Income Taxes Reconciliation of Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory tax benefit	$ 136,873	$ (120,335)	$ (420,671)
Federal tax reform changes - 2017 Tax Act	0	(63,675)	0
State tax benefit (net of federal benefit)	2,771	(3,286)	(17,549)
Change in valuation allowance	105	(2,727)	(5,059)
Employee share based compensation	2,508	8,190	0
Other	1,113	(1,137)	(893)
Total income tax expense (benefit)	$ 143,370	$ (182,970)	$ (444,172)