Income Taxes - Deferred Tax Valuation Allowance (Details) - SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowance, beginning of year	$ (73,410)	$ (22,797)	$ (13,546)
Increases recorded to income tax provision	(18,787)	(14,485)	(9,251)
Acquisition of business	0	(36,128)	0
Valuation allowance, end of year	$ (92,197)	$ (73,410)	$ (22,797)