Annual Total Returns - Class A |
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 |
Dec. 31, 2015 |
|---|---|---|---|---|---|---|---|---|---|---|
| MFS Core Bond Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 1.63% | 6.07% | ||||||||
| MFS Lifetime Income Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 5.97% | 9.34% | (11.76%) | 6.29% | 9.87% | 13.52% | (2.64%) | 8.05% | 5.03% | (0.68%) |
| MFS Lifetime 2025 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 6.43% | 10.14% | (12.55%) | 8.28% | 10.37% | 17.53% | (4.24%) | 13.06% | 7.28% | (0.71%) |
| MFS Lifetime 2030 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 8.13% | 12.16% | (13.99%) | 12.45% | 11.62% | 21.73% | (5.96%) | 16.91% | 8.60% | (0.72%) |
| MFS Lifetime 2035 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 10.31% | 14.55% | (15.02%) | 16.89% | 12.61% | 24.76% | (7.28%) | 19.13% | 8.87% | (0.42%) |
| MFS Lifetime 2040 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 12.06% | 16.01% | (15.48%) | 18.59% | 12.88% | 25.86% | (7.82%) | 20.47% | 8.73% | (0.13%) |
| MFS Lifetime 2045 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 12.60% | 16.32% | (15.70%) | 19.92% | 13.01% | 26.44% | (8.12%) | 20.87% | 8.81% | (0.18%) |
| MFS Lifetime 2050 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 12.92% | 16.55% | (15.87%) | 20.11% | 13.01% | 26.49% | (8.12%) | 20.86% | 8.80% | (0.14%) |
| MFS Lifetime 2055 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 12.90% | 16.51% | (15.82%) | 20.13% | 13.05% | 26.47% | (8.21%) | 20.93% | 8.74% | (0.20%) |
| MFS Lifetime 2060 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 12.99% | 16.51% | (15.97%) | 20.10% | 13.23% | 26.58% | (8.16%) | 20.92% | ||
| MFS Lifetime 2065 Fund | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 12.98% | 16.58% | (16.13%) |