| Label | Element | Value | ||
|---|---|---|---|---|
| Small Cap Stock Index Portfolio | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk/Return [Heading] | oef_RiskReturnHeading | Fund Summary | ||
| Objective [Heading] | oef_ObjectiveHeading | Investment Objective | ||
| Objective, Primary [Text Block] | oef_ObjectivePrimaryTextBlock | The fund seeks to match the performance of the Standard & Poor's® SmallCap 600 Index (S&P SmallCap 600 Index). |
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| Expense Heading [Optional Text] | oef_ExpenseHeading | Fees and Expenses | ||
| Expense Narrative [Text Block] | oef_ExpenseNarrativeTextBlock | This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and examples below. These figures also do not reflect any fees or charges imposed by participating insurance companies under their Variable Annuity contracts (VA contracts) or Variable Life Insurance policies (VLI policies), and, if such fees and/or charges were included, the fees and expenses would be higher. |
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| Operating Expenses Caption [Optional Text] | oef_OperatingExpensesCaption | Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) | ||
| Portfolio Turnover [Heading] | oef_PortfolioTurnoverHeading | Portfolio Turnover | ||
| Portfolio Turnover [Text Block] | oef_PortfolioTurnoverTextBlock | The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 60.63% of the average value of its portfolio. |
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| Portfolio Turnover, Rate | oef_PortfolioTurnoverRate | 60.63% | ||
| Expense Example [Heading] | oef_ExpenseExampleHeading | Example | ||
| Expense Example Narrative [Text Block] | oef_ExpenseExampleNarrativeTextBlock | The Example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the fund for the time periods indicated and then hold or redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the fund's operating expenses remain the same. The Example does not reflect fees and expenses incurred under VA contracts and VLI policies; if they were reflected, the figures in the Example would be higher. Although your actual costs may be higher or lower, based on these assumptions your costs would be: |
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| Strategy [Heading] | oef_StrategyHeading | Principal Investment Strategy | ||
| Strategy Narrative [Text Block] | oef_StrategyNarrativeTextBlock | To pursue its goal, the fund generally is fully invested in all of the stocks that comprise the S&P SmallCap 600 Index. The fund generally invests in all of the stocks in the index in proportion to their weighting in the index; however, at times, the fund may invest in a representative sample of stocks included in the index and in futures whose performance is tied to the index. Under these circumstances, the fund expects to invest in approximately 500 or more of the stocks in the index. Because the fund has expenses, performance will tend to be slightly lower than that of the S&P SmallCap 600 Index. The fund attempts to have a correlation between its performance and that of the S&P SmallCap 600 Index of at least .95, before fees and expenses. A correlation of 1.00 would mean that the fund and the index were perfectly correlated. The S&P SmallCap 600 Index is an unmanaged index of the common stocks of 600 small-sized companies in the U.S. Standard & Poor's weights each company's stock in the index by its market capitalization (i.e., the share price times the number of shares outstanding), adjusted by the number of available float shares (i.e., those shares available to public investors). As of February 2026, companies eligible to be included in the S&P SmallCap 600 Index generally have market capitalizations ranging between approximately $1.2 billion and $8.0 billion. The fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the index is concentrated. In addition, to the extent the fund purchases securities comprising the SmallCap 600® Index, the fund may, from time to time, invest a significant portion of its assets in securities of companies in certain sectors. "Standard & Poor's®," "S&P®" and "S&P SmallCap 600® Index" are trademarks of Standard & Poor's Financial Services LLC and have been licensed for use by the fund. The fund is not sponsored, endorsed, sold or promoted by Standard & Poor's and Standard & Poor's makes no representation regarding the advisability of investing in the fund. |
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| Bar Chart and Performance Table [Heading] | oef_BarChartAndPerformanceTableHeading | Performance | ||
| Performance Narrative [Text Block] | oef_PerformanceNarrativeTextBlock | The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the performance of the fund's Service shares from year to year. The table compares the average annual total returns of the fund's shares to those of the S&P SmallCap 600® Index, an index reflecting the market segments in which the fund invests, and the S&P 1500® Index, a broad measure of market performance. The fund's past performance is not necessarily an indication of how the fund will perform in the future. More recent performance information may be available at www.bny.com/investments. |
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| Performance Additional Market Index [Text] | oef_PerformanceAdditionalMarketIndex | The table compares the average annual total returns of the fund's shares to those of the S&P SmallCap 600® Index, an index reflecting the market segments in which the fund invests, and the S&P 1500® Index, a broad measure of market performance. | ||
| Performance Availability Website Address [Text] | oef_PerformanceAvailabilityWebSiteAddress | www.bny.com/investments | ||
| Performance Past Does Not Indicate Future [Text] | oef_PerformancePastDoesNotIndicateFuture | The fund's past performance is not necessarily an indication of how the fund will perform in the future. | ||
| Bar Chart [Heading] | oef_BarChartHeading | Year-by-Year Total Returns as of 12/31 each year (%) | ||
| Bar Chart Does Not Reflect Sales Loads [Text] | oef_BarChartDoesNotReflectSalesLoads | Performance information reflects the fund's expenses only and does not reflect the fees and charges imposed by participating insurance companies under their VA contracts or VLI policies. | ||
| Bar Chart Closing [Text Block] | oef_BarChartClosingTextBlock | During the periods shown in the chart: |
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| Index No Deduction for Fees, Expenses, or Taxes [Text] | oef_IndexNoDeductionForFeesExpensesTaxes | reflects no deductions for fees, expenses or taxes | ||
| Average Annual Return, Caption [Optional Text] | oef_AverageAnnualReturnCaption | Average Annual Total Returns (as of 12/31/25) | ||
| Small Cap Stock Index Portfolio | Principal Risks | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | Principal
Risks An investment in the fund is not a bank deposit. It is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. It is not a complete investment program. The fund's share price fluctuates, sometimes dramatically, which means you could lose money. |
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| Small Cap Stock Index Portfolio | Risk Lose Money [Member] | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | The fund's share price fluctuates, sometimes dramatically, which means you could lose money. | ||
| Small Cap Stock Index Portfolio | Risk Not Insured [Member] | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | An investment in the fund is not a bank deposit. It is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. | ||
| Small Cap Stock Index Portfolio | · Market risk | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | · Market risk: The value of the securities in which the fund invests may be affected by political, regulatory, economic and social developments, and developments that impact specific economic sectors, industries or segments of the market. In addition, turbulence in financial markets and reduced liquidity in equity, credit and/or fixed-income markets may negatively affect many issuers, which could adversely affect the fund. Global economies and financial markets are becoming increasingly interconnected, and conditions and events in one country, region or financial market may adversely impact issuers in a different country, region or financial market. These risks may be magnified if certain events or developments adversely interrupt the global supply chain; in these and other circumstances, such risks might affect companies world-wide. Local, regional or global events such as war, military conflicts, acts of terrorism, natural disasters, the spread of infectious illness or other public health issues, recessions, elevated levels of government debt, changes in trade regulation or economic sanctions, internal unrest and discord, or other events could have a significant impact on the fund and its investments. |
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| Small Cap Stock Index Portfolio | · Risks of stock investing | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | · Risks of stock investing: Stocks generally fluctuate more in value than bonds and may decline significantly over short time periods. There is the chance that stock prices overall will decline because stock markets tend to move in cycles, with periods of rising prices and falling prices. The market value of a stock may decline due to general market conditions or because of factors that affect the particular company or the company's industry. |
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| Small Cap Stock Index Portfolio | · Indexing strategy risk | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | · Indexing strategy risk: The fund uses an indexing strategy. It does not attempt to manage market volatility, use defensive strategies or reduce the effects of any long-term periods of poor index performance. The correlation between fund and index performance may be affected by the fund's expenses and/or use of sampling techniques, changes in securities markets, changes in the composition of the index and the timing of purchases and redemptions of fund shares. |
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| Small Cap Stock Index Portfolio | · Small and midsize company risk | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | · Small and midsize company risk: Small and midsize companies carry additional risks because the operating histories of these companies tend to be more limited, their earnings and revenues less predictable (and some companies may be experiencing significant losses), and their share prices more volatile than those of larger, more established companies. These companies may have limited product lines, markets or financial resources, or may depend on a limited management group. Investments may be made in anticipation of future products, services or events whose delay or cancellation could cause the stock price to drop. The shares of smaller companies tend to trade less frequently than those of larger, more established companies, which can adversely affect the pricing of these securities and the fund's ability to sell these securities. |
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| Small Cap Stock Index Portfolio | · Liquidity risk | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | · Liquidity risk: When there is little or no active trading market for specific types of securities, it can become more difficult to sell the securities in a timely manner at or near their perceived value. In such a market, the value of such securities and the fund's share price may fall dramatically. Investments that are illiquid or that trade in lower volumes may be more difficult to value. Investments in foreign securities tend to have greater exposure to liquidity risk than domestic securities. |
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| Small Cap Stock Index Portfolio | · Concentration risk | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Risk [Text Block] | oef_RiskTextBlock | · Concentration risk: The fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the index is concentrated. To the extent the fund concentrates in a particular industry or group of industries or sector, it may be more susceptible to economic conditions and risks affecting those industries or sectors. |
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| Small Cap Stock Index Portfolio | S&P 1500® Index reflects no deductions for fees, expenses or taxes | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Average Annual Return, Label [Optional Text] | oef_AverageAnnualReturnLabel | S&P 1500® Index | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 17.02% | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 13.96% | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 14.46% | ||
| Small Cap Stock Index Portfolio | S&P SmallCap 600® Index reflects no deductions for fees, expenses or taxes | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Average Annual Return, Label [Optional Text] | oef_AverageAnnualReturnLabel | S&P SmallCap 600® Index | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 6.02% | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 7.31% | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 9.81% | ||
| Small Cap Stock Index Portfolio | Service Shares | ||||
| Risk/Return: | oef_RiskReturnAbstract | |||
| Management Fees (as a percentage of Assets) | oef_ManagementFeesOverAssets | 0.35% | ||
| Distribution and Service (12b-1) Fees | oef_DistributionAndService12b1FeesOverAssets | 0.25% | ||
| Other Expenses (as a percentage of Assets): | oef_OtherExpensesOverAssets | 0.01% | ||
| Expenses (as a percentage of Assets) | oef_ExpensesOverAssets | 0.61% | ||
| Fee Waiver or Reimbursement | oef_FeeWaiverOrReimbursementOverAssets | (0.00%) | [1] | |
| Net Expenses (as a percentage of Assets) | oef_NetExpensesOverAssets | 0.61% | ||
| Expense Example, with Redemption, 1 Year | oef_ExpenseExampleYear01 | $ 62 | ||
| Expense Example, with Redemption, 3 Years | oef_ExpenseExampleYear03 | 195 | ||
| Expense Example, with Redemption, 5 Years | oef_ExpenseExampleYear05 | 340 | ||
| Expense Example, with Redemption, 10 Years | oef_ExpenseExampleYear10 | $ 762 | ||
| Highest Quarterly Return, Label [Optional Text] | oef_HighestQuarterlyReturnLabel | Best Quarter | ||
| Highest Quarterly Return, Date | oef_BarChartHighestQuarterlyReturnDate | Dec. 31, 2020 | ||
| Highest Quarterly Return | oef_BarChartHighestQuarterlyReturn | 31.18% | ||
| Lowest Quarterly Return, Label [Optional Text] | oef_LowestQuarterlyReturnLabel | Worst Quarter | ||
| Lowest Quarterly Return, Date | oef_BarChartLowestQuarterlyReturnDate | Mar. 31, 2020 | ||
| Lowest Quarterly Return | oef_BarChartLowestQuarterlyReturn | (32.72%) | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 5.36% | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 6.65% | ||
| Average Annual Return, Percent | oef_AvgAnnlRtrPct | 9.15% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 25.73% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 12.40% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | (8.98%) | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 22.21% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 10.64% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 26.14% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | (16.65%) | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 15.39% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 7.96% | ||
| Annual Return [Percent] | oef_AnnlRtrPct | 5.36% | ||
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