Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income tax provision at statutory rate	$ 22,494	$ 16,375	$ 51,000	$ 37,245
Percentage depletion allowance	(6,347)	(5,964)	(14,111)	(13,059)
State taxes, net of effect of federal taxes	1,825	4,528	3,668	5,865
Change in valuation allowance	(19,120)	(44,278)	(42,925)	(62,234)
Current expense associated with uncertain tax positions	1,495	511	2,932	(599)
Impact of Tax Cuts and Jobs Act of 2017	0	(19,780)	0	(19,780)
Other, net	0	3,393	(56)	3,437
Provision for (benefit from) income taxes	$ 347	(45,215)	$ 508	$ (49,125)
Unrecognized tax benefit, change during period		$ 24,900

Amount of reported income tax expense (benefit) in excess of (less than) expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to Tax Cuts and Jobs Act.

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