Income Taxes - Summary of Reconciliation of Company's Effective Tax Rate to Federal Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (18,984)	$ (16,094)	$ (32,464)
State income tax, net of federal tax benefit	(4,468)	(4,102)	(6,764)
Foreign tax rate differential	10,009	(2,651)	626
Stock-based compensation	(3,429)	1,885	2,378
Research and development credits	(3,066)	(2,033)	(5,247)
Other	492	805	(106)
Change in valuation allowance	20,625	19,411	41,725
Total provision for (benefit from) income taxes	$ 1,179	$ (2,779)	$ 148