Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ (56,675)	$ (33,422)	$ (16,939)
Foreign	36	68	20
Loss before provision for income taxes	(56,639)	(33,354)	(16,919)
Current:
U.S. Federal	0	0	0
State	20	7	2
Foreign	7	21	6
Total current	27	28	8
Deferred:
U.S. Federal	(1,064)	0	(61)
State	(332)	0	(8)
Foreign	0	0	0
Total deferred	(1,396)	0	(69)
Total provision for (benefit from) income taxes	$ (1,369)	$ 28	$ (61)