Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ 146,479	$ 133,251	$ 282,832	$ 335,888
Pension and post-retirement benefit plan adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(3,367)	(4,439)
Unrealized gain (loss) on interest rate swap contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	222	(204)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	(14,622)	(20,646)
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' equity	$ (17,767)	$ (25,289)	$ (17,940)	$ (11,892)