CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest [Abstract]
Net income	$ 18,520	$ 1,542
Unrealized gain on defined benefit plan, net of tax	435	856
Unrealized gain on interest rate swap, net of tax	2,348	527
Unrealized foreign currency gain, net of tax	15,855	9,442
Comprehensive income	37,158	12,367
Less: Comprehensive income attributable to noncontrolling interest	6	(325)
Total comprehensive income attributable to common stockholders	$ 37,164	$ 12,042