Stockholders' Equity - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Unrecognized pension and postretirement benefit costs, net of tax	$ 34	$ 34
Foreign currency translation losses, net of tax	(5,716)	(2,703)
Total accumulated other comprehensive loss	$ (5,682)	$ (2,669)