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Restructuring Charges - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges (Note 5)	$ (2,615)	$ (3,214)		$ (10,223)	$ (16,920)
Currency translation and other adjustments				(700)		$ (300)
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring charges (Note 5)				(4,700)
Currency translation and other adjustments				0		0
Americas
Restructuring Cost and Reserve [Line Items]
Restructuring charges (Note 5)				(2,000)	(12,500)
Currency translation and other adjustments				(300)		(200)
International
Restructuring Cost and Reserve [Line Items]
Restructuring charges (Note 5)				(3,500)	$ (4,400)
Currency translation and other adjustments				$ (400)		$ (100)
Voluntary Retirement Incentive Package \| Special Termination Benefits
Restructuring Cost and Reserve [Line Items]
Severance costs			$ 11,400