Income Taxes Components of current and deferred income tax expense (benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current provision (benefit)
Federal									$ 196,186	$ (44,462)	$ 81,101
State and other									21,252	7,202	(11,801)
Current Income Tax Expense (Benefit)									217,438	(37,260)	69,300
Deferred provision (benefit)
Federal									74,700	271,544	444,695
State and other									30,738	91,233	(22,388)
Deferred Income Tax Expense (Benefit)									105,438	362,777	422,307
Income tax expense (benefit)	$ 100,153	$ 93,042	$ 79,735	$ 49,946	$ 91,842	$ 95,153	$ 85,081	$ 53,440	$ 322,876	$ 325,517	$ 491,607