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Label Element Value
Class 2 Shares Prospectus | Ultra-Short Bond Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Ultra-Short Bond Fund
Objective [Heading] rr_ObjectiveHeading Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The investment objective of the fund is to provide current income, consistent with the maturity and quality standards applicable to the fund, and preservation of capital and liquidity.

Expense [Heading] rr_ExpenseHeading Fees and expenses of the fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy, hold and sell an interest in Class 2 shares of the fund. You may pay other fees, such as insurance contract fees and expenses, which are not reflected in the tables and examples below. If insurance contract fees and expenses were reflected, expenses shown 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 rate may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s investment results. During the most recent fiscal year, the fund’s portfolio turnover rate was either less than 1% of the average value of its portfolio or there was no turnover. However, calculation of the fund's portfolio turnover rate excludes securities whose maturities or expiration dates at the time of acquisition were one year or less.

Portfolio Turnover, Rate rr_PortfolioTurnoverRate 1.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in Class 2 shares of 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 redeem or hold 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 insurance contract expenses. If insurance contract expenses were reflected, expenses shown would be higher. No sales charge (load) or other fees are charged by the fund upon redemption, so you would incur these hypothetical costs whether or not you were to redeem your shares at the end of the given period.

Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading Principal investment strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Normally, the fund invests at least 80% of its assets in bonds and other debt securities. The fund invests substantially in short-term government securities and high-quality money market instruments, such as commercial paper, commercial bank obligations and ultra-short-term debt securities. The fund maintains a dollar-weighted average portfolio maturity of 60 days or less.

The fund may enter into repurchase agreements that are fully collateralized by cash or government securities. When it enters into a repurchase agreement, the fund purchases a security from a bank or broker-dealer and obtains a simultaneous commitment from the seller to repurchase the security at a specified time and price. Because the security purchased by the fund constitutes collateral for the seller’s repurchase obligation, a repurchase agreement is effectively a loan by the fund that is collateralized by the security purchased. The fund will only enter into repurchase agreements involving securities of the type (excluding any maturity limitations) in which it could otherwise invest.

The fund may invest in securities issued by entities domiciled outside the United States and securities with credit and liquidity support features provided by entities domiciled outside the United States. The fund may also invest in securities of U.S. issuers with substantial operations outside the United States.

The fund relies on the professional judgment of its investment adviser to make decisions about the fund’s portfolio investments. The basic investment philosophy of the investment adviser is to seek to provide current income while preserving capital and maintaining liquidity.

Risk [Heading] rr_RiskHeading Principal risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Investment results
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following bar chart shows how the investment results of the Class 2 shares of the fund have varied from year to year, and the following table shows how the fund’s average annual total returns for various periods compare with a broad measure of securities market results and other applicable measures of market results. This information provides some indication of the risks of investing in the fund. The Lipper Ultra Short Obligation Funds Average and the Lipper Money Market Funds Average include mutual funds that disclose investment objectives and/or strategies reasonably comparable to those of the fund. Past investment results (before and after taxes) are not predictive of future investment results. Figures shown reflect fees and expenses associated with an investment in the fund, but do not reflect insurance contract fees and expenses. If insurance contract fees and expenses were included, results would have been lower. The results for certain of the years shown reflect the operation of the fund as a cash management fund prior to its conversion to an ultra-short-term bond fund on May 1, 2016. Accordingly, results for such periods may not be representative of the fund's results had the fund been operated as an ultra-short-term bond fund during the entire period. Updated information on the fund’s investment results can be obtained by visiting capitalgroup.com/afis.

Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart shows how the investment results of the Class 2 shares of the fund have varied from year to year, and the following table shows how the fund’s average annual total returns for various periods compare with a broad measure of securities market results and other applicable measures of market results.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex The Lipper Ultra Short Obligation Funds Average and the Lipper Money Market Funds Average include mutual funds that disclose investment objectives and/or strategies reasonably comparable to those of the fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress capitalgroup.com/afis
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past investment results (before and after taxes) are not predictive of future investment results.
Bar Chart [Heading] rr_BarChartHeading Calendar year total returns
Bar Chart Narrative [Text Block] rr_BarChartNarrativeTextBlock

The following bar chart shows how the investment results of the Class 2 shares of the fund have varied from year to year, and the following table shows how the fund’s average annual total returns for various periods compare with a broad measure of securities market results and other applicable measures of market results.

 

Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Figures shown reflect fees and expenses associated with an investment in the fund, but do not reflect insurance contract fees and expenses. If insurance contract fees and expenses were included, results would have been lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Highest/Lowest quarterly results during this period were:

 

Highest  1.26% (quarter ended December 31, 2023)

 

Lowest  -0.18% (quarter ended December 31, 2021)

Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2023
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.26%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2021
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (0.18%)
Average Annual Return, Caption rr_AverageAnnualReturnCaption Average annual total returns For the periods ended December 31, 2023:
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Risk Not Insured [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Your investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency, entity or person.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Risk Lose Money [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock You may lose money by investing in the fund.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Market Conditions [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Market conditions — The prices of, and the income generated by, the securities held by the fund may decline – sometimes rapidly or unpredictably – due to various factors, including events or conditions affecting the general economy or particular industries or companies; overall market changes; local, regional or global political, social or economic instability; governmental, governmental agency or central bank responses to economic conditions; changes in inflation rates; and currency exchange rate, interest rate and commodity price fluctuations.Economies and financial markets throughout the world are highly interconnected. Economic, financial or political events, trading and tariff arrangements, wars, terrorism, cybersecurity events, natural disasters, public health emergencies (such as the spread of infectious disease), bank failures and other circumstances in one country or region, including actions taken by governmental or quasi-governmental authorities in response to any of the foregoing, could have impacts on global economies or markets. As a result, whether or not the fund invests in securities of issuers located in or with significant exposure to the countries affected, the value and liquidity of the fund’s investments may be negatively affected by developments in other countries and regions.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Issuer Risks [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Issuer risks — The prices of, and the income generated by, securities held by the fund may decline in response to various factors directly related to the issuers of such securities, including reduced demand for an issuer’s goods or services, poor management performance, major litigation, investigations or other controversies related to the issuer, changes in the issuer’s financial condition or credit rating, changes in government regulations affecting the issuer or its competitive environment and strategic initiatives such as mergers, acquisitions or dispositions and the market response to any such initiatives. An individual security may also be affected by factors relating to the industry or sector of the issuer or the securities markets as a whole, and conversely an industry or sector or the securities markets may be affected by a change in financial condition or other event affecting a single issuer.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Interest Rate Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Interest rate risk — The values and liquidity of the securities held by the fund may be affected by changing interest rates. For example, the values of these securities may decline when interest rates rise and increase when interest rates fall. Longer maturity debt securities generally have greater sensitivity to changes in interest rates and may be subject to greater price fluctuations than shorter maturity debt securities. The fund may invest in variable and floating rate securities. When the fund holds variable or floating rate securities, a decrease in market interest rates will adversely affect the income received from such securities and the net asset value of the fund’s shares. Although the values of such securities are generally less sensitive to interest rate changes than those of other debt securities, the value of variable and floating rate securities may decline if their interest rates do not rise as quickly, or as much, as market interest rates. Conversely, floating rate securities will not generally increase in value if interest rates decline. During periods of extremely low short-term interest rates, the fund may not be able to maintain a positive yield or total return and, in relatively low interest rate environments, there are heightened risks associated with rising interest rates.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Investing In Securities Backed By The USGovernment [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Investing in securities backed by the U.S. government — Securities backed by the U.S. Treasury or the full faith and credit of the U.S. government are guaranteed only as to the timely payment of interest and principal when held to maturity. Accordingly, the current market values for these securities will fluctuate with changes in interest rates and the credit rating of the U.S. government. Notwithstanding that these securities are backed by the full faith and credit of the U.S. government, circumstances could arise that would prevent or delay the payment of interest or principal on these securities, which could adversely affect their value and cause the fund to suffer losses. Such an event could lead to significant disruptions in U.S. and global markets. Securities issued by U.S. government-sponsored entities and federal agencies and instrumentalities that are not backed by the full faith and credit of the U.S. government are neither issued nor guaranteed by the U.S. government. U.S. government securities are subject to market risk, interest rate risk and credit risk.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Investing In Repurchase Agreements [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Investing in repurchase agreements — Upon entering into a repurchase agreement, the fund purchases a security from a bank or broker-dealer, which simultaneously commits to repurchase the security within a specified time at the fund’s cost with interest. The security purchased by the fund constitutes collateral for the seller’s repurchase obligation. If the party agreeing to repurchase should default, the fund may seek to sell the security it holds as collateral. The fund may incur a loss if the value of the collateral securing the repurchase obligation falls below the repurchase price. The fund may also incur disposition costs and encounter procedural delays in connection with liquidating the collateral.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Credit And Liquidity Support [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Credit and liquidity support — Changes in the credit quality of banks and financial institutions providing credit and liquidity support features with respect to securities held by the fund could cause the values of these securities to decline.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Investing Outside The United States [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Investing outside the United States — Securities of issuers domiciled outside the United States or with significant operations or revenues outside the United States, and securities tied economically to countries outside the United States, may lose value because of adverse political, social, economic or market developments (including social instability, regional conflicts, terrorism and war) in the countries or regions in which the issuers are domiciled, operate or generate revenue or to which the securities are tied economically. These securities may also lose value due to changes in foreign currency exchange rates against the U.S. dollar and/or currencies of other countries. Issuers of these securities may be more susceptible to actions of foreign governments, such as nationalization, currency blockage or the imposition of price controls, sanctions, or punitive taxes, each of which could adversely impact the value of these securities. Securities markets in certain countries may be more volatile and/or less liquid than those in the United States. Investments outside the United States may also be subject to different regulatory, legal, accounting, auditing, financial reporting and recordkeeping requirements, and may be more difficult to value, than those in the United States. In addition, the value of investments outside the United States may be reduced by foreign taxes, including foreign withholding taxes on interest and dividends. Further, there may be increased risks of delayed settlement of securities purchased or sold by the fund, which could impact the liquidity of the fund’s portfolio. The risks of investing outside the United States may be heightened in connection with investments in emerging markets.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Management [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock Management — The investment adviser to the fund actively manages the fund’s investments. Consequently, the fund is subject to the risk that the methods and analyses, including models, tools and data, employed by the investment adviser in this process may be flawed or incorrect and may not produce the desired results. This could cause the fund to lose value or its investment results to lag relevant benchmarks or other funds with similar objectives.
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Bloomberg Short-Term Government/Corporate Index (reflects no deduction for sales charges, account fees, expenses or U.S. federal income taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 5.19%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.98%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.41%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception [1]
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Lipper Ultra-Short Obligation Funds Average (reflects no deduction for sales charges, account fees or U.S. federal income taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 5.83%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 2.08%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.54%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 4.04% [1]
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Lipper Money Market Funds Average (reflects no deduction for sales charges, account fees or U.S. federal income taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 4.80%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.67%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.07%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 3.35% [1]
Class 2 Shares Prospectus | Ultra-Short Bond Fund | Class 2  
Risk/Return: rr_RiskReturnAbstract  
Management fee rr_ManagementFeesOverAssets 0.26%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.05%
Total annual fund operating expenses rr_ExpensesOverAssets 0.56%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 57
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 179
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 313
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 701
Annual Return 2014 rr_AnnualReturn2014 (0.54%)
Annual Return 2015 rr_AnnualReturn2015 (0.45%)
Annual Return 2016 rr_AnnualReturn2016 (0.18%)
Annual Return 2017 rr_AnnualReturn2017 0.46%
Annual Return 2018 rr_AnnualReturn2018 1.36%
Annual Return 2019 rr_AnnualReturn2019 1.62%
Annual Return 2020 rr_AnnualReturn2020 0.03%
Annual Return 2021 rr_AnnualReturn2021 (0.55%)
Annual Return 2022 rr_AnnualReturn2022 1.17%
Annual Return 2023 rr_AnnualReturn2023 4.64%
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 4.64%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 1.37%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 0.74%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 2.95% [1]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 1997
[1] Lifetime returns are from February 8, 1984, the date the fund began investment operations. Class 2 shares began investment operations on April 30, 1997; therefore, returns for the fund prior to that date assume a hypothetical investment in Class 1 shares, but reflect the .25% annual expense that applies to Class 2 shares and is described in the “Plan of distribution” section of this prospectus. Returns for Class 1 shares are comparable to those of Class 2 shares because both classes invest in the same portfolio of securities.