including Current Maturities The fair values of our long-term debt, including current maturities, approximated their carrying values based on their effective interest rates compared to current market rates, therefore we have classified our long-term debt as Level 1 of the fair value hierarchy. Derivative Instruments The estimated fair value of our derivative instruments is recorded at each reporting period and is determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets. Therefore, we have classified these swap agreements as Level 2 of the fair value hierarchy.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Debt - (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Line of Credit Facility
Less: Unamortized original issue discount	$ (24,598)	$ (24,183)
Less: Unamortized debt issuance cost	(12,733)	(13,421)
Finance leases (See Note P - Leases)	2,684	3,108
Total debt	809,463	840,037
Less: current portion	(12,708)	(16,367)
Total long-term portion of debt	796,755	823,670
Notes Payable \| Insurance financing notes payable
Line of Credit Facility
Insurance financing notes payable	$ 3,235	$ 6,470
Revolving Line-of-Credit \| Revolver expiring March 23, 2028 (10.18% at March 31, 2024 and 10.21% at December 31, 2023)
Line of Credit Facility
Interest rate	10.18%	10.21%
Long-term debt	$ 0	$ 0
Senior Secured Credit Facility \| Term Loan—final maturity March 23, 2030 (9.33% at March 31, 2024 and 10.21% at December 31, 2023)
Line of Credit Facility
Interest rate	9.33%	10.21%
Long-term debt	$ 840,875	$ 868,063

Accounts Receivable - Narrative (Details)	3 Months Ended
Accounts Receivable - Narrative (Details)	Mar. 31, 2024	Mar. 31, 2023
Customer Concentration Risk \| Sales \| Ten Largest Customers
Concentration Risk [Line Items]
Concentration risk percentage (as a percent)	47.00%	45.00%

Goodwill and Intangible Assets - Carrying Amount of Goodwill by Business Segment (Details)	3 Months Ended
	Mar. 31, 2024 USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2023	$ 185,649,000
Impairment loss	0
Balance at March 31, 2024	185,649,000
Oil & Gas Proppants Segment
Goodwill [Roll Forward]
Balance at December 31, 2023	0
Impairment loss	0
Balance at March 31, 2024	0
Industrial & Specialty Products Segment
Goodwill [Roll Forward]
Balance at December 31, 2023	185,649,000
Impairment loss	0
Balance at March 31, 2024	$ 185,649,000

Debt - Contractual Maturities of Term Loan (Details) - Senior Secured Credit Facility - Term Loan - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
2024 (remaining nine months)	$ 6,375
2025	8,500
2026	8,500
2027	8,500
2028	8,500
Thereafter	800,500
Total	$ 840,875	$ 868,063

Segment Reporting

3 Months Ended

Mar. 31, 2024

Segment Reporting [Abstract]

SEGMENT REPORTING

NOTE T— SEGMENT REPORTING

Our business is organized into two reportable segments, Oil & Gas Proppants and Industrial & Specialty Products, based on end markets. The reportable segments are consistent with how management views the markets that we serve and the financial information reviewed by the chief operating decision maker. We manage our Oil & Gas Proppants and Industrial & Specialty Products businesses as components of an enterprise for which separate information is available and is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and assess performance.

In the Oil & Gas Proppants segment, we serve the oil and gas recovery market primarily by providing and delivering fracturing sand, or “frac sand,” which is pumped down oil and natural gas wells to prop open rock fissures and increase the flow rate of oil and natural gas from the wells.

The Industrial & Specialty Products segment consists of over 800 product types and materials used in a variety of industries, including container glass, fiberglass, specialty glass, flat glass, building products, fillers and extenders, foundry products, chemicals, recreation products and filtration products.

An operating segment’s performance is primarily evaluated based on segment contribution margin, which excludes selling, general, and administrative costs, depreciation, depletion and amortization, corporate costs, plant capacity expansion expenses, and facility closure costs. We believe that segment contribution margin, as defined above, is an appropriate measure for evaluating the operating performance of our segments. However, segment contribution margin is a non-GAAP measure and should be considered in addition to, not a substitute for, or superior to, net income (loss) or other measures of financial performance prepared in accordance with GAAP. The other accounting policies of each of the two reportable segments are the same as those in Note B - Summary of Significant Accounting Policies to the Consolidated Financial Statements in Item 8 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2023.

The following table presents sales and segment contribution margin (in thousands) for the reportable segments and other operating results not allocated to the reportable segments:


	Three Months Ended March 31,
	2024		2023
Sales:
Oil & Gas Proppants	$	183,172	$	300,013
Industrial & Specialty Products	142,770		142,227
Total sales	325,942		442,240
Segment contribution margin:
Oil & Gas Proppants	59,515		109,897
Industrial & Specialty Products	45,949		42,929
Total segment contribution margin	105,464		152,826
Operating activities excluded from segment cost of sales	(3,246)		(3,719)
Selling, general and administrative	(30,754)		(29,163)
Depreciation, depletion and amortization	(31,368)		(35,386)

Interest expense	(24,263)		(24,061)
Other income (expense), net, including interest income	2,523		(2,352)
Income tax expense	(4,775)		(13,573)
Net income	$	13,581	$	44,572
Less: Net loss attributable to non-controlling interest	(107)		(76)
Net income attributable to U.S. Silica Holdings, Inc.	$	13,688	$	44,648

Asset information, including capital expenditures and depreciation, depletion, and amortization, by segment is not included in reports used by management in its monitoring of performance and, therefore, is not reported by segment. At both March 31, 2024 and December 31, 2023, goodwill of $185.6 million has been allocated to these segments with zero allocated to Oil & Gas Proppants and $185.6 million to Industrial & Specialty Products.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-15

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//280/tableOfContent

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-26

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-34

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

+ Details

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment	$ 0
Amortization expense of intangibles	$ 2,400,000	$ 2,400,000
Technology and intellectual property
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangibles	15 years
Customer relationships \| Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangibles	13 years
Customer relationships \| Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful lives of intangibles	20 years

Accumulated Other Comprehensive Income (Loss) (Tables)

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Schedule of Changes in Accumulated Other Comprehensive Income (Loss)

The following table presents the changes in accumulated other comprehensive income (loss) by component (in thousands):


	For the Three Months Ended March 31, 2024
	Unrealized (loss) gain on natural gas swaps		Foreign currency translation adjustments		Pension and other post-retirement benefits liability		Total
Beginning Balance	$	(1,460)	$	(981)	$	2,316	$	(125)
Other comprehensive income (loss) before reclassifications	84		(144)		3,311		3,251
Amounts reclassified from accumulated other comprehensive income	—		—		(503)		(503)
Ending Balance	$	(1,376)	$	(1,125)	$	5,124	$	2,623

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited Condensed Consolidated Financial Statements as of and for the three months ended March 31, 2024 included in this Quarterly Report on Form 10-Q have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the U.S. Securities and Exchange Commission (“SEC”). They do not contain certain information included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2023; therefore, the unaudited Condensed Consolidated Financial Statements should be read in conjunction with that Annual Report on Form 10-K. Operating results for the three-month period ended March 31, 2024 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2024. In the opinion of management, all adjustments necessary for a fair presentation have been included. Such adjustments are of a normal, recurring nature.
Consolidation	The unaudited Condensed Consolidated Financial Statements include the accounts of Holdings and its direct and indirect wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates and Assumptions	Use of Estimates and Assumptions The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The areas requiring the use of management estimates and assumptions relate to the purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for credit losses; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill, intangible assets and other long-lived assets); write-downs of inventory to net realizable value; equity-based compensation expense; post-employment, post-retirement and other employee benefit liabilities; valuation allowances for deferred tax assets; contingent considerations; reserves for contingencies and litigation and the fair value and accounting treatment of financial instruments. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may differ significantly from these estimates under different assumptions or conditions.
New Accounting Pronouncements Recently Adopted and New Accounting Pronouncements Not Yet Adopted	New Accounting Pronouncements Recently Adopted None. New Accounting Pronouncements Not Yet Adopted In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The amendments in this Update improve financial reporting by requiring disclosure of incremental segment information on an annual and interim basis for all public entities to enable investors to develop more decision-useful financial analyses. The amendments in this Update do not change or remove current disclosure requirements as required by Topic 280. The amendments in this Update also do not change how a public entity identifies its operating segments, aggregates those operating segments, or applies the quantitative thresholds to determine its reportable segments. The amendments in this Update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Public entities will be required to apply the amendments in this Update retrospectively to all prior periods presented in the financial statements. We are currently evaluating the effect this guidance will have on our disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The amendments in this Update related to the rate reconciliation and income taxes paid disclosures improve the transparency of income tax disclosures by requiring (1) consistent categories and greater disaggregation of information in the rate reconciliation and (2) income taxes paid disaggregated by jurisdiction. The amendments allow investors to better assess, in their capital allocation decisions, how an entity’s worldwide operations and related tax risks and tax planning and operational opportunities affect its income tax rate and prospects for future cash flows. The other amendments in this Update improve the effectiveness and comparability of disclosures by (1) adding disclosures of pretax income (or loss) and income tax expense (or benefit) to be consistent with U.S. Securities and Exchange Commission (SEC) Regulation S-X 210.4-08(h), Rules of General Application—General Notes to Financial Statements: Income Tax Expense, and (2) removing disclosures that no longer are considered cost beneficial or relevant. The amendments in this Update are effective for annual periods beginning after December 15, 2024. We are currently evaluating the effect this guidance will have on our disclosures.
Fair Value Accounting	Fair value is defined as the price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. Cash Equivalents Due to the short-term maturity, we believe our cash equivalent instruments approximated their reported carrying values, therefore we have classified our cash equivalents as Level 1 of the fair value hierarchy. Long-Term Debt, Including Current Maturities The fair values of our long-term debt, including current maturities, approximated their carrying values based on their effective interest rates compared to current market rates, therefore we have classified our long-term debt as Level 1 of the fair value hierarchy. Derivative Instruments The estimated fair value of our derivative instruments is recorded at each reporting period and is determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets. Therefore, we have classified these swap agreements as Level 2 of the fair value hierarchy.

Asset Retirement Obligations (Tables)

3 Months Ended

Mar. 31, 2024

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Changes in Asset Retirement Obligations

Changes in the asset retirement obligations (in thousands) are as follows:


	Three Months Ended March 31,
	2024		2023
Beginning balance	$	30,414	$	20,732
Accretion	612		512
Additions and revisions of estimates	1,469		—
Payments	—		(14)
Ending balance	$	32,495	$	21,230

Asset Retirement Obligations

3 Months Ended

Mar. 31, 2024

Asset Retirement Obligation Disclosure [Abstract]

ASSET RETIREMENT OBLIGATIONS

NOTE J—ASSET RETIREMENT OBLIGATIONS

Mine reclamation or future remediation costs for inactive mines are accrued based on management’s best estimate at the end of each period of the costs expected to be incurred at such site at the expected abandonment date. Such cost estimates include, where applicable, ongoing care, maintenance and monitoring costs. Changes in estimates at inactive mines are reflected in earnings in the period an estimate is revised. Liabilities related to our asset retirement obligations are reflected in other long-term liabilities on our balance sheets. Changes in the asset retirement obligations (in thousands) are as follows:


	Three Months Ended March 31,
	2024		2023
Beginning balance	$	30,414	$	20,732
Accretion	612		512
Additions and revisions of estimates	1,469		—
Payments	—		(14)
Ending balance	$	32,495	$	21,230

Asset Retirement Obligations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 30,414	$ 20,732
Accretion	612	512
Additions and revisions of estimates	1,469	0
Payments	0	(14)
Ending balance	$ 32,495	$ 21,230

Pension and Post-Retirement Benefits - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) plan	Mar. 31, 2023 USD ($)
Pension Plans, Postretirement and Other Employee Benefits
Number of multiemployer defined benefit plans \| plan	3
Percentage of contributions to individual multiemployer plan (less than)	5.00%	5.00%
Company contributions to qualified pension plans	$ 2.8	$ 2.1
Certain Employees
Pension Plans, Postretirement and Other Employee Benefits
Percentage of contribution over defined benefit plan	4.00%
All Other Eligible Employees
Pension Plans, Postretirement and Other Employee Benefits
Percentage of contribution over defined benefit plan based on eligible earnings (up to)	6.00%
Pension Plans
Pension Plans, Postretirement and Other Employee Benefits
Expected contributions to the plans for the 2023 fiscal year	$ 4.8
Post-retirement Medical Plan
Pension Plans, Postretirement and Other Employee Benefits
Expected contributions to the plans for the 2023 fiscal year	$ 0.9

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Sales:
Total sales	$ 325,942	$ 442,240
Cost of sales (excluding depreciation, depletion and amortization):
Total cost of sales (excluding depreciation, depletion and amortization)	223,724	293,133
Operating expenses:
Selling, general and administrative	30,754	29,163
Depreciation, depletion and amortization	31,368	35,386
Total operating expenses	62,122	64,549
Operating income	40,096	84,558
Other (expense) income:
Interest expense	(24,263)	(24,061)
Other income (expense), net, including interest income	2,523	(2,352)
Total other expense	(21,740)	(26,413)
Income before income taxes	18,356	58,145
Income tax expense	(4,775)	(13,573)
Net income	13,581	44,572
Less: Net loss attributable to non-controlling interest	(107)	(76)
Net income attributable to U.S. Silica Holdings, Inc.	$ 13,688	$ 44,648
Earnings per share attributable to U.S. Silica Holdings, Inc.:
Basic (in dollars per share)	$ 0.18	$ 0.58
Diluted (in dollars per share)	$ 0.17	$ 0.57
Weighted average shares outstanding:
Basic (in shares)	77,671	76,517
Diluted (in shares)	79,032	78,292
Product
Sales:
Total sales	$ 261,794	$ 344,014
Cost of sales (excluding depreciation, depletion and amortization):
Total cost of sales (excluding depreciation, depletion and amortization)	178,714	225,894
Service
Sales:
Total sales	64,148	98,226
Cost of sales (excluding depreciation, depletion and amortization):
Total cost of sales (excluding depreciation, depletion and amortization)	$ 45,010	$ 67,239

Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2024

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value

The following table summarizes the fair values of our derivative instruments (in thousands, except contract/notional amount). See Note K - Fair Value Accounting for more information regarding the estimated fair values of our derivative instruments.


	March 31, 2024						December 31, 2023
	Maturity Date	Contract/Notional Amount (MMBtu)	Carrying Amount		Fair Value		Maturity Date	Contract/Notional Amount (MMBtu)	Carrying Amount		Fair Value

Natural Gas - W. Texas (WAHA) - Inside FERC	2024	870,000	$	(1,475)	$	(1,475)	2024	870,000	$	(1,542)	$	(1,542)
Natural Gas - W. Texas (WAHA) - Inside FERC	2024	750,000	$	—	$	—	2024	750,000	$	(11)	$	(11)

Natural Gas - Henry Hub - NYMEX	2024	120,000	$	(218)	$	(218)	2024	120,000	$	(258)	$	(258)
Natural Gas - Henry Hub - NYMEX	2025	90,000	$	(121)	$	(121)	2025	90,000	$	(115)	$	(115)

Schedule of Effect of Derivatives Instruments on Combined Statements of Operations and Comprehensive Income

The following table summarizes the effect of derivative instruments (in thousands) on our income statements and our consolidated statements of comprehensive income:


	Three Months Ended March 31,
	2024		2023
Deferred losses from derivatives in OCI, beginning of period	$	(1,460)	$	(2,342)
Gain (loss) recognized in OCI from derivative instruments	84		(969)
Deferred losses from derivatives in OCI, end of period	$	(1,376)	$	(3,311)

Accounts Receivable - Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Receivables [Abstract]
Trade receivables	$ 192,998	$ 190,189
Less: Allowance for credit losses	(4,324)	(5,323)
Net trade receivables	188,674	184,866
Other receivables	832	1,051
Total accounts receivable	$ 189,506	$ 185,917

Property, Plant and Mine Development

3 Months Ended

Mar. 31, 2024

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT AND MINE DEVELOPMENT

NOTE G—PROPERTY, PLANT AND MINE DEVELOPMENT

Property, plant and mine development (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Mining property and mine development	$	799,120	$	793,582
Asset retirement cost	16,550		14,728
Land	53,100		53,100
Land improvements	87,618		87,618
Buildings	77,294		76,691
Machinery and equipment	1,259,972		1,253,734
Furniture and fixtures	3,017		2,841
Construction-in-progress	48,992		54,186
	2,345,663		2,336,480
Accumulated depreciation, depletion, amortization and impairment charges	(1,238,311)		(1,211,260)
Total property, plant and mine development, net	$	1,107,352	$	1,125,220

Depreciation, depletion, and amortization expense related to property, plant and mine development was $28.1 million and $32.3 million for the three months ended March 31, 2024 and 2023, respectively.

Property, Plant and Mine Development (Tables)

3 Months Ended

Mar. 31, 2024

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Mine Development

Property, plant and mine development (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Mining property and mine development	$	799,120	$	793,582
Asset retirement cost	16,550		14,728
Land	53,100		53,100
Land improvements	87,618		87,618
Buildings	77,294		76,691
Machinery and equipment	1,259,972		1,253,734
Furniture and fixtures	3,017		2,841
Construction-in-progress	48,992		54,186
	2,345,663		2,336,480
Accumulated depreciation, depletion, amortization and impairment charges	(1,238,311)		(1,211,260)
Total property, plant and mine development, net	$	1,107,352	$	1,125,220

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Total U.S. Silica Holdings Inc., Stockholders’ Equity	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Deficit	Accumulated Other Comprehensive (Loss) Income	Non-controlling Interest
Beginning Balance at Dec. 31, 2022	$ 704,694	$ 696,685	$ 854	$ (186,196)	$ 1,234,834	$ (351,084)	$ (1,723)	$ 8,009
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	44,572	44,648				44,648		(76)
Unrealized gain on derivatives	(969)	(969)					(969)
Foreign currency translation adjustment	222	222					222
Pension and post-retirement liability	22	22					22
Distributions to non-controlling interest	(350)							(350)
Common stock-based compensation plans activity:
Equity-based compensation	3,286	3,286			3,286
Tax payments related to shares withheld for vested restricted stock and stock units	(9,920)	(9,920)	22	(9,920)	(22)
Ending Balance at Mar. 31, 2023	741,557	733,974	876	(196,116)	1,238,098	(306,436)	(2,448)	7,583
Beginning Balance at Dec. 31, 2023	855,527	849,308	877	(196,745)	1,249,460	(204,159)	(125)	6,219
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	13,581	13,688				13,688		(107)
Unrealized gain on derivatives	84	84					84
Foreign currency translation adjustment	(144)	(144)					(144)
Pension and post-retirement liability	2,808	2,808					2,808
Contributions from non-controlling interest	36							36
Common stock-based compensation plans activity:
Equity-based compensation	4,051	4,051			4,051
Tax payments related to shares withheld for vested restricted stock and stock units	(5,618)	(5,618)	14	(5,618)	(14)
Ending Balance at Mar. 31, 2024	$ 870,325	$ 864,177	$ 891	$ (202,363)	$ 1,253,497	$ (190,471)	$ 2,623	$ 6,148

Segment Reporting (Tables)

3 Months Ended

Mar. 31, 2024

Segment Reporting [Abstract]

Schedule of Sales and Segment Contribution Margin for Reporting Segments and Operating Results

The following table presents sales and segment contribution margin (in thousands) for the reportable segments and other operating results not allocated to the reportable segments:


	Three Months Ended March 31,
	2024		2023
Sales:
Oil & Gas Proppants	$	183,172	$	300,013
Industrial & Specialty Products	142,770		142,227
Total sales	325,942		442,240
Segment contribution margin:
Oil & Gas Proppants	59,515		109,897
Industrial & Specialty Products	45,949		42,929
Total segment contribution margin	105,464		152,826
Operating activities excluded from segment cost of sales	(3,246)		(3,719)
Selling, general and administrative	(30,754)		(29,163)
Depreciation, depletion and amortization	(31,368)		(35,386)

Interest expense	(24,263)		(24,061)
Other income (expense), net, including interest income	2,523		(2,352)
Income tax expense	(4,775)		(13,573)
Net income	$	13,581	$	44,572
Less: Net loss attributable to non-controlling interest	(107)		(76)
Net income attributable to U.S. Silica Holdings, Inc.	$	13,688	$	44,648

Commitments and Contingencies

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

NOTE N—COMMITMENTS AND CONTINGENCIES

Future Minimum Annual Commitments at March 31, 2024 (in thousands):


	Minimum Purchase Commitments
2024 (remaining nine months)	$	8,730
2025	6,661
2026	4,520
2027	2,048
2028	1,648
Thereafter	1,600
Total future purchase commitments	$	25,207

Minimum Purchase Commitments

We enter into service agreements with our transload and transportation providers as well as commodity suppliers. Some of these agreements require us to purchase a minimum amount of services over a specific period of time. Any inability to meet these minimum contract requirements requires us to pay a shortfall fee, which is based on the difference between the minimum amount contracted for and the actual amount purchased.

Contingent Liability on Royalty Agreement

On May 17, 2017, we purchased reserves in Crane County, Texas, for $94.4 million cash plus contingent consideration. The contingent consideration is a royalty that is based on the tonnage shipped to third-parties. Because the contingent consideration is dependent on future tonnage sold, the amounts of which are uncertain, it is not currently possible to estimate the fair value of these future payments. The contingent consideration will be capitalized at the time a payment is probable and reasonably estimable, and the related depletion expense will be adjusted prospectively.

Other Commitments and Contingencies

Our operating subsidiary, U.S. Silica Company (“U.S. Silica”), has been named as a defendant in various product liability claims alleging silica exposure causing silicosis. During the three months ended March 31, 2024, no new claims were brought against U.S. Silica. As of March 31, 2024, there were 39 active silica-related product liability claims pending in which U.S. Silica is a defendant. Although the outcomes of these claims cannot be predicted with certainty, in the opinion of management, it is not reasonably possible that the ultimate resolution of these matters will have a material adverse effect on our financial position or results of operations that exceeds the accrual amounts.

We have recorded estimated liabilities for these claims in other long-term liabilities and an estimate of future recoveries under insurance in other assets on our consolidated balance sheets. For both March 31, 2024 and December 31, 2023, other non-current assets included zero for insurance for third-party product liability claims. As of both March 31, 2024 and December 31, 2023 other long-term liabilities included $0.9 million for third-party product liability claims.

Obligations under Guarantees

We have indemnified our insurers against any loss they may incur in the event that holders of surety bonds, issued on our behalf, execute the bonds. As of March 31, 2024, there was $55.8 million in bonds outstanding, of which $51.8 million related to reclamation requirements issued by various governmental authorities. Reclamation bonds remain outstanding until the mining area is reclaimed and the authority issues a formal release. The remaining bonds relate to licenses, permits, and tax collection.

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ 13,688	$ 44,648

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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+ Details

Equity-Based Compensation - Stock Options (Details) - $ / shares	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Number of Shares
Outstanding at the beginning (in shares)	349,080
Granted (in shares)	0	0
Exercised (in shares)	0	0
Forfeited (in shares)	0
Expired (in shares)	0
Outstanding at the end (in shares)	349,080		349,080
Exercisable (in shares)	349,080
Weighted Average Exercise Price
Outstanding at the beginning (in dollars per share)	$ 37.24
Granted (in dollars per share)	0
Exercised (in dollars per share)	0
Forfeited (in dollars per share)	0
Expired (in dollars per share)	0
Outstanding at the end (in dollars per share)	37.24		$ 37.24
Exercisable (in dollars per share)	$ 37.24
Weighted Average Remaining Contractual Term in Years
Outstanding at the beginning, Weighted Average Remaining Contractual Term in Years	10 months 24 days		1 year 1 month 6 days
Outstanding at the end, Weighted Average Remaining Contractual Term in Years	10 months 24 days		1 year 1 month 6 days
Exercisable, Weighted Average Remaining Contractual Term in Years	10 months 24 days

Revenue - Sales by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Total sales	$ 325,942	$ 442,240
Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total sales	183,172	300,013
Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total sales	142,770	142,227
Product
Disaggregation of Revenue [Line Items]
Total sales	261,794	344,014
Product \| Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total sales	119,024	201,787
Product \| Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total sales	142,770	142,227
Service
Disaggregation of Revenue [Line Items]
Total sales	64,148	98,226
Service \| Oil & Gas Proppants
Disaggregation of Revenue [Line Items]
Total sales	64,148	98,226
Service \| Industrial & Specialty Products
Disaggregation of Revenue [Line Items]
Total sales	$ 0	$ 0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-4

+ Details

Derivative Instruments

3 Months Ended

Mar. 31, 2024

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVE INSTRUMENTS

NOTE L—DERIVATIVE INSTRUMENTS

Cash Flow Hedges of Natural Gas Price Risk

Natural gas is the primary fuel source used for drying in the commercial silica production process. In the past, the price of natural gas has been volatile, and we believe this volatility may continue. In order to manage our exposure to natural gas price increases, we entered into natural gas swaps. The derivative instruments are recorded on the balance sheet within other current or long-term assets or liabilities based on maturity dates at their fair values. As of March 31, 2024, the fair value of our natural gas swaps was a liability of $1.8 million, of which $1.7 million was classified within accounts payable and accrued liabilities on our balance sheet and $0.1 million was classified within other long-term obligations on our balance sheet. At December 31, 2023, the fair value of our natural gas swaps was a liability of $1.9 million, of which $1.8 million was classified within accounts payable and accrued liabilities on our balance sheet and $0.1 million was classified within other long-term obligations on our balance sheet.

We designated the natural gas swap agreements as qualified cash flow hedges. Accordingly, the effective portion of the gain or loss on the derivative instrument was reported as a component of other comprehensive income and recognized in earnings in the same period or periods during which the hedged transaction affects earnings.


	March 31, 2024						December 31, 2023
	Maturity Date	Contract/Notional Amount (MMBtu)	Carrying Amount		Fair Value		Maturity Date	Contract/Notional Amount (MMBtu)	Carrying Amount		Fair Value

Natural Gas - W. Texas (WAHA) - Inside FERC	2024	870,000	$	(1,475)	$	(1,475)	2024	870,000	$	(1,542)	$	(1,542)
Natural Gas - W. Texas (WAHA) - Inside FERC	2024	750,000	$	—	$	—	2024	750,000	$	(11)	$	(11)

Natural Gas - Henry Hub - NYMEX	2024	120,000	$	(218)	$	(218)	2024	120,000	$	(258)	$	(258)
Natural Gas - Henry Hub - NYMEX	2025	90,000	$	(121)	$	(121)	2025	90,000	$	(115)	$	(115)

During the three months ended March 31, 2024, we had no ineffectiveness for the natural gas swap derivatives.

The following table summarizes the effect of derivative instruments (in thousands) on our income statements and our consolidated statements of comprehensive income:


	Three Months Ended March 31,
	2024		2023
Deferred losses from derivatives in OCI, beginning of period	$	(1,460)	$	(2,342)
Gain (loss) recognized in OCI from derivative instruments	84		(969)
Deferred losses from derivatives in OCI, end of period	$	(1,376)	$	(3,311)

Organization and Basis of Presentation	3 Months Ended
Organization and Basis of Presentation	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND BASIS OF PRESENTATION	NOTE A—ORGANIZATION AND BASIS OF PRESENTATION Organization U.S. Silica Holdings, Inc. (“Holdings,” and together with its subsidiaries “we,” “us” or the “Company”) is a global performance materials company and a leading producer of commercial silica used in the oil and gas industry and in a wide range of industrial applications. In addition, through our subsidiary EP Minerals, LLC ("EPM"), we are an industry leader in the production of industrial minerals, including diatomaceous earth, clay (calcium bentonite and calcium montmorillonite) and perlite. During our 124-year history, we have developed core competencies in mining, processing, logistics and materials science that enable us to produce and cost-effectively deliver products to customers across our end markets. Our operations are organized into two reportable segments based on end markets served: (1) Oil & Gas Proppants and (2) Industrial & Specialty Products. See Note T - Segment Reporting for more information on our reportable segments. Basis of Presentation and Consolidation The accompanying unaudited Condensed Consolidated Financial Statements as of and for the three months ended March 31, 2024 included in this Quarterly Report on Form 10-Q have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X issued by the U.S. Securities and Exchange Commission (“SEC”). They do not contain certain information included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2023; therefore, the unaudited Condensed Consolidated Financial Statements should be read in conjunction with that Annual Report on Form 10-K. Operating results for the three-month period ended March 31, 2024 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2024. In the opinion of management, all adjustments necessary for a fair presentation have been included. Such adjustments are of a normal, recurring nature. The unaudited Condensed Consolidated Financial Statements include the accounts of Holdings and its direct and indirect wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. Throughout this report we refer to (i) our unaudited Condensed Consolidated Balance Sheets as our “Balance Sheets,” (ii) our unaudited Condensed Consolidated Statements of Operations as our “Income Statements,” and (iii) our unaudited Condensed Consolidated Statements of Cash Flows as our “Cash Flows.”

Revenue - Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Unbilled Receivables
Beginning Balance	$ 0	$ 0
Reclassifications to billed receivables	0	0
Revenues recognized in excess of period billings	159	0
Ending Balance	159	0
Deferred Revenue
Beginning Balance	15,512	30,752
Revenues recognized from balances held at the beginning of the period	(1,830)	(5,569)
Revenues deferred from period collections on unfulfilled performance obligations	0	0
Revenues recognized from period collections	0	0
Ending Balance	$ 13,682	$ 25,183

Revenue - Foreign Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Total sales	$ 325,942	$ 442,240
Pre-tax income	18,356	58,145
Net income	13,688	44,648
Foreign Operations
Disaggregation of Revenue [Line Items]
Total sales	21,470	29,932
Pre-tax income	6,947	6,902
Net income	$ 5,488	$ 5,452

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

Goodwill and Intangible Assets

3 Months Ended

Mar. 31, 2024

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND INTANGIBLE ASSETS

NOTE H—GOODWILL AND INTANGIBLE ASSETS

The changes in the carrying amount of goodwill (in thousands) by business segment consisted of the following:


	Oil & Gas Proppants Segment		Industrial & Specialty Products Segment		Total
Balance at December 31, 2023	$	—	$	185,649	$	185,649
Impairment loss	—		—		—
Balance at March 31, 2024	$	—	$	185,649	$	185,649

Goodwill and trade names are evaluated for impairment annually as of October 31, or more frequently when indicators of impairment exist. We evaluated events and circumstances since the date of our last qualitative assessment, including macroeconomic conditions, industry and market conditions, and our overall financial performance. There were no triggering events during the first three months of 2024, therefore, no impairment charges were recorded related to goodwill or trade names for the three months ended March 31, 2024.

The changes in the carrying amount of intangible assets (in thousands) consisted of the following:


	March 31, 2024				December 31, 2023
	Gross Carrying Amount		Accumulated Amortization		Net		Gross Carrying Amount		Accumulated Amortization		Net

Technology and intellectual property	$	72,015	$	(36,123)	$	35,892	$	71,936	$	(34,894)	$	37,042
Customer relationships	66,999		(38,798)		28,201		66,999		(37,597)		29,402
Total definite-lived intangible assets:	$	139,014	$	(74,921)	$	64,093	$	138,935	$	(72,491)	$	66,444
Trade names	64,240		—		64,240		64,240		—		64,240
Other	700		—		700		700		—		700
Total intangible assets:	$	203,954	$	(74,921)	$	129,033	$	203,875	$	(72,491)	$	131,384

Estimated useful life of technology and intellectual property is 15 years. Estimated useful life of customer relationships is a range of 13 - 20 years.

Amortization expense was $2.4 million for both the three months ended March 31, 2024 and 2023.

The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows:


2024 (remaining nine months)	$	7,293
2025	$	9,721
2026	$	9,721
2027	$	9,721
2028	$	9,682

Pension and Post-Retirement Benefits

3 Months Ended

Mar. 31, 2024

Retirement Benefits [Abstract]

PENSION AND POST-RETIREMENT BENEFITS

NOTE O—PENSION AND POST-RETIREMENT BENEFITS

We maintain a single-employer noncontributory defined benefit pension plan covering certain employees. The plan is frozen to all new employees. The plan provides benefits based on each covered employee’s years of qualifying service. Our funding policy is to contribute amounts within the range of the minimum required and maximum deductible contributions for the plan consistent with a goal of appropriate minimization of the unfunded projected benefit obligations. The pension plan uses a benefit level per year of service for covered hourly employees and a final average pay method for covered salaried employees. The plan uses the projected unit credit cost method to determine the actuarial valuation.

In addition, we provide defined benefit post-retirement health care and life insurance benefits to some employees. Covered employees become eligible for these benefits at retirement after meeting minimum age and service requirements. The projected future cost of providing post-retirement benefits, such as healthcare and life insurance, is recognized as an expense as employees render services. In general, retiree health benefits are paid as covered expenses are incurred. Expenses incurred other than service costs are reported in Other (expense) income in our Condensed Consolidated Statements of Operations.

Net pension benefit cost (in thousands) consisted of the following:


	Three Months Ended March 31,
	2024		2023
Service cost	$	483	$	573
Interest cost	1,084		1,248
Expected return on plan assets	(1,159)		(1,519)
Net amortization and deferral	13		(2)
Net pension benefit costs	$	421	$	300

Net post-retirement benefit cost (in thousands) consisted of the following:


	Three Months Ended March 31,
	2024		2023
Service cost	$	2	$	4
Interest cost	79		80
Unrecognized prior service cost	(516)		(516)
Unrecognized net gain	(166)		(131)

Net post-retirement benefit income	$	(601)	$	(563)

We made no contributions to the qualified pension plan for the three months ended March 31, 2024 and 2023. Our best estimates of expected required contributions to the pension and post-retirement medical benefit plans for the 2024 fiscal year are $4.8 million and $0.9 million, respectively.

We contribute to three multiemployer defined benefit pension plans under the terms of collective-bargaining agreements for union-represented employees. A multiemployer plan is subject to collective bargaining for employees of two or more unrelated companies. These plans allow multiple employers to pool their pension resources and realize efficiencies associated with the daily administration of the plan. Multiemployer plans are generally governed by a board of trustees composed of management and labor representatives and are funded through employer contributions. However, in most cases, management is not directly represented. Our contributions to individual multiemployer pension funds did not exceed 5% of the fund’s total contributions for the three months ended March 31, 2024 and 2023. Additionally, our contributions to multiemployer post-retirement benefit plans were immaterial for all periods presented in the accompanying condensed consolidated financial statements.

We also sponsor a defined contribution plan covering certain employees. We contribute to the plan in two ways. For certain employees not covered by the defined benefit plan, we make a contribution equal to 4% of their salary. For all other eligible employees, we make a contribution up to 6% of eligible earnings. Contributions were $2.8 million and $2.1 million for the three months ended March 31, 2024 and 2023, respectively

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Inventory Disclosure [Abstract]
Supplies	$ 65,086	$ 65,422
Raw materials and work in process	53,315	54,142
Finished goods	21,134	29,865
Total inventories	$ 139,535	$ 149,429

Derivative Instruments - Narrative (Details) - USD ($)	3 Months Ended
Derivative Instruments - Narrative (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Interest Rate Cap \| Cash Flow Hedges
Derivative [Line Items]
Fair Value	$ 1,800,000	$ 1,900,000
Interest Rate Cap \| Cash Flow Hedges \| Accounts Payables and Accrued Liabilities
Derivative [Line Items]
Fair Value	1,700,000	1,800,000
Interest Rate Cap \| Cash Flow Hedges \| Other Long-term Obligations
Derivative [Line Items]
Fair Value	100,000	$ 100,000
Interest Rate Swap
Derivative [Line Items]
Ineffectiveness for interest rate swap derivatives	$ 0

Leases - Supplemental Balance Sheet Information (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Leases [Abstract]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Total leased assets	Total leased assets
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Total leased assets	Total leased assets
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current portion of long-term debt	Current portion of long-term debt
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term debt, net	Long-term debt, net
Assets
Operating	$ 38,859	$ 37,890
Finance	2,819	3,205
Total leased assets	41,678	41,095
Current
Operating	17,753	18,569
Finance	973	1,147
Non-current
Operating	53,912	55,089
Finance	1,711	1,961
Total lease liabilities	$ 74,349	$ 76,766
Weighted average remaining lease term:
Operating	6 years 1 month 6 days	6 years 2 months 12 days
Finance	5 years 1 month 6 days	4 years 9 months 18 days
Weighted average discount rate:
Operating	7.00%	6.30%
Finance	8.00%	6.60%

Accumulated Other Comprehensive Income (Loss)

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)

NOTE D—ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)

Accumulated other comprehensive income (loss) consists of fair value adjustments associated with cash flow hedges, accumulated adjustments for net experience losses and prior service costs related to employee benefit plans and foreign currency translation adjustments, net of tax. The following table presents the changes in accumulated other comprehensive income (loss) by component (in thousands):


	For the Three Months Ended March 31, 2024
	Unrealized (loss) gain on natural gas swaps		Foreign currency translation adjustments		Pension and other post-retirement benefits liability		Total
Beginning Balance	$	(1,460)	$	(981)	$	2,316	$	(125)
Other comprehensive income (loss) before reclassifications	84		(144)		3,311		3,251
Amounts reclassified from accumulated other comprehensive income	—		—		(503)		(503)
Ending Balance	$	(1,376)	$	(1,125)	$	5,124	$	2,623

Any amounts reclassified from accumulated other comprehensive income (loss) related to pension and other post-retirement benefits are included in the computation of net periodic benefit costs at their pre-tax amounts.

Pension and Post-Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2024

Retirement Benefits [Abstract]

Schedule of Net Pension and Post-Retirement Benefit Plans

Net pension benefit cost (in thousands) consisted of the following:


	Three Months Ended March 31,
	2024		2023
Service cost	$	483	$	573
Interest cost	1,084		1,248
Expected return on plan assets	(1,159)		(1,519)
Net amortization and deferral	13		(2)
Net pension benefit costs	$	421	$	300

Net post-retirement benefit cost (in thousands) consisted of the following:


	Three Months Ended March 31,
	2024		2023
Service cost	$	2	$	4
Interest cost	79		80
Unrecognized prior service cost	(516)		(516)
Unrecognized net gain	(166)		(131)

Net post-retirement benefit income	$	(601)	$	(563)

Property, Plant and Mine Development (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment
Property, plant and mine development, gross	$ 2,345,663	$ 2,336,480
Accumulated depreciation, depletion, amortization and impairment charges	(1,238,311)	(1,211,260)
Total property, plant and mine development, net	1,107,352	1,125,220
Mining property and mine development
Property, Plant and Equipment
Property, plant and mine development, gross	799,120	793,582
Asset retirement cost
Property, Plant and Equipment
Property, plant and mine development, gross	16,550	14,728
Land
Property, Plant and Equipment
Property, plant and mine development, gross	53,100	53,100
Land improvements
Property, Plant and Equipment
Property, plant and mine development, gross	87,618	87,618
Buildings
Property, Plant and Equipment
Property, plant and mine development, gross	77,294	76,691
Machinery and equipment
Property, Plant and Equipment
Property, plant and mine development, gross	1,259,972	1,253,734
Furniture and fixtures
Property, Plant and Equipment
Property, plant and mine development, gross	3,017	2,841
Construction-in-progress
Property, Plant and Equipment
Property, plant and mine development, gross	$ 48,992	$ 54,186

Derivative Instruments - Estimated Fair Values of Derivative Instruments (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($) MMBTU	Dec. 31, 2023 USD ($) MMBTU
Natural Gas - W. Texas (WAHA) - Inside FERC
Derivative Instruments, Gain (Loss)
Contract/Notional Amount (MMBtu) \| MMBTU	870,000	870,000
Carrying Amount	$ (1,475)	$ (1,542)
Fair Value	$ (1,475)	$ (1,542)
Natural Gas - W. Texas (WAHA) - Inside FERC
Derivative Instruments, Gain (Loss)
Contract/Notional Amount (MMBtu) \| MMBTU	750,000	750,000
Carrying Amount	$ 0	$ (11)
Fair Value	$ 0	$ (11)
Natural Gas - Henry Hub - NYMEX
Derivative Instruments, Gain (Loss)
Contract/Notional Amount (MMBtu) \| MMBTU	120,000	120,000
Carrying Amount	$ (218)	$ (258)
Fair Value	$ (218)	$ (258)
Natural Gas - Henry Hub - NYMEX
Derivative Instruments, Gain (Loss)
Contract/Notional Amount (MMBtu) \| MMBTU	90,000	90,000
Carrying Amount	$ (121)	$ (115)
Fair Value	$ (121)	$ (115)

Income Taxes (Details) - USD ($)	3 Months Ended
Income Taxes (Details) - USD ($)	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 4,775,000	$ 13,573,000
Effective tax rate (as a percent)	26.00%	23.00%
Effective tax rate without the effects of discrete tax items	24.00%	26.00%
Tax expense (benefit) related equity compensation	$ 0	$ 2,300,000

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Goodwill and Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2024

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Carrying Amount of Goodwill by Business Segment

The changes in the carrying amount of goodwill (in thousands) by business segment consisted of the following:


	Oil & Gas Proppants Segment		Industrial & Specialty Products Segment		Total
Balance at December 31, 2023	$	—	$	185,649	$	185,649
Impairment loss	—		—		—
Balance at March 31, 2024	$	—	$	185,649	$	185,649

Schedule of Changes in the Carrying Amount of Definite-Lived Intangible Assets

The changes in the carrying amount of intangible assets (in thousands) consisted of the following:


	March 31, 2024				December 31, 2023
	Gross Carrying Amount		Accumulated Amortization		Net		Gross Carrying Amount		Accumulated Amortization		Net

Technology and intellectual property	$	72,015	$	(36,123)	$	35,892	$	71,936	$	(34,894)	$	37,042
Customer relationships	66,999		(38,798)		28,201		66,999		(37,597)		29,402
Total definite-lived intangible assets:	$	139,014	$	(74,921)	$	64,093	$	138,935	$	(72,491)	$	66,444
Trade names	64,240		—		64,240		64,240		—		64,240
Other	700		—		700		700		—		700
Total intangible assets:	$	203,954	$	(74,921)	$	129,033	$	203,875	$	(72,491)	$	131,384

Schedule of Changes in the Carrying Amount of Indefinite-Lived Intangible Assets

The changes in the carrying amount of intangible assets (in thousands) consisted of the following:


	March 31, 2024				December 31, 2023
	Gross Carrying Amount		Accumulated Amortization		Net		Gross Carrying Amount		Accumulated Amortization		Net

Technology and intellectual property	$	72,015	$	(36,123)	$	35,892	$	71,936	$	(34,894)	$	37,042
Customer relationships	66,999		(38,798)		28,201		66,999		(37,597)		29,402
Total definite-lived intangible assets:	$	139,014	$	(74,921)	$	64,093	$	138,935	$	(72,491)	$	66,444
Trade names	64,240		—		64,240		64,240		—		64,240
Other	700		—		700		700		—		700
Total intangible assets:	$	203,954	$	(74,921)	$	129,033	$	203,875	$	(72,491)	$	131,384

Schedule of Estimated Amortization Expense Related to Definite-Lived Intangible Assets

The estimated amortization expense related to definite-lived intangible assets (in thousands) for the five succeeding years is as follows:


2024 (remaining nine months)	$	7,293
2025	$	9,721
2026	$	9,721
2027	$	9,721
2028	$	9,682

- Definition

Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482548/350-20-55-24

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1A

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-2

+ Details

Revenue (Tables)

3 Months Ended

Mar. 31, 2024

Revenue from Contract with Customer [Abstract]

Schedule of Sales by Major Source

The following table disaggregates our sales by major source (in thousands):


	Three Months Ended March 31, 2024						Three Months Ended March 31, 2023
Category	Oil & Gas Proppants		Industrial & Specialty Products		Total Sales		Oil & Gas Proppants		Industrial & Specialty Products		Total Sales
Product	$	119,024	$	142,770	$	261,794	$	201,787	$	142,227	$	344,014
Service	64,148		—		64,148		98,226		—		98,226
Total Sales	$	183,172	$	142,770	$	325,942	$	300,013	$	142,227	$	442,240

Schedule of Changes in Contract Assets and Liabilities

The following tables reflect the changes in our contract assets, which we classify as unbilled receivables and our contract liabilities, which we classify as deferred revenues, for the three months ended March 31, 2024 and 2023 (in thousands):


	Unbilled Receivables
	March 31, 2024		March 31, 2023
Beginning Balance	$	—	$	—
Reclassifications to billed receivables	—		—
Revenues recognized in excess of period billings	159		—
Ending Balance	$	159	$	—


	Deferred Revenue
	March 31, 2024		March 31, 2023
Beginning Balance	$	15,512	$	30,752
Revenues recognized from balances held at the beginning of the period	(1,830)		(5,569)
Revenues deferred from period collections on unfulfilled performance obligations	—		—
Revenues recognized from period collections	—		—
Ending Balance	$	13,682	$	25,183

Schedule of Total Sales, Pre-tax Income and Net Income Related to Foreign Operations

The following table includes information related to our foreign operations (in thousands):


	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Total Sales	$	21,470	$	29,932
Pre-tax income	$	6,947	$	6,902
Net income	$	5,488	$	5,452

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2024
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	NOTE U— SUBSEQUENT EVENTS On April 26, 2024, the Company entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Star Holding LLC, a Delaware limited liability company (“Parent”), and Star Merger Co., a Delaware corporation and a wholly owned subsidiary of Parent (“Merger Sub”), pursuant to which Parent will acquire all of the Company’s outstanding common shares, par value $0.01 per share (the “Common Stock”). Parent and Merger Sub are affiliates of funds managed by affiliates of Apollo Global Management, Inc. Pursuant to the transactions contemplated by the Merger Agreement, each outstanding share of the Company’s Common Stock (other than certain shares specified in the Merger Agreement) will be converted into the right to receive $15.50 per share of Common Stock in cash, without interest and less any required withholding taxes (the “Merger Consideration”). Consummation of the Merger is subject to certain customary conditions, including approval by the Company’s stockholders and receipt of required regulatory approvals. The Merger Agreement contains customary termination rights for the Company and Parent, which were described in the Company’s Current Report on Form 8-K filed on April 26, 2024. The Merger Agreement also contains customary representations, warranties and covenants of the Company, including covenants to conduct its business in the ordinary course during the interim period between the execution of the Merger Agreement and consummation of the Merger and not to engage in certain types of transactions during this interim period without the prior written consent of Parent. The terms of the Merger Agreement do not impact the Company’s consolidated financial statements as of and for the quarter ended March 31, 2024. We evaluated subsequent events through the date the consolidated financial statements were available for issuance and did not identify any additional events requiring disclosure.

Subsequent Events (Details) - Subsequent Event - Star Holding LLC - Merger Agreement	Apr. 26, 2024 $ / shares
Subsequent Event
Share price (in dollars per share)	$ 0.01
Conversion price (in dollars per share)	$ 15.50

Leases

3 Months Ended

Mar. 31, 2024

Leases [Abstract]

LEASES

NOTE P— LEASES

We lease railroad cars, office space, mining property, mining/processing equipment and transportation and other equipment. The majority of our leases have remaining lease terms of approximately one year to 20 years. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. We have lease agreements with lease and non-lease components, the latter of which are generally accounted for separately.

Supplemental balance sheet information related to leases was as follows (in thousands, except lease term and discount rate):


Leases	Classification	March 31, 2024		December 31, 2023
Assets
Operating	Lease right-of-use assets	$	38,859	$	37,890
Finance	Lease right-of-use assets	2,819		3,205
Total leased assets		$	41,678	$	41,095
Liabilities
Current
Operating	Current portion of operating lease liabilities	$	17,753	$	18,569
Finance	Current portion of long-term debt	973		1,147
Non-current
Operating	Operating lease liabilities	53,912		55,089
Finance	Long-term debt, net	1,711		1,961
Total lease liabilities		$	74,349	$	76,766

Lease Term and Discount Rate
Weighted average remaining lease term:
Operating		6.1 years		6.2 years
Finance		5.1 years		4.8 years

Weighted average discount rate:
Operating		7.0%		6.3%
Finance		8.0%		6.6%

The components of lease expense (in thousands) were as follows:


Lease Costs	Classification	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Operating lease costs(1)	Cost of sales	$	9,108	$	10,443
Operating lease costs(2)	Selling, general and administrative	419		595
Total (3)		$	9,527	$	11,038


(1) Included short-term operating lease costs of $4.9 million and $6.8 million for the three months ended March 31, 2024 and 2023, respectively.
(2) Included short-term operating lease costs of $0.1 million and $0.3 million for the three months ended March 31, 2024 and 2023 respectively.
(3) Not included were expenses for finance leases of $0.3 million and $0.2 million for the three months ended March 31, 2024 and 2023,respectively.

Supplemental cash flow information (in thousands) related to leases was as follows:


	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$	6,609	$	6,503
Financing cash flows for finance leases	$	478	$	268

Right-of-use assets obtained in exchange for new lease liabilities:
Operating leases	$	5,085	$	472
Finance leases	$	—	$	—

Maturities of lease liabilities (in thousands) as of March 31, 2024:


	Operating leases		Finance leases
2024 (remaining nine months)	$	17,349	$	863
2025	17,960		1,060
2026	14,089		896
2027	10,497		46
2028	8,255		46
Thereafter	21,687		144
Total lease payments	$	89,837	$	3,055
Less: Interest	16,540		371
Less: Other operating expenses	1,632		—
Total	$	71,665	$	2,684

LEASES

NOTE P— LEASES

Supplemental balance sheet information related to leases was as follows (in thousands, except lease term and discount rate):


Leases	Classification	March 31, 2024		December 31, 2023
Assets
Operating	Lease right-of-use assets	$	38,859	$	37,890
Finance	Lease right-of-use assets	2,819		3,205
Total leased assets		$	41,678	$	41,095
Liabilities
Current
Operating	Current portion of operating lease liabilities	$	17,753	$	18,569
Finance	Current portion of long-term debt	973		1,147
Non-current
Operating	Operating lease liabilities	53,912		55,089
Finance	Long-term debt, net	1,711		1,961
Total lease liabilities		$	74,349	$	76,766

Lease Term and Discount Rate
Weighted average remaining lease term:
Operating		6.1 years		6.2 years
Finance		5.1 years		4.8 years

Weighted average discount rate:
Operating		7.0%		6.3%
Finance		8.0%		6.6%

The components of lease expense (in thousands) were as follows:


Lease Costs	Classification	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Operating lease costs(1)	Cost of sales	$	9,108	$	10,443
Operating lease costs(2)	Selling, general and administrative	419		595
Total (3)		$	9,527	$	11,038


(1) Included short-term operating lease costs of $4.9 million and $6.8 million for the three months ended March 31, 2024 and 2023, respectively.
(2) Included short-term operating lease costs of $0.1 million and $0.3 million for the three months ended March 31, 2024 and 2023 respectively.
(3) Not included were expenses for finance leases of $0.3 million and $0.2 million for the three months ended March 31, 2024 and 2023,respectively.

Supplemental cash flow information (in thousands) related to leases was as follows:


	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$	6,609	$	6,503
Financing cash flows for finance leases	$	478	$	268

Right-of-use assets obtained in exchange for new lease liabilities:
Operating leases	$	5,085	$	472
Finance leases	$	—	$	—

Maturities of lease liabilities (in thousands) as of March 31, 2024:


	Operating leases		Finance leases
2024 (remaining nine months)	$	17,349	$	863
2025	17,960		1,060
2026	14,089		896
2027	10,497		46
2028	8,255		46
Thereafter	21,687		144
Total lease payments	$	89,837	$	3,055
Less: Interest	16,540		371
Less: Other operating expenses	1,632		—
Total	$	71,665	$	2,684

Equity-Based Compensation

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

EQUITY-BASED COMPENSATION

NOTE M—EQUITY-BASED COMPENSATION

In July 2011, we adopted the U.S. Silica Holdings, Inc. 2011 Incentive Compensation Plan (the “2011 Plan”), which was amended and restated effective May 2015, amended and restated effective February 1, 2020, amended and restated effective May 13, 2021, amended and restated effective May 12, 2022 and amended and restated effective May 11, 2023. The 2011 Plan provides for grants of stock options, restricted stock, performance share units and other incentive-based awards. We believe our 2011 Plan aligns the interests of our employees and directors with those of our common stockholders. We use a combination of treasury stock and new shares, if necessary, to satisfy option exercises or vesting of restricted awards and performance share units.

Stock Options

The following table summarizes the status of, and changes in, our stock option awards during the three months ended March 31, 2024:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2023	349,080	$	37.24	1.1 years
Granted	—	$	—
Exercised	—	$	—
Forfeited	—	$	—
Expired	—	$	—
Outstanding at March 31, 2024	349,080	$	37.24	0.9 years
Exercisable at March 31, 2024	349,080	$	37.24	0.9 years

There were no grants of stock options during the three months ended March 31, 2024 and 2023.

There was no stock option exercise activity during the three months ended March 31, 2024 and 2023.

As of March 31, 2024 and 2023, there was no unrecognized compensation expense related to these options. We account for forfeitures as they occur.

Restricted Stock and Restricted Stock Unit Awards

The following table summarizes the status of, and changes in, our unvested restricted stock awards during the three months ended March 31, 2024:


	Number of Shares	Grant Date Weighted Average Fair Value
Unvested, December 31, 2023	1,253,979	$	11.33
Granted	832,615	$	10.76
Vested	(457,134)	$	10.49
Forfeited	(2,279)	$	11.73
Unvested, March 31, 2024	1,627,181	$	11.27

We granted 832,615 and 493,934 restricted stock and restricted stock unit awards during the three months ended March 31, 2024 and 2023, respectively. The fair value of the awards was based on the market price of our stock at date of grant.

We recognized $2.2 million and $1.6 million of equity-based compensation expense related to restricted stock and restricted stock units during the three months ended March 31, 2024 and 2023, respectively. As of March 31, 2024, there was $15.2 million of unrecognized compensation expense related to these restricted stock and restricted stock units, which is expected to be recognized over a weighted-average period of 2.3 years.

We also granted cash awards during the three months ended March 31, 2020. These awards vested over a period of three years and were settled in cash. As such, these awards were classified as liability instruments. We recognized zero and $0.3 million of expense related to these awards for the three months ended March 31, 2024 and 2023, respectively. The liability for these awards was included in accounts payable and other accrued expenses on our balance sheets. These awards were remeasured at fair value each reporting period with resulting changes reflected in our income statements. As of March 31, 2024, there was no unrecognized expense related to these awards.

Performance Share Unit Awards

The following table summarizes the status of, and changes in, our performance share unit awards during the three months ended March 31, 2024:


	Number of Shares	Grant Date Weighted Average Fair Value
Unvested, December 31, 2023	1,874,060	$	11.73
Granted	1,107,359	$	11.59
Vested	(973,529)	$	10.53
Forfeited/Cancelled	(74,572)	$	15.86
Unvested, March 31, 2024	1,933,318	$	12.10

We granted 1,107,359 and 1,289,980 performance share unit awards during the three months ended March 31, 2024 and 2023, respectively. A portion of these awards was measured against total shareholder return ("TSR"), and a portion was measured against adjusted free cash flow ("ACF") targets. The grant date weighted average fair value of these awards was estimated to be $11.59 and $9.53 for the three months ended March 31, 2024 and 2023, respectively.

The number of TSR measured units that will vest will depend on the percentage ranking of our TSR compared to the TSR for each of the companies in the peer group over the three year period from January 1, 2024 through December 31, 2026 for the 2024 grant, January 1, 2023 through December 31, 2025 for the 2023 grant, and January 1, 2022 through December 31, 2024 for the 2022 grant. The number of ACF measured units that will vest will be based on ACF achievement versus target. The ACF targets are set annually and are approved by the Board of Directors. The related compensation expense is recognized on a straight-line basis over the vesting period.

The grant date fair value for the TSR awards was estimated using a Monte Carlo simulation model. The Monte Carlo simulation model requires the use of highly subjective assumptions. Our key assumptions in the model included the price and the expected volatility of our common stock and our self-determined peer group companies’ stock, risk-free rate of interest, dividend yields and cross-correlations between our common stock and our self-determined peer group companies' stock.

We recognized $1.9 million and $1.7 million of compensation expense related to performance share unit awards during the three months ended March 31, 2024 and 2023, respectively. As of March 31, 2024, there was $15.3 million of unrecognized compensation expense related to these performance share unit awards, which is expected to be recognized over a weighted-average period of 2.3 years.

We also granted cash awards during the three months ended March 31, 2020. These awards vested over a period of three years and were settled in cash. As such, these awards were classified as liability instruments. We recognized zero and $0.1 million of expense related to these awards for the three months ended March 31, 2024 and 2023, respectively. The liability for these awards was included in accounts payable and other accrued expenses on our balance sheets. These awards were remeasured at fair value each reporting period with resulting changes reflected in our income statements. As of March 31, 2024, there was no unrecognized expense related to these awards.

Debt - Narrative (Details)		3 Months Ended
Debt - Narrative (Details)	Mar. 23, 2023 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023	Mar. 31, 2023 USD ($)	Dec. 31, 2023
Debt Instrument [Line Items]
Debt issuance amortization		$ 615,000		$ 1,131,000
Insurance financing notes payable \| Notes Payable
Debt Instrument [Line Items]
Debt interest rate percentage			6.60%
Debt term			9 months
Notes payable amount		3,200,000
Revolver \| Revolver
Debt Instrument [Line Items]
Available borrowing base		$ 150,000,000
Interest rate		10.18%			10.21%
Amount drawn from borrowing base		$ 0
Amount available under the line of credit		$ 134,700,000
Actual consolidated leverage ratio		2.07
Letter of Credit \| Revolver
Debt Instrument [Line Items]
Amount allocated for letters of credit		$ 15,300,000
Senior Secured Credit Facility
Debt Instrument [Line Items]
Debt issued	$ 1,100,000,000
Capitalized debt issuance costs	45,900,000	$ 2,400,000
Loss on extinguishment of debt	4,300,000
Senior Secured Credit Facility \| Term Loan
Debt Instrument [Line Items]
Debt issued	950,000,000
Interest rate margins		0.75%
Repayments of debt		$ 25,000,000
Debt issuance amortization		$ 1,000,000
Senior Secured Credit Facility \| Term Loan \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Interest rate margins		4.00%
Senior Secured Credit Facility \| Term Loan \| Base Rate
Debt Instrument [Line Items]
Interest rate margins		3.00%
Senior Secured Credit Facility \| Revolver \| Revolver
Debt Instrument [Line Items]
Available borrowing base	$ 150,000,000
Credit facility consolidated total net leverage ratio, maximum	4.00
Credit facility consolidated total net leverage ratio, threshold borrowings outstanding, percent	35.00%

Accounts Receivable

3 Months Ended

Mar. 31, 2024

Receivables [Abstract]

ACCOUNTS RECEIVABLE

NOTE E—ACCOUNTS RECEIVABLE

Accounts receivable are recorded when billed or accrued and represent claims against third parties that will be settled in cash. The carrying value of our accounts receivable, net of the allowance for credit losses, represents their estimated net realizable value. Accounts receivable (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Trade receivables	$	192,998	$	190,189
Less: Allowance for credit losses	(4,324)		(5,323)
Net trade receivables	188,674		184,866
Other receivables	832		1,051
Total accounts receivable	$	189,506	$	185,917

We classify our trade receivables into the following portfolio segments: Oil & Gas Proppants and Industrial & Specialty Products, which also aligns with our reporting segments. We estimate the allowance for credit losses based on historical collection trends, the age of outstanding receivables, risks attributable to specific customers, such as credit history, bankruptcy or other going concern issues, and current economic and industry conditions. If events or circumstances indicate that specific receivable balances may be impaired, further consideration is given to the collectability of those balances and the allowance is adjusted accordingly. Past due balances are written off when we have exhausted our internal and external collection efforts and have been unsuccessful in collecting the amount due.

The following table reflects the change of the allowance for credit losses (in thousands):


	Oil & Gas Proppants		Industrial & Specialty Products		Total
Beginning balance, December 31, 2023	$	3,823	$	1,500	$	5,323
Allowance for credit losses	(700)		(328)		(1,028)
Recoveries	47		—		47
Write-offs	(18)		—		(18)
Ending balance, March 31, 2024	$	3,152	$	1,172	$	4,324

Our ten largest customers accounted for 47% and 45% of total sales for the three months ended March 31, 2024 and 2023, respectively. No customer accounted for 10% or more of our total sales for the three months ended March 31, 2024 or 2023. At March 31, 2024 and December 31, 2023, none of our customers' accounts receivable represented 10% or more of our total trade accounts receivable.

Commitments and Contingencies - Narrative (Details)		3 Months Ended
Commitments and Contingencies - Narrative (Details)	May 17, 2017 USD ($)	Mar. 31, 2024 USD ($) claim	Dec. 31, 2023 USD ($)
Loss Contingencies
Purchased reserves	$ 94,400,000
Number of new claims \| claim		0
Surety Bonds
Loss Contingencies
Surety bonds outstanding		$ 55,800,000
Reclamation Bonds
Loss Contingencies
Surety bonds outstanding		51,800,000
Other Non-current Assets
Loss Contingencies
Third party products claims liability under insurance in other long-term obligations		0	$ 0
Other Long-term Obligations
Loss Contingencies
Third party products claims liability under insurance in other long-term obligations		$ 900,000	$ 900,000
Pending Litigation
Loss Contingencies
Number of pending claims \| claim		39

Derivative Instruments - Effect of Derivative Instruments in Combined Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 855,527	$ 704,694
Gain (loss) recognized in OCI from derivative instruments	3,251
Ending Balance	870,325	741,557
Unrealized (loss) gain on natural gas swaps
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(1,460)	(2,342)
Gain (loss) recognized in OCI from derivative instruments	84	(969)
Ending Balance	$ (1,376)	$ (3,311)

- Definition

Amount of equity (deficit) attributable to parent and noncontrolling interest. Excludes temporary equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 24
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483421/250-10-45-24

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Section 45
-Paragraph 23
-Subparagraph (b)
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-URI https://asc.fasb.org//1943274/2147483421/250-10-45-23

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Section 45
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147479654/326-10-65-5

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 27: http://www.xbrl.org/2003/role/disclosureRef
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Reference 28: http://www.xbrl.org/2003/role/disclosureRef
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Reference 29: http://www.xbrl.org/2003/role/exampleRef
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Reference 30: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Equity-Based Compensation - Restricted Stock and Restricted Stock Units Awards (Details) - Restricted Stock and Restricted Stock Units - $ / shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Number of Shares
Unvested, beginning balance (in shares)	1,253,979
Granted (in shares)	832,615	493,934
Vested (in shares)	(457,134)
Forfeited (in shares)	(2,279)
Unvested, ending balance (in shares)	1,627,181
Grant Date Weighted Average Fair Value
Unvested, beginning balance (in dollars per share)	$ 11.33
Granted (in dollars per share)	10.76
Vested (in dollars per share)	10.49
Forfeited (in dollars per share)	11.73
Unvested, ending balance (in dollars per share)	$ 11.27

Equity-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Options Activity

The following table summarizes the status of, and changes in, our stock option awards during the three months ended March 31, 2024:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term in Years
Outstanding at December 31, 2023	349,080	$	37.24	1.1 years
Granted	—	$	—
Exercised	—	$	—
Forfeited	—	$	—
Expired	—	$	—
Outstanding at March 31, 2024	349,080	$	37.24	0.9 years
Exercisable at March 31, 2024	349,080	$	37.24	0.9 years

Schedule of Restricted Stock, Restricted Stock Unit and Performance Share Unit Awards Activity

The following table summarizes the status of, and changes in, our unvested restricted stock awards during the three months ended March 31, 2024:


	Number of Shares	Grant Date Weighted Average Fair Value
Unvested, December 31, 2023	1,253,979	$	11.33
Granted	832,615	$	10.76
Vested	(457,134)	$	10.49
Forfeited	(2,279)	$	11.73
Unvested, March 31, 2024	1,627,181	$	11.27

The following table summarizes the status of, and changes in, our performance share unit awards during the three months ended March 31, 2024:


	Number of Shares	Grant Date Weighted Average Fair Value
Unvested, December 31, 2023	1,874,060	$	11.73
Granted	1,107,359	$	11.59
Vested	(973,529)	$	10.53
Forfeited/Cancelled	(74,572)	$	15.86
Unvested, March 31, 2024	1,933,318	$	12.10

Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Earnings Per Share

The following table shows the computation of basic and diluted earnings per share:


In thousands, except per share amounts	Three Months Ended March 31,
	2024		2023
Numerator:
Net income attributable to U.S. Silica Holdings, Inc.	$	13,688	$	44,648

Denominator:
Weighted average shares outstanding	77,671		76,517
Diluted effect of stock awards	1,361		1,775
Weighted average shares outstanding assuming dilution	79,032		78,292

Earnings per share attributable to U.S. Silica Holdings, Inc.:
Basic earnings per share	$	0.18	$	0.58
Diluted earnings per share	$	0.17	$	0.57

Schedule of Potentially Dilutive Shares Excluded from Computation of Diluted Earnings Per Share

Certain stock options, restricted stock awards and performance share units were excluded from the computation of diluted earnings per share because their effect would have been anti-dilutive. Such potentially dilutive shares and stock awards excluded from the calculation of diluted earnings per common share were as follows:


In thousands	Three Months Ended March 31,
	2024	2023
Potentially dilutive shares excluded	—	—
Stock options excluded	349	445
Restricted stock and performance share unit awards excluded	50	50

Leases - Narrative (Details)	3 Months Ended
Leases - Narrative (Details)	Mar. 31, 2024
Minimum
Lessee, Lease, Description [Line Items]
Remaining term of lease contracts	1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining term of lease contracts	20 years

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating activities:
Net income	$ 13,581	$ 44,572
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	31,368	35,386
Debt issuance amortization	615	1,131
Original issue discount amortization	1,015	220
Deferred income taxes	(883)	8,899
Deferred revenue	(1,700)	(5,569)
Loss on disposal of property, plant and equipment	184	264
Equity-based compensation	4,051	3,286
Allowance for credit losses, net of recoveries	(1,028)	(186)
Other	8,212	8,024
Changes in operating assets and liabilities:
Accounts receivable	(2,561)	(17,578)
Inventories	9,895	(4,763)
Prepaid expenses and other current assets	4,561	3,657
Income taxes	5,386	4,308
Accounts payable and accrued expenses	(20,700)	(32,709)
Operating lease liabilities	(6,609)	(6,503)
Liability for pension and other post-retirement benefits	(4,037)	(433)
Other noncurrent assets and liabilities	(492)	(1,104)
Net cash provided by operating activities	40,858	40,902
Investing activities:
Capital expenditures	(12,410)	(18,929)
Capitalized intellectual property costs	(74)	(107)
Proceeds from sale of property, plant and equipment	169	105
Net cash used in investing activities	(12,315)	(18,931)
Financing activities:
Dividends paid	0	(1)
Tax payments related to shares withheld for vested restricted stock and stock units	(5,618)	(9,920)
Payments on short-term debt	(3,235)	(2,814)
Payments on long-term debt	(27,188)	(109,062)
Financing fees paid	(3,350)	(40,949)
Contributions from (distributions to) non-controlling interest	36	(350)
Principal payments on finance lease obligations	(423)	(226)
Net cash used in financing activities	(39,778)	(163,322)
Net decrease in cash and cash equivalents	(11,235)	(141,351)
Cash and cash equivalents, beginning of period	245,716	280,845
Cash and cash equivalents, end of period	234,481	139,494
Cash paid during the period for:
Interest	21,895	21,401
Taxes, net of refunds	122	354
Non-cash items:
Accrued capital expenditures	$ 4,505	$ 4,793

Earnings Per Share

3 Months Ended

Mar. 31, 2024

Earnings Per Share [Abstract]

EARNINGS PER SHARE

NOTE C—EARNINGS PER SHARE

Basic earnings per common share is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted earnings per common share is computed similarly to basic earnings per common share except that the weighted average number of common shares outstanding is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued.

Diluted net earnings per share assumes the conversion of contingently convertible securities and stock options under the treasury stock method, if dilutive. Contingently convertible securities and stock options are excluded from the calculation of fully diluted earnings per share if they are anti-dilutive, including when we incur a loss from continuing operations.

The following table shows the computation of basic and diluted earnings per share:


In thousands, except per share amounts	Three Months Ended March 31,
	2024		2023
Numerator:
Net income attributable to U.S. Silica Holdings, Inc.	$	13,688	$	44,648

Denominator:
Weighted average shares outstanding	77,671		76,517
Diluted effect of stock awards	1,361		1,775
Weighted average shares outstanding assuming dilution	79,032		78,292

Earnings per share attributable to U.S. Silica Holdings, Inc.:
Basic earnings per share	$	0.18	$	0.58
Diluted earnings per share	$	0.17	$	0.57

Potentially dilutive shares are excluded from the calculation of diluted weighted average shares outstanding and diluted earnings per share if we are in a net loss position. Certain stock options, restricted stock awards and performance share units were excluded from the computation of diluted earnings per share because their effect would have been anti-dilutive. Such potentially dilutive shares and stock awards excluded from the calculation of diluted earnings per common share were as follows:


In thousands	Three Months Ended March 31,
	2024	2023
Potentially dilutive shares excluded	—	—
Stock options excluded	349	445
Restricted stock and performance share unit awards excluded	50	50

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Tax benefit on unrealized loss on derivatives	$ 27	$ (309)
Tax expense (benefit) on foreign currency translation adjustment	(45)	71
Tax benefit on pension and other post-retirement benefits liability adjustment	$ 895	$ 7

Revenue

3 Months Ended

Mar. 31, 2024

Revenue from Contract with Customer [Abstract]

REVENUE

NOTE R— REVENUE

We consider sales disaggregated at the product and service level by business segment to depict how the nature, amount, timing and uncertainty of revenues and cash flow are impacted by changes in economic factors. The following table disaggregates our sales by major source (in thousands):


	Three Months Ended March 31, 2024						Three Months Ended March 31, 2023
Category	Oil & Gas Proppants		Industrial & Specialty Products		Total Sales		Oil & Gas Proppants		Industrial & Specialty Products		Total Sales
Product	$	119,024	$	142,770	$	261,794	$	201,787	$	142,227	$	344,014
Service	64,148		—		64,148		98,226		—		98,226
Total Sales	$	183,172	$	142,770	$	325,942	$	300,013	$	142,227	$	442,240


	Unbilled Receivables
	March 31, 2024		March 31, 2023
Beginning Balance	$	—	$	—
Reclassifications to billed receivables	—		—
Revenues recognized in excess of period billings	159		—
Ending Balance	$	159	$	—


	Deferred Revenue
	March 31, 2024		March 31, 2023
Beginning Balance	$	15,512	$	30,752
Revenues recognized from balances held at the beginning of the period	(1,830)		(5,569)
Revenues deferred from period collections on unfulfilled performance obligations	—		—
Revenues recognized from period collections	—		—
Ending Balance	$	13,682	$	25,183

We have elected to use the practical expedients allowed under ASC 606-10-50-14, pursuant to which we have excluded disclosures of transaction prices allocated to remaining performance obligations and when we expect to recognize such revenue. The majority of our remaining performance obligations are primarily comprised of unfulfilled product, transportation service, and labor service orders, all of which hold a remaining duration of less than one year. The long-term portion of deferred revenue primarily represents a combination of refundable and nonrefundable customer prepayments for which related current performance obligations do not yet exist, but are expected to arise, before the expiration of the contract. Our residual unfulfilled performance obligations are comprised primarily of long-term equipment rental arrangements in which we recognize revenues equal to what we have a right to invoice. Generally, no variable consideration exists related to our remaining performance obligations and no consideration is excluded from the associated transaction prices.

Foreign Operations

The following table includes information related to our foreign operations (in thousands):


	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Total Sales	$	21,470	$	29,932
Pre-tax income	$	6,947	$	6,902
Net income	$	5,488	$	5,452

Foreign operations constituted approximately $18.0 million and $36.9 million of consolidated assets as of March 31, 2024 and 2023, respectively.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

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+ Details

Related Party Transactions	3 Months Ended
Related Party Transactions	Mar. 31, 2024
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	NOTE S— RELATED PARTY TRANSACTIONS There were no related party transactions during the three months ended March 31, 2024 or 2023.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

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+ Details

Revenue - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total assets of VIE	$ 2,055,059	$ 2,096,593
Foreign Operations
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total assets of VIE	$ 18,000		$ 36,900
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining duration period of expected satisfaction of performance obligations (less than)	1 year

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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+ Details

Inventories (Tables)

3 Months Ended

Mar. 31, 2024

Inventory Disclosure [Abstract]

Schedule of Inventories

Inventories (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Supplies	$	65,086	$	65,422
Raw materials and work in process	53,315		54,142
Finished goods	21,134		29,865
Total inventories	$	139,535	$	149,429

Debt (Tables)

3 Months Ended

Mar. 31, 2024

Debt Disclosure [Abstract]

Schedule of Debt

Debt (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Senior secured credit facility:
Revolver expiring March 23, 2028 (10.18% at March 31, 2024 and 10.21% at December 31, 2023)	$	—	$	—
Term Loan—final maturity March 23, 2030 (9.33% at March 31, 2024 and 10.21% at December 31, 2023)	840,875		868,063
Less: Unamortized original issue discount	(24,598)		(24,183)
Less: Unamortized debt issuance cost	(12,733)		(13,421)
Insurance financing notes payable	3,235		6,470
Finance leases (See Note P - Leases)	2,684		3,108
Total debt	809,463		840,037
Less: current portion	(12,708)		(16,367)
Total long-term portion of debt	$	796,755	$	823,670

Schedule of Contractual Maturities of Term Loan

At March 31, 2024, contractual maturities of our Term Loan (in thousands) are as follows:


2024 (remaining nine months)	$	6,375
2025	8,500
2026	8,500
2027	8,500
2028	8,500
Thereafter	800,500
Total	$	840,875

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 13,581	$ 44,572
Other comprehensive income (loss):
Unrealized gain (loss) on derivatives (net of tax of $27 and $(309)) for the three months ended March 31, 2024 and 2023, respectively.	84	(969)
Foreign currency translation adjustment (net of tax of $(45) and $71) for the three months ended March 31, 2024 and 2023, respectively.	(144)	222
Pension and other post-retirement benefits liability adjustment (net of tax of $895 and $7) for the three months ended March 31, 2024 and 2023, respectively.	2,808	22
Comprehensive income	16,329	43,847
Less: Comprehensive loss attributable to non-controlling interest	(107)	(76)
Comprehensive income attributable to U.S. Silica Holdings, Inc.	$ 16,436	$ 43,923

- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References + Details

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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+ Details

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Debt

3 Months Ended

Mar. 31, 2024

Debt Disclosure [Abstract]

DEBT

NOTE I—DEBT

Debt (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Senior secured credit facility:
Revolver expiring March 23, 2028 (10.18% at March 31, 2024 and 10.21% at December 31, 2023)	$	—	$	—
Term Loan—final maturity March 23, 2030 (9.33% at March 31, 2024 and 10.21% at December 31, 2023)	840,875		868,063
Less: Unamortized original issue discount	(24,598)		(24,183)
Less: Unamortized debt issuance cost	(12,733)		(13,421)
Insurance financing notes payable	3,235		6,470
Finance leases (See Note P - Leases)	2,684		3,108
Total debt	809,463		840,037
Less: current portion	(12,708)		(16,367)
Total long-term portion of debt	$	796,755	$	823,670

Senior Secured Credit Facility

On March 23, 2023, we entered into the Fourth Amended and Restated Credit Agreement (the "Credit Agreement"), by entering into a new $1.1 billion senior secured credit facility, consisting of a $950 million Term Loan (the "Term Loan") and a $150 million revolving credit facility (the "Revolver") (collectively the "Credit Facility") that may also be used for swingline loans or letters of credit, and we may elect to increase the term loan or the revolving credit facility in accordance with the terms of the Credit Agreement. Borrowings under the Credit Agreement will bear interest at variable rates as determined at our election, based on the Term Secured Overnight Financing Rate ("SOFR") or a base rate, in each case, plus an applicable margin. In addition, under the Credit Agreement, we are required to pay a per annum commitment fee to revolving lenders and fees for letters of credit. The Credit Agreement is secured by substantially all of our assets and our domestic subsidiaries' assets and a pledge of the equity interests in such entities. The Term Loan matures on March 23, 2030, and the Revolver expires March 23, 2028. We capitalized $45.9 million in debt issuance costs and original issue discount as a result of the Credit Agreement. Additionally, as a result of the exit of certain lending parties, a portion of debt issuance and original discount costs were written off which resulted in additional expense of approximately $4.3 million. This was recorded as a loss on the extinguishment of debt, which was recorded in Other (expense) income, net, including interest income in the Condensed Consolidated Statements of Operations.

During the first quarter of 2024, we entered into Amendment No. 1 to the Credit Agreement (the “Repricing Amendment”), which amends certain terms of the Credit Agreement. The Repricing Amendment reduces the applicable interest rate margins on the Term Loans by 75 basis points to 3.00% (for the Term Loans bearing interest at rates based on the base rate) and to 4.00% (for the Term Loans bearing interest at rates based on the SOFR). The Repricing Amendment also allows us to enter into a repricing transaction without prepayment premium if such repricing transaction occurs after September 25, 2024. The maturity dates of March 23, 2030 with respect to the Term Loans and March 23, 2028 with respect to the revolving credit facility and all other material provisions under the Credit Agreement remain unchanged. We capitalized approximately $2.4 million of debt issuance costs and original issue discount as a result of the Repricing Amendment.

In conjunction with the Repricing Amendment, we completed a voluntary Term Loan principal repayment of $25 million. A proportionate share of debt issuance and original discount costs were written off in conjunction with the prepayments of this debt which resulted in additional expense of $1.0 million. These expenses were recorded in Other (expense) income, net, including interest income in the Consolidated Statements of Operations.

The Credit Facility contains covenants that, among other things, limit our ability, and certain of our subsidiaries' abilities, to create, incur or assume indebtedness and liens, to make acquisitions or investments, to sell assets and to pay dividends. The Credit Agreement also requires us to maintain a consolidated leverage ratio of no more than 4.00:1.00 as of the last day of any fiscal quarter whenever usage of the Revolver (other than certain undrawn letters of credit) exceeds 35% of the Revolver commitment. These covenants are subject to a number of important exceptions and qualifications. The Credit Agreement includes events of default and other affirmative and negative covenants that are usual for facilities and transactions of this type. As of March 31, 2024 and December 31, 2023, we were in compliance with all covenants in accordance with our senior secured Credit Facility.

Term Loan

At March 31, 2024, contractual maturities of our Term Loan (in thousands) are as follows:


2024 (remaining nine months)	$	6,375
2025	8,500
2026	8,500
2027	8,500
2028	8,500
Thereafter	800,500
Total	$	840,875

Revolving Line-of-Credit

We have a $150.0 million Revolver with zero drawn and $15.3 million allocated for letters of credit as of March 31, 2024, leaving $134.7 million available under the Revolver. Based on our consolidated leverage ratio of 2.07:1.00 as of March 31, 2024, we have access to the full availability of the Revolver.

Insurance Financing Notes Payable

During the third quarter of 2023, we renewed our insurance policies and financed the payments through notes payable with a stated interest rate of 6.6%. These payments will be made in installments throughout a nine-month period and, as such, have been classified as current debt. As of March 31, 2024, the notes payable had a balance of $3.2 million.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

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+ Details

Goodwill and Intangible Assets - Estimated Amortization Expense Related to Definite-Lived Intangible Assets (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2024 (remaining nine months)	$ 7,293
2025	9,721
2026	9,721
2027	9,721
2028	$ 9,682

Goodwill and Intangible Assets - Carrying Amount of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 139,014	$ 138,935
Accumulated Amortization	(74,921)	(72,491)
Net	64,093	66,444
Total Intangible Assets
Gross Carrying Amount	203,954	203,875
Accumulated Amortization	(74,921)	(72,491)
Net	129,033	131,384
Trade names
Indefinite-lived Intangible Assets
Gross Carrying Amount	64,240	64,240
Other
Indefinite-lived Intangible Assets
Gross Carrying Amount	700	700
Technology and intellectual property
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	72,015	71,936
Accumulated Amortization	(36,123)	(34,894)
Net	35,892	37,042
Total Intangible Assets
Accumulated Amortization	(36,123)	(34,894)
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	66,999	66,999
Accumulated Amortization	(38,798)	(37,597)
Net	28,201	29,402
Total Intangible Assets
Accumulated Amortization	$ (38,798)	$ (37,597)

Pension and Post-Retirement Benefits - Net Pension and Post-Retirement Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	$ 483	$ 573
Interest cost	1,084	1,248
Expected return on plan assets	(1,159)	(1,519)
Net amortization and deferral	13	(2)
Net pension and post-retirement benefit costs (income)	421	300
Post-retirement Benefits
Pension Plans, Postretirement and Other Employee Benefits
Service cost	2	4
Interest cost	79	80
Unrecognized prior service cost	(516)	(516)
Unrecognized net gain	(166)	(131)
Net pension and post-retirement benefit costs (income)	$ (601)	$ (563)

Commitments and Contingencies - Future Minimum Annual Commitments (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Minimum Purchase Commitments
2024 (remaining nine months)	$ 8,730
2025	6,661
2026	4,520
2027	2,048
2028	1,648
Thereafter	1,600
Total future purchase commitments	$ 25,207

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Annual Commitments

Future Minimum Annual Commitments at March 31, 2024 (in thousands):


	Minimum Purchase Commitments
2024 (remaining nine months)	$	8,730
2025	6,661
2026	4,520
2027	2,048
2028	1,648
Thereafter	1,600
Total future purchase commitments	$	25,207

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2024
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE B—SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates and Assumptions The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the related disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. The areas requiring the use of management estimates and assumptions relate to the purchase price allocation for businesses acquired; mineral reserves that are the basis for future cash flow estimates utilized in impairment calculations and units-of-production amortization calculations; environmental, reclamation and closure obligations; estimates of recoverable minerals; estimates of allowance for credit losses; estimates of fair value for certain reporting units and asset impairments (including impairments of goodwill, intangible assets and other long-lived assets); write-downs of inventory to net realizable value; equity-based compensation expense; post-employment, post-retirement and other employee benefit liabilities; valuation allowances for deferred tax assets; contingent considerations; reserves for contingencies and litigation and the fair value and accounting treatment of financial instruments. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may differ significantly from these estimates under different assumptions or conditions. New Accounting Pronouncements Recently Adopted None. New Accounting Pronouncements Not Yet Adopted In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The amendments in this Update improve financial reporting by requiring disclosure of incremental segment information on an annual and interim basis for all public entities to enable investors to develop more decision-useful financial analyses. The amendments in this Update do not change or remove current disclosure requirements as required by Topic 280. The amendments in this Update also do not change how a public entity identifies its operating segments, aggregates those operating segments, or applies the quantitative thresholds to determine its reportable segments. The amendments in this Update are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Public entities will be required to apply the amendments in this Update retrospectively to all prior periods presented in the financial statements. We are currently evaluating the effect this guidance will have on our disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The amendments in this Update related to the rate reconciliation and income taxes paid disclosures improve the transparency of income tax disclosures by requiring (1) consistent categories and greater disaggregation of information in the rate reconciliation and (2) income taxes paid disaggregated by jurisdiction. The amendments allow investors to better assess, in their capital allocation decisions, how an entity’s worldwide operations and related tax risks and tax planning and operational opportunities affect its income tax rate and prospects for future cash flows. The other amendments in this Update improve the effectiveness and comparability of disclosures by (1) adding disclosures of pretax income (or loss) and income tax expense (or benefit) to be consistent with U.S. Securities and Exchange Commission (SEC) Regulation S-X 210.4-08(h), Rules of General Application—General Notes to Financial Statements: Income Tax Expense, and (2) removing disclosures that no longer are considered cost beneficial or relevant. The amendments in this Update are effective for annual periods beginning after December 15, 2024. We are currently evaluating the effect this guidance will have on our disclosures.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2024
Income Tax Disclosure [Abstract]
INCOME TAXES	NOTE Q— INCOME TAXES For interim period reporting, we record income taxes using an estimated annual effective tax rate based upon projected annual income, forecasted permanent tax differences, discrete items and statutory rates in states in which we operate. At the end of each interim period, we update the estimated annual effective tax rate, and if the estimated tax rate changes based on new information, we make a cumulative adjustment in the period. We record the tax effect of an unusual or infrequently occurring item in the interim period in which it occurs as a discrete item of tax. For the three months ended March 31, 2024 and 2023, we had tax expense of $4.8 million and $13.6 million, respectively. The effective tax rates were 26% and 23% for the three months ended March 31, 2024 and 2023, respectively. Without discrete items, which primarily consist of the tax impact of non-US income taxes, the effective tax rates for the three months ended March 31, 2024 and 2023 would have been 24% and 26%, respectively. During the three months ended March 31, 2024 and 2023, we recorded tax expense of zero and a tax benefit of $2.3 million, respectively, related to equity compensation. Historically, our actual effective tax rates have differed from the statutory effective rate primarily due to the benefit received from statutory percentage depletion allowances. The deduction for statutory percentage depletion does not necessarily change proportionately to changes in income before income taxes. For the three months ended March 31, 2024, the benefit received from statutory percentage depletion allowances was offset by nondeductible executive compensation and state income taxes.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
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-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2024	Apr. 19, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	001-35416
Entity Registrant Name	U.S. Silica Holdings, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-3718801
Entity Address, Address Line One	24275 Katy Freeway, Suite 600
Entity Address, City or Town	Katy
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77494
City Area Code	281
Local Phone Number	258-2170
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	SLCA
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		78,133,202
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001524741
Current Fiscal Year End Date	--12-31

Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net income attributable to U.S. Silica Holdings, Inc.	$ 13,688	$ 44,648
Net income attributable to U.S. Silica Holdings, Inc.	$ 13,688	$ 44,648
Denominator:
Weighted average shares outstanding (in shares)	77,671	76,517
Diluted effect of stock awards (in shares)	1,361	1,775
Weighted average shares outstanding assuming dilution (shares)	79,032	78,292
Earnings per share attributable to U.S. Silica Holdings, Inc.:
Basic earnings per share (in dollars per share)	$ 0.18	$ 0.58
Diluted earnings per share (in dollars per share)	$ 0.17	$ 0.57

Segment Reporting - Narrative (Details)	3 Months Ended
Segment Reporting - Narrative (Details)	Mar. 31, 2024 USD ($) segment product	Dec. 31, 2023 USD ($)
Segment Reporting Information
Number of reportable segments \| segment	2
Number of product types (over) \| product	800
Goodwill	$ 185,649,000	$ 185,649,000
Oil & Gas Proppants
Segment Reporting Information
Goodwill	0	0
Industrial & Specialty Products
Segment Reporting Information
Goodwill	$ 185,600,000	$ 185,600,000

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References + Details

Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Operating leases
2024 (remaining nine months)	$ 17,349
2025	17,960
2026	14,089
2027	10,497
2028	8,255
Thereafter	21,687
Total lease payments	89,837
Less: Interest	16,540
Less: Other operating expenses	1,632
Total	71,665
Finance leases
2024 (remaining nine months)	863
2025	1,060
2026	896
2027	46
2028	46
Thereafter	144
Total lease payments	3,055
Less: Interest	371
Less: Other operating expenses	0
Total	$ 2,684	$ 3,108

Equity-Based Compensation - Performance Share Awards (Details) - Performance Share Units - $ / shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Number of Shares
Unvested, beginning balance (in shares)	1,874,060
Granted (in shares)	1,107,359	1,289,980
Vested (in shares)	(973,529)
Forfeited/Cancelled (in shares)	(74,572)
Unvested, ending balance (in shares)	1,933,318
Grant Date Weighted Average Fair Value
Unvested, beginning balance (in dollars per share)	$ 11.73
Granted (in dollars per share)	11.59	$ 9.53
Vested (in dollars per share)	10.53
Forfeited/Cancelled (in dollars per share)	15.86
Unvested, ending balance (in dollars per share)	$ 12.10

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Lessee, Lease, Description [Line Items]
Total lease cost	$ 9,527	$ 11,038
Finance lease expense	300	200
Cost of sales
Lessee, Lease, Description [Line Items]
Total lease cost	9,108	10,443
Short-term operating lease costs	4,900	6,800
Selling, general and administrative
Lessee, Lease, Description [Line Items]
Total lease cost	419	595
Short-term operating lease costs	$ 100	$ 300

Earnings Per Share - Potentially Dilutive Shares Excluded From Calculation of Diluted Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Potentially dilutive shares excluded
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares excluded from calculation of weighted average shares outstanding and diluted earnings per share (in shares)	0	0
Stock options excluded
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares excluded from calculation of weighted average shares outstanding and diluted earnings per share (in shares)	349	445
Restricted stock and performance share unit awards excluded
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares excluded from calculation of weighted average shares outstanding and diluted earnings per share (in shares)	50	50

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ 6,609	$ 6,503
Financing cash flows for finance leases	478	268
Right-of-use assets obtained in exchange for new lease liabilities:
Operating leases	5,085	472
Finance leases	$ 0	$ 0

Related Party Transactions (Details) - USD ($)	3 Months Ended
Related Party Transactions (Details) - USD ($)	Mar. 31, 2024	Mar. 31, 2023
Related Party Transactions [Abstract]
Related party transaction, amounts of transaction	$ 0	$ 0

Accounts Receivable - Changes in Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Allowance for Doubtful Accounts Receivable Roll Forward
Beginning balance, December 31, 2023	$ 5,323
Allowance for credit losses	(1,028)	$ (186)
Recoveries	47
Write-offs	(18)
Ending balance, March 31, 2024	4,324
Oil & Gas Proppants
Allowance for Doubtful Accounts Receivable Roll Forward
Beginning balance, December 31, 2023	3,823
Allowance for credit losses	(700)
Recoveries	47
Write-offs	(18)
Ending balance, March 31, 2024	3,152
Industrial & Specialty Products
Allowance for Doubtful Accounts Receivable Roll Forward
Beginning balance, December 31, 2023	1,500
Allowance for credit losses	(328)
Recoveries	0
Write-offs	0
Ending balance, March 31, 2024	$ 1,172

Organization and Basis of Presentation (Details)	3 Months Ended
Organization and Basis of Presentation (Details)	Mar. 31, 2024 yr segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of years in business \| yr	124
Number of reportable segments \| segment	2

Segment Reporting - Sales and Segment Contribution Margin for Reporting Segments and Other Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information
Total sales	$ 325,942	$ 442,240
Total segment contribution margin	105,464	152,826
Operating activities excluded from segment cost of sales	(3,246)	(3,719)
Selling, general and administrative	(30,754)	(29,163)
Depreciation, depletion and amortization	(31,368)	(35,386)
Interest expense	(24,263)	(24,061)
Other income (expense), net, including interest income	2,523	(2,352)
Income tax expense	(4,775)	(13,573)
Net income	13,581	44,572
Less: Net loss attributable to non-controlling interest	(107)	(76)
Net income attributable to U.S. Silica Holdings, Inc.	13,688	44,648
Oil & Gas Proppants
Segment Reporting Information
Total sales	183,172	300,013
Total segment contribution margin	59,515	109,897
Industrial & Specialty Products
Segment Reporting Information
Total sales	142,770	142,227
Total segment contribution margin	$ 45,949	$ 42,929

Equity-Based Compensation - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants of stock options (in shares)	0	0
Exercised (in shares)	0	0
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 0	$ 0
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	832,615	493,934
Recognized equity-based compensation	$ 2,200,000	$ 1,600,000
Unrecognized compensation expense related to awards	$ 15,200,000
Recognized weighted-average period	2 years 3 months 18 days
Granted (in dollars per share)	$ 10.76
Restricted Stock and Restricted Stock Units Cash Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 0	$ 300,000
Award vesting period			3 years
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	1,107,359	1,289,980
Recognized equity-based compensation	$ 1,900,000	$ 1,700,000
Unrecognized compensation expense related to awards	$ 15,300,000
Recognized weighted-average period	2 years 3 months 18 days
Granted (in dollars per share)	$ 11.59	$ 9.53
Performance Share Units Cash Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized equity-based compensation	$ 0	$ 100,000
Award vesting period			3 years

Leases (Tables)

3 Months Ended

Mar. 31, 2024

Leases [Abstract]

Schedule of Supplemental Balance Sheet Information

Supplemental balance sheet information related to leases was as follows (in thousands, except lease term and discount rate):


Leases	Classification	March 31, 2024		December 31, 2023
Assets
Operating	Lease right-of-use assets	$	38,859	$	37,890
Finance	Lease right-of-use assets	2,819		3,205
Total leased assets		$	41,678	$	41,095
Liabilities
Current
Operating	Current portion of operating lease liabilities	$	17,753	$	18,569
Finance	Current portion of long-term debt	973		1,147
Non-current
Operating	Operating lease liabilities	53,912		55,089
Finance	Long-term debt, net	1,711		1,961
Total lease liabilities		$	74,349	$	76,766

Lease Term and Discount Rate
Weighted average remaining lease term:
Operating		6.1 years		6.2 years
Finance		5.1 years		4.8 years

Weighted average discount rate:
Operating		7.0%		6.3%
Finance		8.0%		6.6%

Schedule of Components of Lease Expense and Supplemental Cash Flow Information

The components of lease expense (in thousands) were as follows:


Lease Costs	Classification	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Operating lease costs(1)	Cost of sales	$	9,108	$	10,443
Operating lease costs(2)	Selling, general and administrative	419		595
Total (3)		$	9,527	$	11,038


(1) Included short-term operating lease costs of $4.9 million and $6.8 million for the three months ended March 31, 2024 and 2023, respectively.
(2) Included short-term operating lease costs of $0.1 million and $0.3 million for the three months ended March 31, 2024 and 2023 respectively.
(3) Not included were expenses for finance leases of $0.3 million and $0.2 million for the three months ended March 31, 2024 and 2023,respectively.

Supplemental cash flow information (in thousands) related to leases was as follows:


	Three Months Ended March 31, 2024		Three Months Ended March 31, 2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$	6,609	$	6,503
Financing cash flows for finance leases	$	478	$	268

Right-of-use assets obtained in exchange for new lease liabilities:
Operating leases	$	5,085	$	472
Finance leases	$	—	$	—

Schedule of Maturity of Operating Lease Liabilities

Maturities of lease liabilities (in thousands) as of March 31, 2024:


	Operating leases		Finance leases
2024 (remaining nine months)	$	17,349	$	863
2025	17,960		1,060
2026	14,089		896
2027	10,497		46
2028	8,255		46
Thereafter	21,687		144
Total lease payments	$	89,837	$	3,055
Less: Interest	16,540		371
Less: Other operating expenses	1,632		—
Total	$	71,665	$	2,684

Schedule of Maturity of Finance Lease Liabilities

Maturities of lease liabilities (in thousands) as of March 31, 2024:


	Operating leases		Finance leases
2024 (remaining nine months)	$	17,349	$	863
2025	17,960		1,060
2026	14,089		896
2027	10,497		46
2028	8,255		46
Thereafter	21,687		144
Total lease payments	$	89,837	$	3,055
Less: Interest	16,540		371
Less: Other operating expenses	1,632		—
Total	$	71,665	$	2,684

Accounts Receivable (Tables)

3 Months Ended

Mar. 31, 2024

Receivables [Abstract]

Schedule of Accounts Receivable and Allowance for Credit Losses

Accounts receivable (in thousands) consisted of the following:


	March 31, 2024		December 31, 2023
Trade receivables	$	192,998	$	190,189
Less: Allowance for credit losses	(4,324)		(5,323)
Net trade receivables	188,674		184,866
Other receivables	832		1,051
Total accounts receivable	$	189,506	$	185,917

The following table reflects the change of the allowance for credit losses (in thousands):


	Oil & Gas Proppants		Industrial & Specialty Products		Total
Beginning balance, December 31, 2023	$	3,823	$	1,500	$	5,323
Allowance for credit losses	(700)		(328)		(1,028)
Recoveries	47		—		47
Write-offs	(18)		—		(18)
Ending balance, March 31, 2024	$	3,152	$	1,172	$	4,324

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 855,527	$ 704,694
Other comprehensive income (loss) before reclassifications	3,251
Amounts reclassified from accumulated other comprehensive income	(503)
Ending Balance	870,325	741,557
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(125)	(1,723)
Ending Balance	2,623	(2,448)
Unrealized (loss) gain on natural gas swaps
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(1,460)	(2,342)
Other comprehensive income (loss) before reclassifications	84	(969)
Amounts reclassified from accumulated other comprehensive income	0
Ending Balance	(1,376)	$ (3,311)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(981)
Other comprehensive income (loss) before reclassifications	(144)
Amounts reclassified from accumulated other comprehensive income	0
Ending Balance	(1,125)
Pension and other post-retirement benefits liability
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	2,316
Other comprehensive income (loss) before reclassifications	3,311
Amounts reclassified from accumulated other comprehensive income	(503)
Ending Balance	$ 5,124

- Definition

Amount of equity (deficit) attributable to parent and noncontrolling interest. Excludes temporary equity.

+ References

+ Details

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current Assets:
Cash and cash equivalents	$ 234,481	$ 245,716
Accounts receivable, net	189,506	185,917
Inventories, net	139,535	149,429
Prepaid expenses and other current assets	15,124	19,682
Total current assets	578,646	600,744
Property, plant and mine development, net	1,107,352	1,125,220
Lease right-of-use assets	41,678	41,095
Goodwill	185,649	185,649
Intangible assets, net	129,033	131,384
Other assets	12,701	12,501
Total assets	2,055,059	2,096,593
Current Liabilities:
Accounts payable and accrued expenses	122,588	147,479
Current portion of operating lease liabilities	17,753	18,569
Current portion of long-term debt	12,708	16,367
Current portion of deferred revenue	1,226	3,124
Income tax payable	5,697	311
Total current liabilities	159,972	185,850
Long-term debt, net	796,755	823,670
Deferred revenue	12,456	12,388
Liability for pension and other post-retirement benefits	24,679	28,715
Deferred income taxes, net	100,452	100,458
Operating lease liabilities	53,912	55,089
Other long-term liabilities	36,508	34,896
Total liabilities	1,184,734	1,241,066
Commitments and Contingencies (Note N)
Stockholders’ Equity:
Preferred stock, $0.01 par value, 10,000,000 shares authorized; zero issued and outstanding at March 31, 2024 and December 31, 2023	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized; 89,403,532 issued and 78,090,519 outstanding at March 31, 2024; 87,970,110 issued and 77,192,239 outstanding at December 31, 2023	891	877
Additional paid-in capital	1,253,497	1,249,460
Retained deficit	(190,471)	(204,159)
Treasury stock, at cost, 11,313,013 and 10,777,871 shares at March 31, 2024 and December 31, 2023, respectively	(202,363)	(196,745)
Accumulated other comprehensive income (loss)	2,623	(125)
Total U.S. Silica Holdings, Inc. stockholders’ equity	864,177	849,308
Non-controlling interest	6,148	6,219
Total stockholders' equity	870,325	855,527
Total liabilities and stockholders’ equity	$ 2,055,059	$ 2,096,593