Income Taxes (Income Tax Expense (Benefit)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current income taxes:
Current income taxes: U.S. federal	$ 327,697	$ 247,917	$ 117,602
Current income taxes: State and local	17,811	31,939	11,175
Current income taxes: Foreign	73,248	61,712	31,981
Total current income taxes	418,756	341,568	160,758
Deferred income taxes:
Deferred income taxes: U.S. federal	(17,419)	(16,167)	4,165
Deferred income taxes: State and local	(3,046)	(22,115)	(3,983)
Deferred income taxes: Foreign	(55,126)	4,273	(29,065)
Total deferred income taxes	(75,591)	(34,009)	(28,883)
Income tax expense (benefit)	$ 343,165	$ 307,559	$ 131,875