Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020	Dec. 31, 2019
Tax Credit Carryforward [Line Items]
Income tax expense (benefit)	$ (8,152)	$ 7,599	$ (9,336)	$ 68,639
Income tax benefit from Internal Revenue Code			3,300
Income tax benefit from depletion expense			3,200
Income tax benefit from loss recognized before income taxes			2,900
Adjustment out of income tax receivable, noncurrent	0		0			$ (11,349)
Adjustment into income tax receivable, current	0		$ 0			$ 12,925
Refunds of AMT credits	$ 24,300
Restatement Adjustment
Tax Credit Carryforward [Line Items]
Adjustment out of income tax receivable, noncurrent					$ 11,300
Adjustment into income tax receivable, current					$ 11,300