American Funds Balanced Allocation Portfolio Investment Strategy - American Funds Balanced Allocation Portfolio	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#000000;font-family:Times New Roman;font-size:11.5pt;font-weight:bold;">Principal Investment Strategies</span>
Strategy Narrative [Text Block]	The Portfolio will invest substantially all of its assets in shares of the Underlying Portfolios, which are funds of the American Funds Insurance Series® and other funds within the American Fund family that are not part of the American Funds Insurance Series. The Portfolio has a target allocation between the broad asset classes of equity and fixed income. Brighthouse Investment Advisers, LLC (“BIA”), the adviser to the Portfolio, establishes specific target investment percentages for the broad asset classes and the various components of each asset category. BIA determines these target allocations based on a variety of models and factors, including its long-term outlook for the return and risk characteristics of the various asset classes and the relationship between those asset classes. BIA then selects the Underlying Portfolios in which the Portfolio invests based on, among other factors, the Underlying Portfolios’ investment objectives, policies, investment process and portfolio analytical and management personnel. Under normal circumstances, the Portfolio primarily invests in Underlying Portfolios that may hold large cap, small cap, mid cap or foreign equity securities and also invests in Underlying Portfolios that hold fixed income securities in accordance with target allocations of 65% to equity securities and 35% to fixed income securities. The following chart describes the target allocations, as of April 27, 2026, between equity and fixed income securities. You should note that these percentages do not directly correspond to investment in the Underlying Portfolios because each Underlying Portfolio may contain one or more asset classes (e.g., equity and fixed income) and each Underlying Portfolio may contain various subsets of an asset class (e.g., small cap, mid cap and foreign securities). Although the Portfolio’s investments in the Underlying Portfolios will be made in an attempt to achieve the target allocations, the actual allocations to equity and fixed income securities may vary from the Portfolio’s target allocations in the chart below. Deviations from the asset class target allocations will affect the asset class subset target allocations. In addition, the Portfolio’s actual allocations could vary substantially from the target allocations due to market valuation changes.Asset ClassTarget AllocationEquity65%Domestic Equity43.5%Foreign Equity21.5%Fixed Income35%U.S. Investment Grade27.5%U.S. High Yield4%Foreign Fixed Income3.5%Individual figures may not add up to the totals shown due to rounding. The “Foreign Equity” allocation shown above may be invested in foreign equity securities of any capitalization or country but primarily will be invested in larger capitalization companies of developed countries, and the “Foreign Fixed Income” allocation shown above may be invested in foreign fixed securities of any credit quality but primarily will be invested in investment grade debt. The Portfolio seeks to achieve capital growth through its investments in Underlying Portfolios that invest in equity securities. These investments may include Underlying Portfolios that invest mainly in stocks of large established U.S. companies as well, to a lesser extent, in stocks of foreign companies and smaller U.S. companies with above-average growth potential. The Portfolio seeks to achieve current income through its investments in Underlying Portfolios that invest in fixed income securities. These investments may include Underlying Portfolios that invest exclusively in bonds of U.S. issuers. The Portfolio may invest in Underlying Portfolios that invest in U.S. and foreign investment-grade securities, as well as Underlying Portfolios that invest in high-yield, high-risk bonds (commonly known as “junk bonds”). Periodically, BIA will evaluate the Portfolio’s allocation between equity and fixed income, inclusive of the exposure to various investment styles and asset sectors, relative to the Portfolio’s risk profile. It is anticipated that any changes to the targets for the broad asset classes will be, in any given year, within a range of plus or minus 10% from the current allocations. Concurrently, BIA will consider whether to make changes to the Portfolio’s investments in any of the Underlying Portfolios. For additional information about the Portfolio’s investment strategies, the names of the Underlying Portfolios in which the Portfolio may invest and where to find more detailed information about the Portfolio’s investments in the Underlying Portfolios, please see “Additional Information about the Portfolio’s Investment Strategies” in the Prospectus.

American Funds Balanced Allocation Portfolio Investment Strategy - American Funds Balanced Allocation Portfolio

Dec. 31, 2025

<span style="color:#000000;font-family:Times New Roman;font-size:11.5pt;font-weight:bold;">Principal Investment Strategies</span>

Strategy Narrative [Text Block]

The Portfolio will invest substantially all of its assets in shares of the Underlying Portfolios, which are funds of the American Funds Insurance Series® and other funds within the American Fund family that are not part of the American Funds Insurance Series. The Portfolio has a target allocation between the broad asset classes of equity and fixed income. Brighthouse Investment Advisers, LLC (“BIA”), the adviser to the Portfolio, establishes specific target investment percentages for the broad asset classes and the various components of each asset category. BIA determines these target allocations based on a variety of models and factors, including its long-term outlook for the return and risk characteristics of the various asset classes and the relationship between those asset classes. BIA then selects the Underlying Portfolios in which the Portfolio invests based on, among other factors, the Underlying Portfolios’ investment objectives, policies, investment process and portfolio analytical and management personnel. Under normal circumstances, the Portfolio primarily invests in Underlying Portfolios that may hold large cap, small cap, mid cap or foreign equity securities and also invests in Underlying Portfolios that hold fixed income securities in accordance with target allocations of 65% to equity securities and 35% to fixed income securities. The following chart describes the target allocations, as of April 27, 2026, between equity and fixed income securities. You should note that these percentages do not directly correspond to investment in the Underlying Portfolios because each Underlying Portfolio may contain one or more asset classes (e.g., equity and fixed income) and each Underlying Portfolio may contain various subsets of an asset class (e.g., small cap, mid cap and foreign securities). Although the Portfolio’s investments in the Underlying Portfolios will be made in an attempt to achieve the target allocations, the actual allocations to equity and fixed income securities may vary from the Portfolio’s target allocations in the chart below. Deviations from the asset class target allocations will affect the asset class subset target allocations. In addition, the Portfolio’s actual allocations could vary substantially from the target allocations due to market valuation changes.Asset ClassTarget Allocation*Equity65%Domestic Equity43.5%Foreign Equity21.5%Fixed Income35%U.S. Investment Grade27.5%U.S. High Yield4%Foreign Fixed Income3.5%*Individual figures may not add up to the totals shown due to rounding. The “Foreign Equity” allocation shown above may be invested in foreign equity securities of any capitalization or country but primarily will be invested in larger capitalization companies of developed countries, and the “Foreign Fixed Income” allocation shown above may be invested in foreign fixed securities of any credit quality but primarily will be invested in investment grade debt. The Portfolio seeks to achieve capital growth through its investments in Underlying Portfolios that invest in equity securities. These investments may include Underlying Portfolios that invest mainly in stocks of large established U.S. companies as well, to a lesser extent, in stocks of foreign companies and smaller U.S. companies with above-average growth potential. The Portfolio seeks to achieve current income through its investments in Underlying Portfolios that invest in fixed income securities. These investments may include Underlying Portfolios that invest exclusively in bonds of U.S. issuers. The Portfolio may invest in Underlying Portfolios that invest in U.S. and foreign investment-grade securities, as well as Underlying Portfolios that invest in high-yield, high-risk bonds (commonly known as “junk bonds”). Periodically, BIA will evaluate the Portfolio’s allocation between equity and fixed income, inclusive of the exposure to various investment styles and asset sectors, relative to the Portfolio’s risk profile. It is anticipated that any changes to the targets for the broad asset classes will be, in any given year, within a range of plus or minus 10% from the current allocations. Concurrently, BIA will consider whether to make changes to the Portfolio’s investments in any of the Underlying Portfolios. For additional information about the Portfolio’s investment strategies, the names of the Underlying Portfolios in which the Portfolio may invest and where to find more detailed information about the Portfolio’s investments in the Underlying Portfolios, please see “Additional Information about the Portfolio’s Investment Strategies” in the Prospectus.