Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryforwards	$ 49,211	$ 31,311
Credit carryforwards	8,638	6,655
Stock-based compensation	5,142	4,073
Compensation accruals	2,297	1,873
Lease liability	18,404
Accruals and reserves	795	3,223
Gross deferred tax assets	84,487	47,135
Valuation allowance	(62,274)	(38,010)
Total deferred tax assets, net of valuation allowance	22,213	9,125
Deferred tax liabilities
Intangible assets	(605)	(734)
Prepaid expenses	(1,688)	(1,503)
Convertible senior notes	(5,359)	(6,888)
Right-of-use assets	(13,579)
Fixed assets	(982)	0
Total deferred tax liabilities	(22,213)	(9,125)
Net deferred tax assets and liabilities	$ 0	$ 0