Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Reserve and accruals	$ 1,704	$ 1,031
Net operating loss carryforwards	26,932	25,380
Deferred rent		242
Operating lease liability	1,448
Deferred revenue	13,173	3,525
Tax credits	9,569	4,976
Stock based compensation	1,049	314
Total gross deferred tax assets	53,875	35,468
Valuation allowance	(52,260)	(34,970)
Total deferred tax assets	1,615	498
Operating lease right-of-use asset	(1,214)
Fixed and intangible assets	(401)	(498)
Total deferred tax liabilities	$ (1,615)	$ (498)