Stockholder's Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	5,992,019	5,109,062
Warrants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance		116,350
Montrose 2013 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	2,047,269	2,047,269
Montrose 2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	3,944,750	2,945,443