Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details 2) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets
Property and equipment	$ 59,207	$ 0
Loss and tax credit carryforwards - state	55,979	52,917
Accrued liabilities and other reserves	15,632	29,788
Derivative contracts	13,090	0
Lease liabilities	6,354	10,841
Business interest expense carryforward	0	24,513
Business credit carryforwards	0	71,555
Unrecognized gain and original issue discount on debt exchange	0	41,556
Other	4,092	15,664
Valuation allowances	(129,408)	(77,215)
Total deferred tax assets	24,946	169,619
Deferred tax liabilities
CO2 and other contracts	(20,030)	0
Operating lease right-of-use assets	(6,190)	(7,780)
Property and equipment	0	(569,254)
Derivative contracts	0	(1,120)
Other	0	(1,695)
Total deferred tax liabilities	(26,220)	(579,849)
Total net deferred tax liability	$ (1,274)	$ (410,230)