CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Total revenues	$ 163,701	$ 397,613	$ 390,421	$ 775,903
Costs and expenses:
Cost of sales (exclusive of items shown separately below)	130,777	205,188	282,291	387,816
Cost of other revenues (exclusive of items shown separately below)	7,642	8,019	15,203	15,764
Depreciation and depletion	22,156	25,678	50,848	47,911
Selling, general and administrative	8,457	10,783	16,913	19,688
Total costs and expenses	169,032	249,668	365,255	471,179
Operating income (loss)	(5,331)	147,945	25,166	304,724
Interest expense, net	(8,255)	(6,951)	(15,788)	(15,543)
Loss on early extinguishment of debt	0	0	0	(9,756)
Other income	0	17,543	1,822	17,543
Income (loss) before income tax expense	(13,586)	158,537	11,200	296,968
Income tax expense (benefit)	(4,425)	33,056	(1,184)	61,040
Net income (loss)	$ (9,161)	$ 125,481	$ 12,384	$ 235,928
Basic and diluted net income (loss) per share:
Net income per share—basic (in dollars per share)	$ (0.18)	$ 2.43	$ 0.24	$ 4.58
Net income per share—diluted (in dollars per share)	$ (0.18)	$ 2.43	$ 0.24	$ 4.57
Weighted average number of shares outstanding—basic (in shares)	51,187	51,553	51,147	51,532
Weighted average number of shares outstanding—diluted (in shares)	51,288	51,681	51,255	51,641
Dividends per share (in dollars per share)	$ 0.05	$ 4.46	$ 0.10	$ 4.51
Sales
Revenues:
Total revenues	$ 159,043	$ 387,429	$ 380,381	$ 757,110
Other revenues
Revenues:
Total revenues	$ 4,658	$ 10,184	$ 10,040	$ 18,793