Debt and Financing Arrangements (Details) $ in Thousands						3 Months Ended	9 Months Ended
	Feb. 08, 2024 USD ($)	Aug. 03, 2022 USD ($)	Jul. 29, 2021 USD ($) M	Nov. 03, 2020 USD ($)	Jul. 02, 2020 USD ($)	Mar. 31, 2024 shares	Sep. 30, 2024 USD ($) shares	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Aug. 02, 2022 USD ($)	Mar. 04, 2021 USD ($)
Debt Instrument [Line Items]
Receipt of shares from the exercise of capped call | shares						315,721	315,721
Restricted cash							$ 1,100	$ 1,100	$ 1,100
Debt financing costs	$ 1,500						1,516
Outstanding debt							126,897		$ 140,595
New Term Loan Debt Facility | Secured Debt
Debt Instrument [Line Items]
Term loan, face value	20,000
Amortization payments	$ 3,300
Term loan due 2025
Debt Instrument [Line Items]
Term loan, face value							13,300
Total net leverage	2.00
Term of financial maintenance covenants, maximum total net leverage ratio	12 months
Maximum consolidated EBITDA to consolidated interest expense ratio	3.50
Term of financial maintenance covenants on consolidated EBITDA	12 months
Customary mandatory prepayment events	100.00%
Payments on term loan							6,666
Proceeds from issuance of debt							20,000
Term loan due 2025 | Minimum
Debt Instrument [Line Items]
Financial maintenance covenant for liquidity	$ 100,000
Term loan due 2025 | SOFR
Debt Instrument [Line Items]
Applicable margin on interest rate	3.00%
Adjustment to basis spread on variable rate	0.10%
Floor, basis spread on variable rate	0.00%
Term loan due 2025 | Base Rate
Debt Instrument [Line Items]
Applicable margin on interest rate	2.00%
Term loan due 2024
Debt Instrument [Line Items]
Payments on term loan	$ 3,500						3,502	2,250
Accounts Receivable Securitization Facility | Line of Credit | Secured Debt
Debt Instrument [Line Items]
Current borrowing capacity							79,600
Letters of credit outstanding							50,500
Accounts Receivable Securitization Facility | Regions Bank | Line of Credit | Secured Debt
Debt Instrument [Line Items]
Current borrowing capacity		$ 150,000								$ 110,000
Inventory-Based Revolving Credit Facility
Debt Instrument [Line Items]
Covenant amount							23,800
Inventory-Based Revolving Credit Facility | Regions Bank | Line of Credit | Secured Debt
Debt Instrument [Line Items]
Term loan, face value		$ 50,000
Letters of credit outstanding							26,200
Borrowing base percentage, coal inventory		85
Borrowing base percentage, parts and supplies inventory		85
Borrowing base, percentage of clause		35
Percent of eligible cash		100.00%
Covenant amount		$ 100,000
Equipment financing arrangement | Secured Debt
Debt Instrument [Line Items]
Term loan, face value			$ 23,500
Number of monthly payments | M			42
Interest rate			7.35%
Tax Exempt Bonds
Debt Instrument [Line Items]
Term loan, face value							$ 98,100
Series 2020 Tax Exempt Bonds
Debt Instrument [Line Items]
Term loan, face value					$ 53,100
Interest rate					5.00%
Mandatory tender percentage					100.00%
Series 2021 Tax Exempt Bonds
Debt Instrument [Line Items]
Term loan, face value											$ 45,000
Interest rate											4.125%
Convertible Notes
Debt Instrument [Line Items]
Term loan, face value				$ 155,300
Interest rate				5.25%
Net proceeds of convertible debt				$ 132,700
Principal amount of convertible notes								13,200
Cash on convertible notes								58,400
Deferred Offering Costs				5,100
Loss on debt conversion								$ 1,100
Capped Call Transactions
Debt Instrument [Line Items]
Capped call, transaction cost				$ 17,500