Net Loss per Share - Summary of Basic and Diluted Net loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net loss	$ (52,807)	$ (33,285)	$ (21,994)
Accruing dividends on Series A convertible preferred stock	592	3,000	3,000
Adjustment to accumulated deficit in connection with repurchase of Series Seed convertible preferred stock	0	22	0
Net loss attributable to common stockholders	$ (53,399)	$ (36,307)	$ (24,994)
Weighted average shares of common stock outstanding - basic and diluted (in shares)	11,530	459	458
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (4.63)	$ (79.15)	$ (54.58)