Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Inventory reserves	$ 2,887	$ 1,428
Capitalized research costs	0	22
Capitalized inventory costs	3,156	1,541
Net operating losses	2,644	2,810
Acquired tangible assets	71	1,204
Accrued liabilities	4,070	1,090
Income tax credits	11,800	10,020
Operating lease obligations	7,878
Stock-based compensation	4,018	3,181
Amortization of intangible assets	2,169	1,135
Total deferred tax assets	38,693	22,431
Deferred tax liabilities:
Depreciation	426	661
Allowance for doubtful accounts	(270)	(739)
Right of use assets	(7,480)
Other	(3,866)	(4,189)
Total deferred tax liabilities	(11,190)	(4,267)
Net deferred tax assets before valuation allowance	27,503	18,164
Less: Valuation allowance	(24,797)	(17,261)
Net deferred tax assets	$ 2,706	$ 903