Stockholder's Equity - Schedule of Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	9 Months Ended
		Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, Shares	[1]		90,116	25,289
Montrose 2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, Shares		90,384	343,971	0
Awards granted, Average Price per Share			$ 14	$ 16
Montrose 2017 Stock Incentive Plan | Restricted stock units awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, Shares		90,384	731,666	106,324
Awards forfeited, Shares		(5,343)	(8,902)
Awards vested, Shares			90,116	25,289
Awards granted, Average Price per Share		$ 38.49	$ 34.47	$ 46.82
Awards forfeited, Average Price per Share		$ 32.19	32.18
Awards vested, Average Price per Share			$ 36.81	$ 30.98
Awards granted, Fair Value		$ 3,479	$ 25,219	$ 4,978
Awards forfeited, Fair Value		$ 172	286
Awards vested, Fair Value			$ 3,317	$ 783

[1] Represents the non-cash release of common shares due to the vesting of restricted stock.