General and Basis of Presentation - Restructuring (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	$ 5,383
Restructuring expenses	2,413	$ 8,243	$ 10,400
Payments	(4,224)
Restructuring Reserve, Ending Balance	3,572		$ 5,383
Current Portion Of Other Long-Term Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Ending Balance	27
Accrued Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Ending Balance	3,169
Other Long-Term Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Ending Balance	376
North America
Restructuring Reserve [Roll Forward]
Restructuring expenses	1,057	3,727
Europe And Africa
Restructuring Reserve [Roll Forward]
Restructuring expenses	681	787
Restructuring Reserve, Ending Balance	952
Europe And Africa | Current Portion Of Other Long-Term Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Ending Balance	27
Europe And Africa | Accrued Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Ending Balance	549
Europe And Africa | Other Long-Term Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Ending Balance	376
Corporate Segment
Restructuring Reserve [Roll Forward]
Restructuring expenses	675	$ 3,729
Restructuring Reserve, Ending Balance	2,620
Corporate Segment | Accrued Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Ending Balance	$ 2,620