Stock-Based Compensation - Stock options (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended		12 Months Ended	50 Months Ended
	May 03, 2019	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Jun. 30, 2023
2015 Plan
Number of Shares
Outstanding at the beginning (in shares)		5,262,179
Granted (in shares)		2,059,250
Exercised (in shares)		(5,057)
Forfeitures (in shares)		(403,024)
Outstanding at the end (in shares)		6,913,348		5,262,179
Exercisable at the end (in shares)		3,720,545
Weighted Average Exercise Price
Outstanding at the beginning (in dollars per share)		$ 11.44
Granted (in dollars per share)		1.55
Exercised (in dollars per share)		0.99
Forfeited (in dollars per share)		5.23
Outstanding at the end (in dollars per share)		8.86		$ 11.44
Exercisable at the end (in dollars per share)		$ 12.43
Weighted Average Remaining Contractual Life (Years) And Aggregate Intrinsic Value
Outstanding (in years)		7 years 6 months		7 years 7 months 6 days
Exercisable at the end (in years)		6 years 3 months 18 days
Outstanding at the beginning (in dollars)		$ 115
Outstanding at the end (in dollars)		79		$ 115
Exercisable at the end (in dollars)		$ 79
Weighted average grant date fair value per share of stock options granted		$ 1.12
Aggregate grant date fair value		$ 7,200	$ 9,000
Share Based Compensation Expense Not Recognized
Unrecognized compensation cost		$ 9,700
Compensation expense recognition period		1 year 10 months 24 days
Omnibus Incentive Plan
Stock Based Compensation
Total number of shares of common stock that may be issued		2,900,000
Annual increase in number of share reserved for issuance (as percent)	4.00%
2015 Plan and 2019 Employee Stock Purchase Plan
Stock Based Compensation
Vesting period		4 years
Expiration period		10 years
Number of shares reserved for issuance under the plan		2,108,622
2019 Employee Stock Purchase Plan
Stock Based Compensation
Number of shares issued					109,958
Number of shares reserved for issuance under the plan		680,722