Pension Plans - Foreign Defined Benefit Pension Plans (Details) - Foreign Pension Plans - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 8,340	$ 8,170
Interest cost	1,007	904
Expected return on plan assets	(1,128)	(947)
Amortization of prior service cost	31	9
Recognized actuarial loss	22	24
Net periodic pension cost	$ 8,272	$ 8,160