CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 34,724	$ 35,043
Adjustments to reconcile net income to net cash provided by operating activities
Provision for doubtful accounts	0	21
Depreciation, depletion, and amortization	3,975	3,999
Debt issuance costs amortization	0	16
(Gain) loss on derivative contracts	1,064	0
Cash (paid) received on settlement of derivative contracts	(1,085)	0
(Gain) loss on sale of assets	0	(19,713)
Stock-based compensation	356	235
Other	38	35
Changes in operating assets and liabilities	(6,879)	(5,305)
Net cash provided by (used in) operating activities	32,193	14,331
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures for property, plant and equipment	(5,629)	(3,094)
Purchase of other property and equipment	(49)	(59)
Proceeds from sale of assets	59	37,238
Net cash provided by (used in) investing activities	(5,619)	34,085
CASH FLOWS FROM FINANCING ACTIVITIES
Reduction of financing lease liability	(113)	(74)
Debt issuance costs	0	(74)
Proceeds from exercise of stock options	28	0
Cash paid for tax obligations on vested stock awards	(235)	(19)
Net cash provided by (used in) financing activities	(320)	(167)
NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS and RESTRICTED CASH	26,254	48,249
CASH, CASH EQUIVALENTS and RESTRICTED CASH, beginning of year	139,524	28,266
CASH, CASH EQUIVALENTS and RESTRICTED CASH, end of period	165,778	76,515
Supplemental Disclosure of Cash Flow Information
Cash paid for interest, net of amounts capitalized	(145)	(92)
Supplemental Disclosure of Noncash Investing and Financing Activities
Purchase of Plant Property and Equipment in accounts payable	680	1,342
Right-of-use assets obtained in exchange for financing lease obligations	$ 0	$ 363