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Midcap Stock Portfolio  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Fund Summary
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund seeks investment results that are greater than the total return performance of publicly traded common stocks of medium-size domestic companies in the aggregate, as represented by the Standard & Poor's MidCap 400® Index (S&P 400 Index).
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the fund. These figures 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.
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_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 82.88% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 82.88%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_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:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

To pursue its goal, the fund normally invests at least 80% of its net assets, plus any borrowings for investment purposes, in stocks of mid-cap companies. The fund invests in growth and value stocks, which are chosen through a disciplined investment process that combines computer modeling techniques, fundamental analysis and risk management. Consistency of returns compared to the S&P 400 Index, the fund's benchmark, is a primary goal of the investment process.


The fund's portfolio managers select stocks through a "bottom-up," structured approach that seeks to identify undervalued securities using a quantitative ranking process. The process is driven by a proprietary quantitative model that measures a diverse set of corporate characteristics to identify and rank stocks based on valuation, momentum and sentiment and earnings quality measures.


Next, the fund's portfolio managers construct the portfolio through a risk controlled process, focusing on stock selection as opposed to making proactive decisions as to industry and sector exposure. The portfolio managers seek to maintain a portfolio that has exposure to industries and market capitalizations that are generally similar to the fund's benchmark. Finally, within each sector and style subset, the fund will seek to overweight the most attractive stocks and underweight or not hold the stocks that have been ranked least attractive.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

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.


· 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.


· Midsize company risk. 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.


· Growth and value stock risk. By investing in a mix of growth and value companies, the fund assumes the risks of both. Investors often expect growth companies to increase their earnings at a certain rate. If these expectations are not met, investors can punish the stocks inordinately, even if earnings do increase. In addition, growth stocks may lack the dividend yield that may cushion stock prices in market downturns. Value stocks involve the risk that they may never reach their expected full market value, either because the market fails to recognize the stock's intrinsic worth or the expected value was misgauged.


· 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.  Recent examples include pandemic risks related to COVID-19 and aggressive measures taken world-wide in response by governments, including closing borders, restricting international and domestic travel, and the imposition of prolonged quarantines of large populations, and by businesses, including changes to operations and reducing staff.  The effects of COVID-19 have contributed to increased volatility in global markets and will likely affect certain countries, companies, industries and market sectors more dramatically than others. The COVID-19 pandemic has had, and any other outbreak of an infectious disease or other serious public health concern could have, a significant negative impact on economic and market conditions and could trigger a prolonged period of global economic slowdown. To the extent the fund may overweight its investments in certain countries, companies, industries or market sectors, such positions will increase the fund's exposure to risk of loss from adverse developments affecting those countries, companies, industries or sectors.


· Management risk. The investment process used by the fund's portfolio managers could fail to achieve the fund's investment goal and cause your fund investment to lose value.

Risk Lose Money [Text] rr_RiskLoseMoney The fund's share price fluctuates, sometimes dramatically, which means you could lose money.
RIsk Not Insured [Text] rr_RiskNotInsured 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_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 Initial shares from year to year. The table compares the average annual total returns of the fund's shares to those of 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.bnymellonim.com/us.


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. Because these fees and charges will reduce total return, policyowners should consider them when evaluating and comparing the fund's performance. Policyowners should consult the prospectus for their contract or policy for more information.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.bnymellonim.com/us
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund's past performance is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Year-by-Year Total Returns as of 12/31 each year (%) Initial Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_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] rr_BarChartClosingTextBlock

Best Quarter
Q4, 2011: 14.93%

Worst Quarter
Q3, 2011: -19.71%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 14.93%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.71%)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes reflects no deductions for fees, expenses or taxes
Average Annual Return, Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (as of 12/31/19)
Midcap Stock Portfolio | S&P MidCap 400® Index reflects no deductions for fees, expenses or taxes  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 26.20%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 9.03%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.72%
Midcap Stock Portfolio | Midcap Stock Portfolio - Initial Shares  
Risk/Return: rr_RiskReturnAbstract  
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.11%
Total annual fund operating expenses rr_ExpensesOverAssets 0.86%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 88
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 274
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 477
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,061
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 88
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 274
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 477
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,061
Annual Return 2010 rr_AnnualReturn2010 27.10%
Annual Return 2011 rr_AnnualReturn2011 0.40%
Annual Return 2012 rr_AnnualReturn2012 19.67%
Annual Return 2013 rr_AnnualReturn2013 34.99%
Annual Return 2014 rr_AnnualReturn2014 12.09%
Annual Return 2015 rr_AnnualReturn2015 (2.29%)
Annual Return 2016 rr_AnnualReturn2016 15.47%
Annual Return 2017 rr_AnnualReturn2017 15.38%
Annual Return 2018 rr_AnnualReturn2018 (15.49%)
Annual Return 2019 rr_AnnualReturn2019 20.18%
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 20.18%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 5.75%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.82%
Midcap Stock Portfolio | Midcap Stock Portfolio - Service Shares  
Risk/Return: rr_RiskReturnAbstract  
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.11%
Total annual fund operating expenses rr_ExpensesOverAssets 1.11%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 113
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 353
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 612
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,352
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 113
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 353
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 612
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,352
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 19.85%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 5.48%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.55%