Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 36,433	$ 44,987
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	4,371	2,068
Interest rate swaps – net change in deferred loss	(2,568)	(7,133)
Pension – net change in deferred actuarial loss	48	37
Other comprehensive income (loss), net of tax	1,851	(5,028)
Comprehensive income	$ 38,284	$ 39,959