Description of Business - Additional Information (Details) $ / shares in Units, $ in Thousands				3 Months Ended	9 Months Ended	114 Months Ended
	Sep. 22, 2020 USD ($) $ / shares shares	Sep. 16, 2020 USD ($) shares	Sep. 11, 2020	Sep. 30, 2020 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 23, 2020 shares	Jun. 30, 2020 shares	Dec. 31, 2019 shares	Sep. 30, 2019 shares	Jun. 30, 2019 shares	Dec. 31, 2018 shares
Description Of Business [Line Items]
Reverse stock split, description			On September 11, 2020, the Company effected a one-for-7.9302 reverse split of its issued and outstanding common stock, convertible preferred stock, warrants, and stock options.
Reverse stock split conversion ratio			0.1261
Net proceeds from public offering | $					$ 187,224
Loss on final re-measurement of fair value of warrant liability | $				$ 641	$ 641
Temporary equity shares outstanding				0	0	0			2,617,386
Net cash proceeds from issuance of convertible preferred stock, common stock warrants, and convertible notes | $						$ 288,500
Cash, cash equivalents, and investments | $				$ 259,900	$ 259,900	$ 259,900
Common Stock Warrants
Description Of Business [Line Items]
Common shares issued upon exercise of warrants		1,085,334
Series B Convertible Preferred Stock Warrant
Description Of Business [Line Items]
Common shares issued upon exercise of warrants		59,093
Series B Convertible Preferred Stock Warrant | Other Income (Expense), Net
Description Of Business [Line Items]
Loss on final re-measurement of fair value of warrant liability | $		$ 600
Convertible Preferred Stock, Common Stock Warrants Or Series B Convertible Preferred Stock Warrants
Description Of Business [Line Items]
Temporary equity shares outstanding							0
Convertible Preferred Stock
Description Of Business [Line Items]
Temporary equity shares outstanding								12,503,009	2,617,386	2,617,386	2,617,386	2,617,386
IPO
Description Of Business [Line Items]
Number of shares issued and sold	12,000,000
Public offering price per share | $ / shares	$ 17.00
Net proceeds from public offering | $	$ 186,400
IPO | Convertible Preferred Stock
Description Of Business [Line Items]
Common shares issued on conversion of convertible preferred stock	12,503,009