Accumulated Other Comprehensive Income (Schedule of Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provision for income taxes	$ 117,788	$ 99,792	$ 81,006
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(197)	2,251
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	27	3,200	19,836
Provision for income taxes	224	949	5,853
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(197)	2,251	13,983
Interest Rate Swaps [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		(421)	(1,042)
Foreign Currency Exchange Contracts [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	$ 27	$ 3,621	$ 20,878