Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 95,060	$ 101,346	$ 119,722	$ 107,095	$ 80,469	$ 91,515	$ 104,882	$ 104,653	$ 423,223	$ 381,519	$ 311,623
Other comprehensive (loss) income:
Foreign currency translation									(69,817)	(51,979)	14,056
Net change in unrecognized gains/losses on derivative instruments, net of tax									2,469	2,195	4,495
Unrealized gain on pension plan, net of tax									2,103	(10,452)	701
Total other comprehensive (loss) income									(65,245)	(60,236)	19,252
Total comprehensive income									$ 357,978	$ 321,283	$ 330,875