S000079761 [Member] Performance Management - AMG GW&K Municipal Enhanced SMA Shares |
Dec. 31, 2025 |
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| Prospectus [Line Items] | |
| Bar Chart and Performance Table [Heading] | Performance |
| Performance Narrative [Text Block] | The following performance information illustrates the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s performance compares to that of (i) a broad-based index and (ii) an additional index reflecting the market segment(s) in which the Fund invests. As always, past performance of the Fund (before and after taxes) is not an indication of how the Fund will perform in the future. To obtain updated performance information please visit wealth.amg.com or call 800.548.4539. The Fund is only offered to participants in certain managed account programs, and the Fund’s performance will differ from the performance of a client’s overall managed account. For more information about your managed account’s performance, contact the Subadviser or your Program Sponsor.
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| Performance Past Does Not Indicate Future [Text] | As always, past performance of the Fund (before and after taxes) is not an indication of how the Fund will perform in the future. |
| Performance Information Illustrates Variability of Returns [Text] | The following performance information illustrates the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s performance compares to that of (i) a broad-based index and (ii) an additional index reflecting the market segment(s) in which the Fund invests. |
| Bar Chart [Heading] | Calendar Year Total Returns as of 12/31/25 |
| Bar Chart Closing [Text Block] | Best Quarter: 3.71% (3rd Quarter 2025)
Worst Quarter: -1.70% (2nd Quarter 2025) |
| Performance Table Heading | Average Annual Total Returns as of 12/31/25 |
| Performance Table Narrative | After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).
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| Performance Table Uses Highest Federal Rate | After-tax returns are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state and local taxes. |
| Performance Table Not Relevant to Tax Deferred | Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”). |
| Performance Availability Website Address [Text] | wealth.amg.com |
| Performance Availability Phone [Text] | 800.548.4539 |
| AMG GW&K Municipal Enhanced SMA Shares | |
| Prospectus [Line Items] | |
| Highest Quarterly Return, Label [Optional Text] | Best Quarter: |
| Highest Quarterly Return | 3.71% |
| Highest Quarterly Return, Date | Sep. 30, 2025 |
| Lowest Quarterly Return, Label [Optional Text] | Worst Quarter: |
| Lowest Quarterly Return | (1.70%) |
| Lowest Quarterly Return, Date | Jun. 30, 2025 |