Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accounts receivable reserves	$ 738	$ 611
Accrued liabilities	1,825	1,953
Deferred compensation obligation	5,545	5,423
Stock-based compensation	723	598
Pension and post-retirement benefit plans	3,471	3,767
Goodwill and intangible assets	0	526
Foreign tax credit	1,630	1,632
Other	344	289
Deferred tax assets	14,276	14,799
Deferred tax liabilities:
Prepaid expenses	(190)	(251)
Fixed assets	(1,277)	(1,482)
Goodwill and intangible assets	(1,057)	0
Other	(254)	(17)
Deferred tax liabilities	(2,778)	(1,750)
Valuation allowance	(1,747)	(1,733)
Deferred tax assets, net	$ 9,751	$ 11,316