Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Provision for (benefit from) income taxes	$ (1,369)	$ 28	$ (61)
Valuation allowance increase (decrease)	21,000	19,000
Deferred tax liabilities	8,101	2,773	479
Change in valuation allowance			9,700
Unrecognized tax benefits	3,117	1,791	1,235	$ 0
Maximum
Operating Loss Carryforwards [Line Items]
Provision for (benefit from) income taxes		100	(100)
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	189,284	122,824	66,906
Tax credit carryforwards	6,630	3,312	2,070
Federal | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	6,600
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	90,300
Tax credit carryforwards	4,258	$ 2,273	$ 1,292
State | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 4,300