Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
OPERATING ACTIVITIES:
Net income (loss)	$ 7,986	$ 1,923	$ 3,990	$ (1,483)
Deferred income taxes	(1,359)	(387)	(2,691)	(2,657)
Equity income – Sunrise Energy	(90)	119	(153)	(1,167)
Cash distribution - Sunrise Energy			0	1,125
Depreciation, depletion and amortization	9,842	9,315	29,864	30,159
Asset impairment	0	1,799	0	1,799
Gain on extinguishment of debt	(10,000)	0	(10,000)	0
Loss on sale of assets			0	38
Unrealized gain on marketable securities			0	(14)
Amortization of debt issuance costs	657	610	1,908	1,686
Asset retirement obligations accretion	380	348	1,116	1,024
Stock-based compensation			834	927
Change in current assets and liabilities:
Accounts receivable			(2,041)	9,742
Inventory			13,341	(9,247)
Parts and supplies			(918)	2,603
Prepaid income taxes			0	1,562
Prepaid expenses			(4,631)	1,744
Accounts payable and accrued liabilities			8,960	(5,488)
Other			161	0
Cash provided by operating activities			37,031	34,109
INVESTING ACTIVITIES:
Investment in Sunrise Energy			0	(113)
Capital expenditures			(18,075)	(13,991)
Proceeds from sale of equipment			0	56
Proceeds from sale of marketable securities			0	2,310
Proceeds from maturities of certificates of deposit			0	245
Cash used in investing activities			(18,075)	(11,493)
FINANCING ACTIVITIES:
Payments on bank debt			(37,062)	(40,475)
Borrowings of bank debt			(14,250)	(7,250)
Proceeds from PPP loan			0	10,000
Debt issuance costs			(418)	(1,903)
Taxes paid on vesting of RSUs			(2)	(18)
Dividends paid			0	(1,236)
Cash used in financing activities			(23,232)	(26,382)
Decrease in cash, cash equivalents, and restricted cash			(4,276)	(3,766)
Cash, cash equivalents, and restricted cash, beginning of period			12,071	13,311
Cash, cash equivalents, and restricted cash, end of period	7,795	9,545	7,795	9,545
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH CONSIST OF THE FOLLOWING:
Cash and cash equivalents	4,546	5,302	4,546	5,302
Restricted cash	3,249	4,243	3,249	4,243
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending Balance	$ 7,795	$ 9,545	7,795	9,545
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest			6,728	8,246
SUPPLEMENTAL NON-CASH FLOW INFORMATION:
Change in capital expenditures included in accounts payable and prepaid expense			5,782	968
Interest Rate Swap [Member]
OPERATING ACTIVITIES:
Change in fair value of derivative			(2,330)	981
Fuel Hedge [Member]
OPERATING ACTIVITIES:
Change in fair value of derivative			$ (379)	$ 775