S000001125 [Member] Annual Total Returns |
12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| AMG River Road Mid Cap Value Fund | CLASS N SHARES | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 11.75% | 13.56% | 22.64% | (8.30%) | 31.98% | 3.87% | 15.46% | (18.58%) | 11.52% | 24.06% |