Income Taxes (Income Tax Provision (Benefit)) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2020	Sep. 18, 2020	Dec. 31, 2019	Dec. 31, 2018
Current income tax expense (benefit)
Federal	$ 0	$ (6,407)	$ 2,645	$ (17,885)
State	30	(853)	1,236	1,884
Total current income tax expense (benefit)	30	(7,260)	3,881	(16,001)
Deferred income tax expense (benefit)
Federal	0	(319,011)	89,950	93,395
State	(2,556)	(89,858)	10,521	9,839
Total deferred income tax expense (benefit)	(2,556)	(408,869)	100,471	103,234
Total income tax expense (benefit)	$ (2,526)	$ (416,129)	$ 104,352	$ 87,233