Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income	$ 82,313	$ 116,042	$ 39,759
Adjustments to reconcile net income to net cash from operating activities:
Accretion of asset retirement obligations	1,403	1,115	615
Depreciation, depletion, and amortization	54,252	41,194	26,205
Amortization of debt issuance costs	776	491	214
Stock-based compensation	12,905	8,222	5,260
Loss on disposal of equipment		756
Other income - gain on insurance recoveries	(10,192)
Other income - gain on sale of mineral rights		(2,113)
Other income - employee retention tax credit			(5,407)
Deferred income taxes	18,714	29,229	4,644
Changes in operating assets and liabilities:
Accounts receivable	(55,692)	3,279	(24,154)
Prepaid expenses and other current assets	14,361	(14,378)	5,519
Inventories	7,810	(29,182)	(3,844)
Other assets and liabilities	(430)	1,127	1,124
Accounts payable	24,549	12,727	(1,820)
Accrued liabilities	10,267	19,361	5,225
Net cash provided by operating activities	161,036	187,870	53,340
Cash flows from investing activities:
Capital expenditures	(82,904)	(123,012)	(29,466)
Proceeds from sale of mineral rights		2,000
Insurance proceeds related to property, plant, and equipment	11,256
Capitalized interest	(1,137)	(1,061)
Net cash used for investing activities	(72,211)	(145,708)	(59,613)
Cash flows from financing activities:
Proceeds from borrowings	130,000	42,000	54,368
Proceeds from stock options exercised		107
Payments of debt issuance cost			(2,356)
Payment of dividends	(25,820)	(20,041)
Repayment of borrowings	(127,514)	(26,026)	(26,300)
Repayment of Ramaco Coal acquisition financing - related party	(40,000)	(15,000)
Repayments of insurance financing	(5,207)	(1,290)	(862)
Repayments of equipment finance leases	(6,659)	(5,062)	(1,942)
Shares surrendered for withholding taxes payable	(7,317)	(3,183)	(539)
Net cash (used for) provided by financing activities	(82,517)	(28,495)	22,369
Net change in cash and cash equivalents and restricted cash	6,308	13,667	16,096
Cash and cash equivalents and restricted cash, beginning of period	36,473	22,806	6,710
Cash and cash equivalents and restricted cash, end of period	42,781	36,473	22,806
Supplemental cash flow information:
Cash paid for interest (net of $1,137 and $1,061 capitalized in 2023 and 2022)	8,113	5,997	1,601
Cash paid for income taxes	771	15,500	9
Cash received for income tax refund	11,758
Non-cash investing and financing activities:
Leased assets obtained under new financing leases	6,144	7,888	10,002
Financed equipment purchases		6,409
Capital expenditures included in accounts payable and accrued liabilities	4,939	13,404	6,652
Financed insurance	5,803	5,587	280
Financed insurance (2022 adjustment recorded in 2023)	(1,136)
Accrued dividends payable	7,198	5,524	2,501
Ramaco Coal Asset Acquisition
Cash flows from investing activities:
Acquisition of assets		(11,738)
Non-cash investing and financing activities:
Coal acquisition		56,551
Maben Asset Acquisition
Cash flows from investing activities:
Acquisition of Maben assets (bond recovery in 2023)	1,182	(11,897)
Non-cash investing and financing activities:
Coal acquisition		$ 21,000
Amonate Asset Acquisition
Cash flows from investing activities:
Acquisition of assets	$ (608)		$ (30,147)