Income Taxes - Deferred Income Taxes Components (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforward	$ 66,319	$ 53,189
Property & equipment	403	648
Inventory	397	395
Stock options	13,217	11,473
Intangible assets, definite-lived	38	40
General business credit	11,306	9,300
Operating Lease Liability - ASC 842	908
Other	59	47
Total deferred income tax assets	92,647	75,092
Valuation allowance	(81,946)	(63,060)
Deferred tax assets	10,701	12,032
Deferred income tax liabilities:
Debt amortization	(9,793)	(12,032)
Right of use asset	(908)
Total deferred income tax liabilities	(10,701)	(12,032)
Net deferred income taxes	$ 0	$ 0