| Cover | 12 Months Ended |
| Dec. 31, 2022 | |
| Document Information [Line Items] | |
| Document Type | DEF 14A |
| Amendment Flag | false |
| Entity Information [Line Items] | |
| Entity Registrant Name | Montrose Environmental Group, Inc. |
| Entity Central Index Key | 0001643615 |
| Pay vs Performance Disclosure Unit_pure in Millions | 12 Months Ended | ||
| Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | |
| Pay vs Performance Disclosure [Table] | |||
| Pay vs Performance [Table Text Block] | Pay Versus Performance In accordance with rules adopted by the Securities and Exchange Commission pursuant to the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, we provide the following disclosure regarding executive “compensation actually paid” for our principal executive officer (“PEO”) and Non-PEO listed Year Summary (1) ($) Compensation (1),(2),(3) ($) Average Non-PEO (1) ($) Average to Non-PEO (1),(2),(3) ($) Value of Initial (4) Net Consolidated 5 ($ Millions)” TSR Peer (a) (b) (c) (d) (e) (f) (g) (h) (i) 2022 1,971,164 (33,620,506) 1,069,255 (12,569,618) 201.77 121.81 (31.8) 66.2 2021 58,421,251 78,926,873 21,580,836 30,171,824 320.50 152.66 (25.3) 73.2 2020 4,731,136 7,608,420 2,301,038 4,233,071 140.73 115.89 (57.9) 54.5 (1) Vijay Manthripragada was our PEO for each year presented. The individuals comprising the Non-PEO 2020-2022 Allan Dicks Nasym Afsari Joshua W. LeMaire Jose M. Revuelta (2) The amounts shown for Compensation Actually Paid have been calculated in accordance with Item 402(v) of Regulation S-K (3) Compensation Actually Paid reflects the exclusions and inclusions of certain amounts for the PEO and the Non-PEO Year Summary Exclusion of Stock Inclusion of Equity Compensation 2022 1,971,164 (1,062,764) (34,528,906) (33,620,506) 2021 58,421,251 (57,182,871) 77,688,493 78,926,873 2020 4,731,136 (1,438,887) 4,316,171 7,608,420 Year Average Summary Non-PEO Average Exclusion of Non-PEO Average Inclusion of Non-PEO Average Non-PEO 2022 1,069,255 (531,382) (13,107,491) (12,569,618) 2021 21,580,836 (21,019,405) 29,610,393 30,171,824 2020 2,301,038 (719,453) 2,651,486 4,233,071 The amounts in the Inclusion of Equity Values in the tables above are derived from the amounts set forth in the following tables: Year Year-End Change in Fair Vesting-Date Change in Fair Fair Value at Total - 2022 845,186 (33,528,440) 729,747 (2,575,399) 0 (34,528,906) 2021 71,029,491 6,232,690 356,047 70,265 0 77,688,493 2020 3,907,850 408,321 0 0 0 4,316,171 Year Average Year-End Awards Non- PEO NEOs Average Non-PEO Average Year for Non- PEO NEOs Average Non-PEO NEOs Average Fair Non-PEO NEOs Total - Average Non-PEO 2022 422,605 (12,595,262) 364,863 (1,299,697) 0 (13,107,491) 2021 26,235,686 3,153,597 178,024 43,086 0 29,610,393 2020 1,953,945 244,992 0 452,549 0 2,651,486 (4) The Peer Group TSR set forth in this table utilizes the MSCI USA ESG Leaders Index, which we also utilize in the stock performance graph required by Item 201(e) of Regulation S-K (5) We determined Consolidated Adjusted EBITDA to be the most important financial performance measure used to link Company performance to Compensation Actually Paid to our PEO and Non-PEO non-GAAP non-recurring | ||
| Company Selected Measure Name | Consolidated Adjusted EBITDA | ||
| Named Executive Officers, Footnote [Text Block] | 2020-2022 Allan Dicks Nasym Afsari Joshua W. LeMaire Jose M. Revuelta | ||
| Peer Group Issuers, Footnote [Text Block] | The Peer Group TSR set forth in this table utilizes the MSCI USA ESG Leaders Index, which we also utilize in the stock performance graph required by Item 201(e) of Regulation S-K | ||
| PEO Total Compensation Amount | $ 1,971,164 | $ 58,421,251 | $ 4,731,136 |
| PEO Actually Paid Compensation Amount | $ (33,620,506) | 78,926,873 | 7,608,420 |
| Adjustment To PEO Compensation, Footnote [Text Block] | Year Summary Exclusion of Stock Inclusion of Equity Compensation 2022 1,971,164 (1,062,764) (34,528,906) (33,620,506) 2021 58,421,251 (57,182,871) 77,688,493 78,926,873 2020 4,731,136 (1,438,887) 4,316,171 7,608,420 Year Year-End Change in Fair Vesting-Date Change in Fair Fair Value at Total - 2022 845,186 (33,528,440) 729,747 (2,575,399) 0 (34,528,906) 2021 71,029,491 6,232,690 356,047 70,265 0 77,688,493 2020 3,907,850 408,321 0 0 0 4,316,171 | ||
| Non-PEO NEO Average Total Compensation Amount | $ 1,069,255 | 21,580,836 | 2,301,038 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ (12,569,618) | 30,171,824 | 4,233,071 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | Year Average Summary Non-PEO Average Exclusion of Non-PEO Average Inclusion of Non-PEO Average Non-PEO 2022 1,069,255 (531,382) (13,107,491) (12,569,618) 2021 21,580,836 (21,019,405) 29,610,393 30,171,824 2020 2,301,038 (719,453) 2,651,486 4,233,071 Year Average Year-End Awards Non- PEO NEOs Average Non-PEO Average Year for Non- PEO NEOs Average Non-PEO NEOs Average Fair Non-PEO NEOs Total - Average Non-PEO 2022 422,605 (12,595,262) 364,863 (1,299,697) 0 (13,107,491) 2021 26,235,686 3,153,597 178,024 43,086 0 29,610,393 2020 1,953,945 244,992 0 452,549 0 2,651,486 | ||
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | Description of Relationship Between PEO and Non-PEO NEO Compensation Actually Paid and Company Total Shareholder Return (“TSR”) The following chart sets forth the relationship between Compensation Actually Paid to our PEO, the average of Compensation Actually Paid to our Non-PEO NEOs, and the Company’s cumulative TSR from July 23, 2020, the first day of trading of our common stock on the NYSE, over the three most recently completed fiscal years. * Performance reflected in comparable table included in our Annual Report on Form 10-K was computed based on an assumed initial investment of $100.00 at the initial public offering price per share in our initial public offering rather than the closing price on that day. | ||
| Compensation Actually Paid vs. Net Income [Text Block] | Description of Relationship Between PEO and Non-PEO NEO Compensation Actually Paid and Net Income The following chart sets forth the relationship between Compensation Actually Paid to our PEO, the average of Compensation Actually Paid to our Non-PEO NEOs, and our net income during the three most recently completed fiscal years. | ||
| Compensation Actually Paid vs. Company Selected Measure [Text Block] | Description of Relationship Between PEO and Non-PEO NEO Compensation Actually Paid and Company-Selected Measure The following chart sets forth the relationship between Compensation Actually Paid sation A | ||
| Total Shareholder Return Vs Peer Group [Text Block] | Description of Relationship Between Company TSR and Peer Group TSR The following chart compares our cumulative TSR from July 23, 2020, the first day of trading Montrose Environmental Group, Inc. TSR* MSCI USA ESG Leaders Index TSR * Performance reflected in comparable Information presented in our Annual Report on Form 10-K was computed based on an assumed initial investment of $100.00 at the initial public offering price per share in our initial public offering rather than the closing price on that day. | ||
| Tabular List [Table Text Block] | The following table presents the financial performance measures that the Company considers to have been the most important in linking Compensation Actually Paid to our PEO and other NEOs for 2022 to Company performance. The measures in this table are not ranked. Consolidated Adjusted EBITDA Acquired Adjusted EBITDA | ||
| Total Shareholder Return Amount | $ 201.77 | 320.5 | 140.73 |
| Peer Group Total Shareholder Return Amount | 121.81 | 152.66 | 115.89 |
| Net Income (Loss) | $ (31,800,000) | $ (25,300,000) | $ (57,900,000) |
| Company Selected Measure Amount | 66.2 | 73.2 | 54.5 |
| PEO Name | Vijay Manthripragada | ||
| Measure [Axis]: 1 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Consolidated Adjusted EBITDA | ||
| Non-GAAP Measure Description [Text Block] | Adjusted EBITDA is a non-GAAP non-recurring | ||
| Measure [Axis]: 2 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Acquired Adjusted EBITDA | ||
| PEO [Member] | Exclusion of Stock Awards and Option Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ (1,062,764) | $ (57,182,871) | $ (1,438,887) |
| PEO [Member] | Inclusion of Equity Values [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (34,528,906) | 77,688,493 | 4,316,171 |
| PEO [Member] | Year End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 845,186 | 71,029,491 | 3,907,850 |
| PEO [Member] | Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards Granted in Prior Years [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (33,528,440) | 6,232,690 | 408,321 |
| PEO [Member] | Vesting Date Fair Value of Equity Awards Granted During Year that Vested During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 729,747 | 356,047 | 0 |
| PEO [Member] | Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards Granted in Prior Years that Vested During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (2,575,399) | 70,265 | 0 |
| PEO [Member] | Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 0 | 0 | 0 |
| PEO [Member] | Total Inclusion of Equity Values [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (34,528,906) | 77,688,493 | 4,316,171 |
| Non-PEO NEO [Member] | Exclusion of Stock Awards and Option Awards [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (531,382) | (21,019,405) | (719,453) |
| Non-PEO NEO [Member] | Inclusion of Equity Values [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (13,107,491) | 29,610,393 | 2,651,486 |
| Non-PEO NEO [Member] | Year End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 422,605 | 26,235,686 | 1,953,945 |
| Non-PEO NEO [Member] | Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards Granted in Prior Years [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (12,595,262) | 3,153,597 | 244,992 |
| Non-PEO NEO [Member] | Vesting Date Fair Value of Equity Awards Granted During Year that Vested During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 364,863 | 178,024 | 0 |
| Non-PEO NEO [Member] | Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards Granted in Prior Years that Vested During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | (1,299,697) | 43,086 | 452,549 |
| Non-PEO NEO [Member] | Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | 0 | 0 | 0 |
| Non-PEO NEO [Member] | Total Inclusion of Equity Values [Member] | |||
| Pay vs Performance Disclosure [Table] | |||
| Adjustment to Compensation Amount | $ (13,107,491) | $ 29,610,393 | $ 2,651,486 |
