Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020
Income Taxes
Income tax provision at statutory rate	$ (40,128)	$ 22,494	$ (55,922)	$ 51,000
Percentage depletion allowance	2,242	(6,347)	(3,358)	(14,111)
State taxes, net of effect of federal taxes	(2,695)	1,825	(4,197)	3,668
Change in valuation allowance	40,734	(19,120)	61,115	(42,925)
Current expense associated with uncertain tax positions	226	1,495	3,327	2,932
AMT sequestration refund			(1,171)
Other, net			0	(56)
Provision for (benefit from) income taxes	379	$ 347	(206)	$ 508
Refund, AMT credits					$ 37,400
Tax reserve for portion of refund subject to audit	$ 13,300		$ 13,300
Percentage of the total income tax refund amount subject to audit	40.00%

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The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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