Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 31,683	$ 29,684
Inventory	147	874
Accruals	254	430
Depreciation and amortization	240	143
Limitation on business interest	268	186
Stock-based compensation	676	546
Right of use liability	549	776
Gross deferred tax assets	33,817	32,639
Valuation allowance	(33,265)	(31,840)
Deferred tax assets	552	799
Deferred tax liabilities:
Right of use asset	(527)	(710)
Other	(25)	(89)
Deferred tax liabilities	(552)	(799)
Increase in valuation allowance	$ 1,400	$ 2,800
Tax at statutory federal rate	21.00%	21.00%