Income Taxes - Reconciliation of the Federal Statutory Tax Provision to the Effective Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal tax benefit at statutory rate	$ (14,480)	$ (13,298)	$ (13,147)
State tax	93	(10)	2,009
Foreign rate differential	136	1,315	2,513
Non-deductible permanent items	(468)	4,129	1,142
Stock-based compensation	(9,850)	(1,178)	1,950
Tax credits	(1,403)	(922)	(1,702)
Change in valuation allowance	25,780	11,114	(14,653)
Tax Act-revaluation of deferred taxes	0	0	21,875
Total income tax provision (benefit)	$ (192)	$ 1,150	$ (13)