Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Accounts receivable reserves	$ 611	$ 812
Accrued liabilities	1,953	3,400
Deferred compensation obligation	5,423	9,206
Stock-based compensation	598	2,196
Pension and post-retirement benefit plans	3,767	6,029
Goodwill and intangible assets	526	3,869
Foreign tax credit	1,632	0
Other	289	230
Deferred tax assets	14,799	25,742
Deferred tax liabilities:
Prepaid expenses	(251)	(260)
Fixed assets	(1,482)	(1,593)
Other	(17)	(355)
Deferred tax liabilities	(1,750)	(2,208)
Valuation allowance	(1,733)	(85)
Deferred tax assets, net	$ 11,316	$ 23,449