Income Taxes - Reconciliation of Provision for Income Taxes at Statutory Rate and Provision (Benefit) for Income Taxes at Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax at federal statutory rate	$ (6,659)	$ (3,846)	$ (3,871)
Increase/(decrease) in tax resulting from:
State income tax expense, net of federal tax effect	(421)	(183)	(103)
Nondeductible permanent items	1,506	1,012	567
Foreign rate differential	599	662	474
Tax rate change	7,226	(13)	(74)
Adjustment to deferred taxes	37	(132)	(525)
Change in valuation allowance	(2,291)	2,351	2,921
Uncertain tax positions	76	83	50
Other	(26)	42	(1)
Total	$ 47	$ (24)	$ (562)