Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Stock compensation expense	$ 1,867	$ 1,814
Goodwill	1,927	2,366
Royalty accruals	484	443
Bad debt allowance	345	360
Inter-company interest expense accrual	0	496
Net operating loss carryforwards	6,654	5,253
Credit carry-forwards	685	694
Inventory reserve	277	254
Depreciation	515	555
Other	539	362
Total deferred tax assets	13,293	12,597
Deferred tax liabilities:
Intangible assets	(283)	(386)
Other	(137)	(146)
Total deferred tax liabilities	(420)	(532)
Net deferred tax asset before valuation allowance	12,873	12,065
Valuation allowances for deferred tax assets	(13,044)	(12,234)	$ (13,179)	$ (7,832)
Net deferred tax asset	$ (171)	$ (169)