Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 166,398	$ 24,586	$ 231,011
Other comprehensive income, net of tax:
Foreign currency translation adjustments	10,723	(5,559)	(118,705)
Pension-related adjustments	(195)	3,258	1,532
Other comprehensive income	10,528	(2,301)	(117,173)
Comprehensive Income	$ 176,926	$ 22,285	$ 113,838