Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	90,000,000	50,000,000
Common stock, shares issued	388,415	256,548
Common stock, shares outstanding	388,415	256,548
Series B-2 Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	44,453,477	0
Redeemable convertible preferred stock, shares issued	44,453,477	0
Redeemable convertible preferred stock, shares outstanding	44,453,477	0
Redeemable convertible preferred stock, liquidation preference	$ 127,090	$ 127,090
Series B Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	31,989,428	20,942,781
Redeemable convertible preferred stock, shares issued	20,942,781	20,942,781
Redeemable convertible preferred stock, shares outstanding	20,942,781	20,942,781
Redeemable convertible preferred stock, liquidation preference	$ 55,300	$ 55,300
Series A-1 and A-2 Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	6,167,726	6,167,726
Redeemable convertible preferred stock, shares issued	6,167,726	6,167,726
Redeemable convertible preferred stock, shares outstanding	6,167,726	6,167,726
Redeemable convertible preferred stock, liquidation preference	$ 7,114	$ 7,114