Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized benefit—beginning of year	$ 1,791	$ 1,235	$ 0
Gross increases—current year tax positions	1,326	556	337
Gross increases—prior year tax positions	0	0	898
Decreases—prior year tax positions	0	0	0
Unrecognized benefit—end of year	$ 3,117	$ 1,791	$ 1,235