Income Taxes (Components of Income Tax Expense) (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 income tax expense (benefit):
Federal									$ 107,393	$ 63,035	$ 120,968
State									86,578	64,917	72,837
Foreign									(2,485)	3,513	1,815
Total current income tax expense									191,486	131,465	195,620
Deferred income tax (benefit) expense:
Federal									(8,801)	(11,870)	40,057
State									(16,390)	(4,600)	(6,201)
Foreign									3,587	0	0
Total deferred income tax (benefit) expense									(21,604)	(16,470)	33,856
Income tax expense	$ 31,067	$ 34,951	$ 72,797	$ 31,067	$ 32,037	$ 33,563	$ 24,643	$ 24,752	$ 169,882	$ 114,995	$ 229,476