Core Bond Class [Member] Performance Management - Core Bond Class - AB Core Bond Portfolio |
Sep. 30, 2025 |
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| Prospectus [Line Items] | |||||||
| Bar Chart and Performance Table [Heading] | BAR CHART AND PERFORMANCE INFORMATION: | ||||||
| Performance Narrative [Text Block] |
The bar chart and performance information provide an indication of the historical risk of an investment in the Portfolio by showing:
You may obtain updated performance information for the Portfolio at www.bernstein.com (at the bottom of the page, click on “Investments,” then “Mutual Fund Performance at a Glance”).
The Portfolio’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future.
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| Performance Past Does Not Indicate Future [Text] | The Portfolio’s past performance before and after taxes, of course, does not necessarily indicate how it will perform in the future. | ||||||
| Performance Information Illustrates Variability of Returns [Text] | how the Portfolio’s performance changed from year to year over ten years; andhow the Portfolio’s average annual returns for one, five and ten years compare to those of a broad-based securities market index. | ||||||
| Bar Chart Narrative [Text Block] |
The annual returns in the bar chart are for the Core Bond Class shares.
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| Bar Chart [Heading] | Bar Chart | ||||||
| Bar Chart Closing [Text Block] | Calendar Year End (%) During the period shown in the bar chart, the Portfolio’s: Best Quarter was up 7.01%, 4th quarter, 2023; and Worst Quarter was down -6.35%, 1st quarter, 2022. | ||||||
| Performance Table Heading | Performance Table Average Annual Total Returns (For the periods ended December 31, 2025) | ||||||
| Performance Table Narrative |
After-tax returns are an estimate, which is based on the highest historical individual federal marginal income-tax rates, and do not reflect the impact of state and local taxes; actual after-tax returns depend on an individual investor’s tax situation and are likely to differ from those shown, and are not relevant to investors who hold Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.
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| Performance Table Uses Highest Federal Rate | After-tax returns are an estimate, which is based on the highest historical individual 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 individual investor’s tax situation and are likely to differ from those shown, and are not relevant to investors who hold Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. | ||||||
| Performance Availability Website Address [Text] | www.bernstein.com | ||||||
| Core Bond Class | |||||||
| Prospectus [Line Items] | |||||||
| Highest Quarterly Return, Label [Optional Text] | Best Quarter | ||||||
| Highest Quarterly Return | 7.01% | ||||||
| Highest Quarterly Return, Date | Dec. 31, 2023 | ||||||
| Lowest Quarterly Return, Label [Optional Text] | Worst Quarter | ||||||
| Lowest Quarterly Return | (6.35%) | ||||||
| Lowest Quarterly Return, Date | Mar. 31, 2022 |