Employee Benefits - Components of Net Periodic Benefit Cost Related to U.S Pension Benefits (Details) - Pension Plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
U.S Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 799	$ 771	$ 2,399	$ 2,518
Interest cost	1,832	1,828	5,494	5,514
Expected return on plan assets	(2,351)	(2,344)	(7,052)	(7,011)
Amortization of prior service cost	905	648	2,715	2,048
Net periodic benefit cost	1,185	903	3,556	3,069
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	695	566	1,998	1,642
Interest cost	718	632	2,093	2,264
Expected return on plan assets	(811)	(698)	(2,371)	(2,593)
Amortization of prior service cost	55	5	160	17
Net periodic benefit cost	$ 657	$ 505	$ 1,880	$ 1,330