S000001470 [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 |
|
| BATS: Mortgage Total Return Series | BATS: Mortgage Total Return Series | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 8.66% | 2.13% | 5.52% | (11.88%) | (0.75%) | 5.01% | 7.13% | 1.11% | 2.61% | 2.21% |