Income Taxes Components of current and deferred income tax expense (benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current provision (benefit)
Federal									$ 159,677	$ 196,186	$ (44,462)
State and other									24,580	21,252	7,202
Current Income Tax Expense (Benefit)									184,257	217,438	(37,260)
Deferred provision (benefit)
Federal									116,484	74,700	271,544
State and other									21,114	30,738	91,233
Deferred Income Tax Expense (Benefit)									137,598	105,438	362,777
Income tax expense (benefit)	$ 85,639	$ 67,769	$ 108,389	$ 60,058	$ 100,153	$ 93,042	$ 79,735	$ 49,946	$ 321,855	$ 322,876	$ 325,517