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, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowance, beginning of year	$ (22,797)	$ (13,546)	$ (9,738)
Increases recorded to income tax provision	(14,485)	(9,251)	(3,808)
Acquisition of business	(36,128)	0	0
Valuation allowance, end of year	$ (73,410)	$ (22,797)	$ (13,546)