Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Operations
Revenue	$ 283,394	$ 168,915	$ 230,213
Cost and expenses
Cost of sales (exclusive of items shown separately below)	195,412	145,503	162,470
Asset retirement obligations accretion	615	570	511
Depreciation and amortization	26,205	20,912	19,521
Selling, general and administrative	21,629	21,023	18,179
Total costs and expenses	243,861	188,008	200,681
Operating income (loss)	39,533	(19,093)	29,532
Other income	7,429	11,926	1,758
Interest expense, net	(2,556)	(1,224)	(1,193)
Income (loss) before tax	44,406	(8,391)	30,097
Income tax expense (benefit)	4,647	(3,484)	5,163
Net income (loss)	$ 39,759	$ (4,907)	$ 24,934
Earnings (loss) per common share
Basic earnings (in dollars per share)	$ 0.90	$ (0.12)	$ 0.61
Diluted earnings (in dollars per share)	$ 0.90	$ (0.12)	$ 0.61
Weighted average common shares outstanding
Basic weighted average shares outstanding (in shares)	43,964	42,460	40,838
Diluted weighted average shares outstanding (in shares)	44,257	42,460	40,838