CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Total revenues	$ 213,764	$ 226,720
Costs and expenses:
Cost of sales (exclusive of items shown separately below)	154,350	151,514
Cost of other revenues (exclusive of items shown separately below)	7,795	7,561
Depreciation and depletion	32,903	28,692
Selling, general and administrative	7,637	8,456
Total costs and expenses	202,685	196,223
Operating income	11,079	30,497
Interest expense, net	(8,693)	(7,533)
Other income (expense)	(109)	1,822
Income before income tax expense	2,277	24,786
Income tax expense	23,632	3,241
Net (loss) income	$ (21,355)	$ 21,545
Basic and diluted net (loss) income per share:
Net (loss) income per share-basic (in dollars per share)	$ (0.42)	$ 0.42
Net (loss) income per share-diluted (in dollars per share)	$ (0.42)	$ 0.42
Weighted average number of shares outstanding-basic (in shares)	51,274	51,106
Weighted average number of shares outstanding-diluted (in shares)	51,274	51,273
Dividends per share (in dollars per share)	$ 0.05	$ 0.05
Sales
Revenues:
Total revenues	$ 206,989	$ 221,338
Other revenues
Revenues:
Total revenues	$ 6,775	$ 5,382