CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest [Abstract]
Net income	$ 31,736	$ 18,520
Unrealized (loss) gain on defined benefit plan, net of tax	(6,029)	435
Unrealized (loss) gain on swaps and collars, net of tax	(3,909)	2,348
Unrealized foreign currency gain, net of tax	4,936	15,856
Comprehensive income	26,734	37,159
Less: Comprehensive income attributable to noncontrolling interest	(20)	6
Total comprehensive income attributable to common stockholders	$ 26,714	$ 37,165