Stockholder's Equity - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Exercise of options, Shares	(28,111)	(354,918)	(62,293)	(779,068)
Montrose Amended & Restated 2017 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options to Purchase Common Stock Outstanding Beginning Balance			2,036,729	1,840,229	1,840,229
Options to Purchase Common Stock Granted			664,784	264,470
Options to Purchase Common Stock Forfeited/cancelled			(60,167)	(29,025)
Options to Purchase Common Stock Expired				(1,250)
Exercise of options, Shares			(26,258)	(66,875)
Options to Purchase Common Stock Outstanding Ending Balance	2,615,088	2,007,549	2,615,088	2,007,549	2,036,729	1,840,229
Options to Purchase Common Stock Exercisable	1,010,302		1,010,302
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price per Share Outstanding Beginning Balance			$ 26	$ 23	$ 23
Weighted-Average Exercise Price per Share Granted			44	40
Weighted-Average Exercise Price per Share Forfeited/cancelled			36	28
Weighted-Average Exercise Price per Share Expired				18
Weighted-Average Exercise Price per Share Exercised			22	22
Weighted-Average Exercise Price per Share Outstanding Ending Balance	$ 30	$ 25	30	25	26	$ 23
Weighted-Average Exercise Price per Share Exercisable	26		26
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value per Share Outstanding Beginning Balance			14	12	12
Weighted Average Grant Date Fair Value per Share Granted			16	22
Weighted Average Grant Date Fair Value per Share Ending Balance	$ 15	$ 14	$ 15	$ 14	$ 14	$ 12
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contract Life (in Years) Outstanding			8 years 14 days	8 years 6 months 10 days	8 years 3 months 18 days	9 years 1 month 2 days
Weighted Average Remaining Contract Life (in Years) Exercisable			7 years 5 months 23 days
Aggregate Intrinsic Value of In-The-Money Options Outstanding	$ 18,784	$ 73,724	$ 18,784	$ 73,724	$ 91,030	$ 15,598
Aggregate Intrinsic Value of In-The-Money Options Exercised			671	$ 2,078
Aggregate Intrinsic Value of In-The-Money Options Exercisable	$ 9,966		$ 9,966
Montrose Amended and Restated 2013 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options to Purchase Common Stock Outstanding Beginning Balance			897,674	1,787,869	1,787,869
Options to Purchase Common Stock Expired			(125)	(625)
Exercise of options, Shares			(36,035)	(710,568)
Options to Purchase Common Stock Outstanding Ending Balance	861,514	1,076,676	861,514	1,076,676	897,674	1,787,869
Options to Purchase Common Stock Exercisable	861,514		861,514
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price per Share Outstanding Beginning Balance			$ 6	$ 6	$ 6
Weighted-Average Exercise Price per Share Expired			6	6
Weighted-Average Exercise Price per Share Exercised			6	6
Weighted-Average Exercise Price per Share Outstanding Ending Balance	$ 6	$ 6	6	6	6	$ 6
Weighted-Average Exercise Price per Share Exercisable	6		6
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value per Share Outstanding Beginning Balance			2	1	1
Weighted Average Grant Date Fair Value per Share Ending Balance	$ 2	$ 2	$ 2	$ 2	$ 2	$ 1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contract Life (in Years) Outstanding			3 years 7 months 9 days	4 years 7 months 24 days	4 years 4 months 13 days	5 years 4 months 24 days
Weighted Average Remaining Contract Life (in Years) Exercisable			3 years 7 months 9 days
Aggregate Intrinsic Value of In-The-Money Options Outstanding	$ 23,448	$ 59,532	$ 23,448	$ 59,532	$ 57,529	$ 43,867
Aggregate Intrinsic Value of In-The-Money Options Exercised			1,425	$ 33,480
Aggregate Intrinsic Value of In-The-Money Options Exercisable	$ 23,448		$ 23,448