Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) - Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Issue price	$ 0.001	$ 0.001
Series B
Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Shares issued (in shares)			12,931,034
Issue price			$ 1.16
Gross proceeds			$ 15.0
Transaction Fee			$ 0.3
Convertible Preferred Stock | Series B
Redeemable Convertible Preferred Stock and Stockholders’ Deficit
Shares issued (in shares)	12,527,956	3,607,069	6,951,175
Issue price	$ 1.16	$ 1.16
Gross proceeds	$ 14.5	$ 4.2
Transaction Fee	$ 0.2	$ 0.2