Income Taxes - Deferred Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryforward	$ 243	$ 0
Stock based compensation	10,647	7,934
Research and development and other tax credit carryforwards	0	3,251
Inventories	1,539	1,767
Employee-related expenses	51	732
Prepaid R&D expenses	620	761
Intangible assets	662	0
Deferred Tax Assets, Property, Plant and Equipment	925	0
Other	1,017	64
Total deferred tax assets	15,704	14,509
Deferred tax liabilities
Intangible assets	0	280
Prepaid expenses	43	34
Fixed assets	203	282
Deferred Tax Liabilities, Leasing Arrangements	838	0
Other	0	91
Total deferred tax liabilities	1,084	687
Valuation allowance	(951)	0
Net deferred tax assets	$ 13,669	$ 13,822