Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Millions				3 Months Ended		9 Months Ended		12 Months Ended
		Jul. 29, 2021 USD ($) $ / shares shares	Jul. 22, 2021	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) Subsidiary $ / shares shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares		Jun. 30, 2021 shares
Subsequent Event [Line Items]
Number of wholly owned subsidiaries | Subsidiary						2
Preferred stock, shares outstanding				0		0		14,376,272	[1]
Aggregate shares of common stock				14,725,309		14,725,309
Reverse stock split			1-for-10.33
Cash, cash equivalents, and short-term investments | $				$ 168.3		$ 168.3		$ 69.0
Losses from operations | $				$ 13.1	$ 8.9	$ 38.1	$ 27.1
Common stock, shares authorized		900,000,000		900,000,000		900,000,000
Common stock par value per share | $ / shares				$ 0.001		$ 0.001		$ 0.001
Preferred stock, shares authorized				100,000,000		100,000,000		16,572,792	[1]
Preferred stock par value per share | $ / shares				$ 0.001		$ 0.001		$ 0.001
Convertible Preferred Stock
Subsequent Event [Line Items]
Preferred stock, shares outstanding				14,376,272		14,376,272
Preferred stock, shares authorized		100,000,000
Preferred stock par value per share | $ / shares		$ 0.001		$ 0.001		$ 0.001		$ 0.001
Series H Convertible Preferred Stock
Subsequent Event [Line Items]
Sale of stock, date								Feb. 28, 2017
Common stock par or stated value per share | $ / shares								$ 12.40
Preferred stock, shares outstanding	[1]							3,805,567
Warrants exercised										225,945
Number of converted shares of common stock				100,261		100,261
Preferred stock, shares authorized	[1]							5,949,499
Preferred stock par value per share | $ / shares								$ 0.001
IPO [Member]
Subsequent Event [Line Items]
Sale of shares		7,350,000
Sale of stock, date		Jul. 29, 2021
Common stock par or stated value per share | $ / shares		$ 16.00
Additional common shares sold		898,549
Aggregate net proceeds from offering | $		$ 120.0
Common stock sale underwriting discounts and commission deducted | $		9.2
Common Stock Offering Costs | $		$ 3.2

[1] The shares authorized, issued and outstanding do not reflect any anti-dilution provisions of Series C, Series D, Series E and Series F as a result of the Series G financing.