Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Parenthetical) (Details) - shares	Jan. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance		8,968,866	5,109,062	3,706,994
Montrose Amended and Restated 2013 Stock Option Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance		2,047,269	2,047,269	2,058,619
Montrose Amended and Restated 2013 Stock Option Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance	1,185,112,000
Stock Appreciation Rights Units Grant | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance	3,000,000,000