Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021		Jan. 31, 2023	Jan. 31, 2022	May 31, 2015
Class Of Stock [Line Items]
Common stock, shares authorized		190,000,000		190,000,000
Common stock, par value		$ 0.000004		$ 0.000004
Stock issued on exercise of warrants		67,713				67,713	[1]
Total unrecognized stock compensation expense related to unvested options, restricted stock and stock appreciation rights granted under the Plans		$ 122,800
Unrecognized expense expected to be recognized period		3 years
Shares, granted	[1]	90,815		25,532		42,263
Share based compensation expense		$ 47,267		$ 43,290		$ 10,321
Shares reserved for future issuance		9,439,847		8,580,219		8,968,866
Restricted shares outstanding		2,846,019		2,064,197		1,957,873
Supplemental Incentive Plans
Class Of Stock [Line Items]
Shares, granted		370,349		95,404		0
Montrose 2017 Stock Incentive Plan
Class Of Stock [Line Items]
Shares of vested over period						5 years
Shares, granted						1,671,391
Share based, description						These RSUs represent the right to receive one share of the Company’s common stock upon vesting. These incentives were designed to (i) retain selected employees of the Company for a minimum of 5 years, (ii) reward selected employees for the Company’s significant outperformance and stockholder value creation in 2021, and (iii) provide incentives to selected employees of the Company to accelerate value creation for stockholders and other stakeholders over the next five-year period.
Share based compensation expense						$ 90,000
Shares reserved for future issuance		8,647,656	[2]	7,724,524	[2]	6,921,597	[2]	1,189,801	1,185,112
Restricted shares forfeited				0		0
Montrose Amended and Restated 2013 Stock Option Plan
Class Of Stock [Line Items]
Shares outstanding from exercised options		1,549,788		1,310,430		1,209,090
RSUs | Supplemental Incentive Plans
Class Of Stock [Line Items]
Shares of vested over period		4 years
Shares, vested		237,634
RSUs | Supplemental Incentive Plans | On the date of grant
Class Of Stock [Line Items]
Shares, vesting rights, percentage		33.33%
RSUs | Supplemental Incentive Plans | On the one-year anniversary of the grant
Class Of Stock [Line Items]
Shares, vesting rights, percentage		33.33%
RSUs | Supplemental Incentive Plans | On the two-year anniversary of the grant
Class Of Stock [Line Items]
Shares, vesting rights, percentage		33.33%
RSUs | Montrose 2017 Stock Incentive Plan
Class Of Stock [Line Items]
Shares, granted						1,355,182
Shares, vesting rights, percentage						50.00%
Shares reserved for future issuance						135,517
Performance-Vested RSUs | Montrose 2017 Stock Incentive Plan
Class Of Stock [Line Items]
Shares, granted						316,209
Shares, vesting rights, percentage						50.00%
Stock Appreciation Rights (SARs) | Two Thousand Seventeen Plan
Class Of Stock [Line Items]
Shares of vested over period						5 years
Shares, granted						3,000,000
Share based compensation expense		$ 9,185		$ 9,280		$ 307
Exercise price						$ 66.79
Remaining contractual terms		10 years
Fair value vested in period		$ 46,000
Weighted average remaining contract life		7 years 11 months 15 days
Stock Options | Montrose 2017 Stock Incentive Plan | Board of Directors
Class Of Stock [Line Items]
Shares of vested over period		4 years
Stock Options | Montrose 2017 Stock Incentive Plan | Executive Officers
Class Of Stock [Line Items]
Shares of vested over period		3 years
Vesting frequency of period		1 year
Stock Options | Montrose 2017 Stock Incentive Plan | On the two-year anniversary of the grant | Board of Directors
Class Of Stock [Line Items]
Shares, vesting rights, percentage		50.00%
Stock Options | Montrose 2017 Stock Incentive Plan | Fourth Anniversary | Board of Directors
Class Of Stock [Line Items]
Shares, vesting rights, percentage		50.00%
Stock Options | Two Thousand Seventeen Plan
Class Of Stock [Line Items]
Share based compensation expense		$ 6,570		$ 10,038		$ 8,034
Restricted Stock | Montrose 2017 Stock Incentive Plan
Class Of Stock [Line Items]
Shares RSAs granted		17,346		10,920		19,309
Restricted Stock | Two Thousand Seventeen Plan
Class Of Stock [Line Items]
Share based compensation expense		$ 31,512		$ 23,972		$ 1,959
Private Offering
Class Of Stock [Line Items]
Warrants to purchase common stock										116,350
Warrant exercise price per share										$ 17.19

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

[2] In January 2023 and January 2022 the Board of Directors ratified the addition of 1,189,801 and 1,185,112 shares of common stock, respectively, to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. The Company expects to have sufficient shares available under the 2017 Plan to satisfy the future settlement of outstanding awards. Shares reserved for future issuance include 3,000,000 shares underlying the 3,000,000 performance SARs granted in December 2021 that are subject to vesting based on the achievement of certain market conditions. Assuming achievement at the highest price performance hurdle, approximately 2,000,000 shares of common stock would be issued upon vesting of these performance SARs. Shares available for grant exclude these awards. To date, none of the market conditions, have yet been, and they may not be, achieved.