Income Taxes Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 196,825	$ 159,547	$ 138,432
State	27,149	27,120	25,952
Foreign	58,123	45,545	32,931
Current income tax expense, total	282,097	232,212	197,315
Deferred:
Federal	(37,486)	1,169	22,233
State	4,044	2,131	1,212
Foreign	(13,095)	(14,946)	(1,057)
Deferred income tax expense, total	(46,537)	(11,646)	22,388
Provision for income taxes	$ 235,560	$ 220,566	$ 219,703