Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets (liabilities):
Accrued expenses	$ 141	$ 83
Deferred revenue	417	522
Stock-based compensation	396	671
Fixed assets	329	320
Goodwill	167	236
Inventory	47
Inventory		(61)
Intangible amortization	(2,285)	(3,287)
R&D credit	2,154	2,700
Texas margin tax temporary credit	159	186
Other	285	125
Total deferred tax asset, net	30,542	34,410
Valuation allowance	(30,542)	(34,410)
Net deferred tax liability	0	0
Federal
Deferred tax assets (liabilities):
Tax benefit of operating loss carry forward	23,184	22,793
State
Deferred tax assets (liabilities):
Tax benefit of operating loss carry forward	$ 5,548	$ 10,122