Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforward, Annual limitation		$ 11,700
Unrealized Built In Gain, For Realizing Future NOLs		$ 176,900
U.S. federal income tax rate	21.00%	35.00%
Change In Valuation Allowance Due To Tax Cuts And Jobs Act	$ 0	$ 0	$ (64,949)
Refundable Alternative Minimum Tax Credits	0	0	1,402
Federal tax net operating loss carryforwards	455,800
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	456,200
Change in valuation allowance	0	(64,994)	$ 0
Deferred income taxes	$ 97,418	139,534
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Increase (Decrease) in Operating Loss Carryforward		(276,100)
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Increase (Decrease) in Operating Loss Carryforward		(14,000)
Increase (Decrease) in Tax Credit Carryforward		(8,200)
Fifth Creek
Operating Loss Carryforwards [Line Items]
Deferred income taxes		$ 137,700