Schedule of Restructuring, Acquisition and Divestiture Related Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost And Reserve [Line Items]
Total restructuring charges	$ 346	$ 2,970	$ 5,840
Acquisition and related charges	7,196	4,975	1,301
Divestiture related charges			1,113
Total acquisition and divestiture related charges	7,196	4,975	2,414
Total restructuring, acquisition and divestiture related costs	7,542	7,945	8,254
2016 Restructuring
Restructuring Cost And Reserve [Line Items]
Total restructuring charges	332	3,049	3,148
2015 Restructuring
Restructuring Cost And Reserve [Line Items]
Total restructuring charges			1,484
2011 Restructuring
Restructuring Cost And Reserve [Line Items]
Total restructuring charges	$ 14	$ (79)	$ 1,208