| Form N-CSR Cover | 12 Months Ended |
| Sep. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BERNSTEIN SANFORD C FUND II INC |
| Entity Central Index Key | 0001166729 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Sep. 30, 2024 |
| Shareholder Report | 12 Months Ended |
| Sep. 30, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | BERNSTEIN SANFORD C FUND II INC |
| Entity Central Index Key | 0001166729 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Sep. 30, 2024 |
| C000030507 | |
| Shareholder Report [Line Items] | |
| Fund Name | Intermediate Duration Institutional Portfolio |
| Class Name | Intermediate Duration Institutional Class |
| Trading Symbol | SIIDX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about the Intermediate Duration Institutional Portfolio (the “Portfolio”) for the period of October 1, 2023 to September 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information about the Fund at https://www.abfunds.com/link/BWM/SIIDX-A. You can also request this information by contacting us at (800) 227 4618. |
| Additional Information Phone Number | (800) 227 4618 |
| Additional Information Website | https://www.abfunds.com/link/BWM/SIIDX-A |
| Expenses [Text Block] | What were the Fund costs for the last year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Intermediate Duration Institutional Class $48 0.45% |
| Expenses Paid, Amount | $ 48 |
| Expense Ratio, Percent | 0.45% |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? What affected the Fund’s performance? During the 12-month period ended September 30, 2024, the Portfolio outperformed the Bloomberg US Aggregate Bond Index (net) ("the benchmark"). Security selection contributed the most to performance, relative to the benchmark, particularly selections in investment-grade corporates, US agency mortgage-backed securities, asset-backed securities and commercial mortgage-backed securities. Additionally, sector allocation was additive, mainly from off-benchmark exposure to agency risk-sharing securities and an underweight to US Treasuries, that were partially offset by losses from off-benchmark exposure to US Treasury futures and inflation-linked bonds, along with an underweight to investment-grade bonds. Yield-curve positioning from an overweight on the six-month part of the curve also contributed to performance. Country allocation was a minor detractor. During the 12-month period, derivatives were used in the form of futures and interest rate swaps were used to manage and hedge duration risk and/or to take active yield-curve positioning. Currency forwards were used to hedge foreign currency exposure, and credit default swaps were used to hedge credit risk and as a tool to effectively gain exposure to specific sectors. |
| Performance Past Does Not Indicate Future [Text] | |
| Line Graph [Table Text Block] | Intermediate Duration Institutional Class Bloomberg U.S. Aggregate Bond Index 09/14 $10,000 $10,000 09/15 $10,252 $10,294 09/16 $10,910 $10,829 09/17 $10,997 $10,836 09/18 $10,887 $10,705 09/19 $11,944 $11,807 09/20 $12,775 $12,632 09/21 $12,781 $12,518 09/22 $10,847 $10,691 09/23 $10,891 $10,760 09/24 $12,319 $12,004 |
| Average Annual Return [Table Text Block] | Average Annual Total Returns 1 Year 5 Years 10 Years Intermediate Duration Institutional Class 13.01 % 0.61 % 2.11 % Bloomberg U.S. Aggregate Bond Index 11.57 % 0.33 % 1.84 % The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or the redemption or sale of Fund shares. Visit https://www.abfunds.com/link/BWM/SIIDX-A for the most recent performance information. |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or the redemption or sale of Fund shares. |
| AssetsNet | $ 770,782,114 |
| Holdings Count | Holding | 551 |
| Advisory Fees Paid, Amount | $ 2,725,881 |
| InvestmentCompanyPortfolioTurnover | 206% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Net Assets $770,782,114 # of Portfolio Holdings 551 Portfolio Turnover Rate 206% Total Advisory Fees Paid $2,725,881 |
| Holdings [Text Block] | Portfolio Breakdown Value Value Governments - Treasuries 32.2% Corporates - Investment Grade 23.6% Mortgage Pass-Throughs 22.1% Collateralized Mortgage Obligations 6.1% Asset-Backed Securities 6.1% Commercial Mortgage-Backed Securities 2.4% Agencies 1.7% Inflation-Linked Securities 1.2% Other 4.0% Short-Term Investments 11.8% Other assets less liabilities - |
| Material Fund Change [Text Block] |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | ||||||||||
| Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2014 | |
| C000030507 | |||||||||||
| Account Value [Line Items] | |||||||||||
| Line Graph and Table Measure Name | Intermediate Duration Institutional Class | ||||||||||
| Account Value | $ 12,319 | $ 10,891 | $ 10,847 | $ 12,781 | $ 12,775 | $ 11,944 | $ 10,887 | $ 10,997 | $ 10,910 | $ 10,252 | $ 10,000 |
| AllianceBernstein Index: Bloomberge US Aggregate Bond Index | |||||||||||
| Account Value [Line Items] | |||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Aggregate Bond Index | ||||||||||
| Account Value | $ 12,004 | $ 10,760 | $ 10,691 | $ 12,518 | $ 12,632 | $ 11,807 | $ 10,705 | $ 10,836 | $ 10,829 | $ 10,294 | $ 10,000 |
| Shareholder Report, Average Annual Return (Details) | 12 Months Ended | 60 Months Ended | 120 Months Ended |
| Sep. 30, 2024 | Sep. 30, 2024 | Sep. 30, 2024 | |
| C000030507 | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Intermediate Duration Institutional Class | ||
| Without Sales Load [Member] | C000030507 | |||
| Average Annual Return [Line Items] | |||
| Average Annual Return, Percent | 13.01% | 0.61% | 2.11% |
| AllianceBernstein Index: Bloomberge US Aggregate Bond Index | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Bloomberg U.S. Aggregate Bond Index | ||
| Average Annual Return, Percent | 11.57% | 0.33% | 1.84% |
| Shareholder Report, Holdings (Details) - C000030507 | Sep. 30, 2024 |
| 10239902 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.80% |
| 10239363 | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (11.20%) |
| AssetGovernments - Treasuries | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.20% |
| AssetCorporates - Investment Grade | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.60% |
| AssetMortgage Pass-Throughs | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 22.10% |
| AssetCollateralized Mortgage Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| AssetAsset-Backed Securities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| AssetCommercial Mortgage-Backed Securities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| AssetAgencies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| AssetInflation-Linked Securities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| AssetCollateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
