Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 29,684	$ 25,359
Inventory	874	1,442
Accruals	430	760
Depreciation and amortization	143	88
Limitation on business interest	186	96
Stock-based compensation	546	1,416
Right of use liability	776
Gross deferred tax assets	32,639	29,161
Valuation allowance	(31,840)	(29,073)
Deferred tax assets	799	88
Deferred tax liabilities:
Right of use asset	(710)
Other	(89)	(88)
Deferred tax liabilities	(799)	$ (88)
Increase in valuation allowance	$ 2,800
Tax at statutory federal rate	21.00%	21.00%