Income Taxes (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 income taxes:
Federal									$ 75,154	$ 55,664	$ 44,266
State									19,194	18,270	18,349
Foreign									6,501	5,913	(872)
Total current income taxes									100,849	79,847	61,743
Deferred income taxes:
Federal									284	33,345	40,500
State									(2,834)	13,099	11,705
Foreign									(1,508)	(1,887)	3,019
Total deferred income taxes									(4,058)	44,557	55,224
Total income tax expense	$ 33,507	$ 29,969	$ 9,044	$ 24,271	$ 30,718	$ 35,480	$ 28,707	$ 29,499	$ 96,791	$ 124,404	$ 116,967