Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
Accumulated Other Comprehensive Loss
Stockholders' equity	$ 122,119	$ 154,496	$ 140,020	[1]
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Loss
Stockholders' equity	(22,191)	(17,767)	$ (25,289)
Pension and post-retirement benefit plan adjustment
Accumulated Other Comprehensive Loss
Stockholders' equity	(3,839)	(3,367)
Unrealized gain on interest rate swap contracts
Accumulated Other Comprehensive Loss
Stockholders' equity	675	222
Foreign currency translation adjustments
Accumulated Other Comprehensive Loss
Stockholders' equity	$ (19,027)	$ (14,622)

[1] The balances as of January 1, 2017 and the year ended December 31, 2017 amounts have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 6 to the Consolidated Financial Statements.