Income Taxes Components of current and deferred income tax expense (benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current provision (benefit)
Federal									$ 9,464	$ 8,760	$ 5,619
State and other									(13,104)	1,474	(13,968)
Current Income Tax Expense (Benefit)									(3,640)	10,234	(8,349)
Deferred provision (benefit)
Federal									312,288	277,895	232,969
State and other									22,499	33,804	(9,200)
Deferred Income Tax Expense (Benefit)									334,787	311,699	223,769
Income tax expense (benefit)	$ 140,549	$ 83,865	$ 71,820	$ 34,913	$ 145,288	$ 71,507	$ 64,303	$ 40,834	331,147	$ 321,933	215,420
Valuation allowance adjustment									$ 44,200		$ 215,420