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AMERICAN FUNDS FUNDAMENTAL INVESTORS  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading AMERICAN FUNDS FUNDAMENTAL INVESTORS
Objective [Heading] rr_ObjectiveHeading Investment objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund’s investment objective is to achieve long-term growth of capital and income.
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 and hold shares of the fund. In addition to the fees and expenses described below, you may also be required to pay brokerage commissions on purchases and sales of Class F-2, F-3, 529-F-2 or 529-F-3 shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in American Funds. More information about these and other discounts is available from your financial professional, in the “Sales charge reductions and waivers” sections on page 30 of the prospectus and on page 69 of the fund’s statement of additional information, and in the sales charge waiver appendix to this prospectus.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
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 and may result in higher taxes when fund shares are held in a taxable account. 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 40% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 40.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in American Funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 25,000
Expenses Restated to Reflect Current [Text] rr_ExpensesRestatedToReflectCurrent Restated to reflect current fees.
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 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 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. You may be required to pay brokerage commissions on your purchases and sales of Class F-2, F-3, 529-F-2 or 529-F-3 shares of the fund, which are not reflected in the example.

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:
Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption For the share classes listed to the right, you would pay the following if you did not redeem your shares:
Strategy [Heading] rr_StrategyHeading Principal investment strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The fund seeks to invest primarily in common stocks of companies that appear to offer superior opportunities for capital growth and most of which have a history of paying dividends. In addition, the fund may invest significantly in securities of issuers domiciled outside the United States.

The investment adviser uses a system of multiple portfolio managers in managing the fund’s assets. Under this approach, the portfolio of the fund is divided into segments managed by individual managers.

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 invest in attractively valued companies that, in its opinion, represent good, long-term investment opportunities. Securities may be sold when the investment adviser believes that they no longer represent relatively attractive investment opportunities.
Risk [Heading] rr_RiskHeading Principal risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

This section describes the principal risks associated with investing in the fund. You may lose money by investing in the fund. The likelihood of loss may be greater if you invest for a shorter period of time. Investors in the fund should have a long-term perspective and be able to tolerate potentially sharp declines in value.

Market conditions — The prices of, and the income generated by, the common stocks and other 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; overall market changes; local, regional or global political, social or economic instability; governmental, governmental agency or central bank responses to economic conditions; 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) 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.

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 related to the issuer, 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.

Investing in growth-oriented stocks — Growth-oriented common stocks and other equity-type securities (such as preferred stocks, convertible preferred stocks and convertible bonds) may involve larger price swings and greater potential for loss than other types of investments.

Investing in income-oriented stocks — The value of the fund’s securities and income provided by the fund may be reduced by changes in the dividend policies of, and the capital resources available for dividend payments at, the companies in which the fund invests.

Investing outside the United States — Securities of issuers domiciled outside the United States, or with significant operations or revenues 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 operate or generate revenue. 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 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 accounting practices and different regulatory, legal and reporting standards and practices, 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. The risks of investing outside the United States may be heightened in connection with investments in emerging markets.

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.

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. You should consider how this fund fits into your overall investment program.
Risk Lose Money [Text] rr_RiskLoseMoney You may lose money by investing in the fund.
RIsk Not Insured [Text] rr_RiskNotInsured 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Investment results
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The following bar chart shows how the fund’s investment results 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 MSCI World Index reflects certain market sectors in which the fund may invest. The Lipper Growth and Income Funds Index includes the fund and other 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. Prior to October 30, 2020, certain fees, such as 12b-1 fees, were not charged on Class 529-F-1 shares. If these expenses had been deducted, results would have been lower. Investment results for Class 529-F-2 and Class 529-F-3 shares will be shown after these share classes have had annual returns for at least one calendar year. Class 529-F-2 and Class 529-F-3 shares will invest in the same securities as the other share classes of the fund but their results may vary from that of other share classes based on their respective fees and expenses. If expenses of the Class 529-F-2 and Class 529-F-3 are higher, then results would be lower. Updated information on the fund’s investment results can be obtained by visiting capitalgroup.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart shows how the fund’s investment results 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 MSCI World Index reflects certain market sectors in which the fund may invest. The Lipper Growth and Income Funds Index includes the fund and other funds that disclose investment objectives and/or strategies reasonably comparable to those of the fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress capitalgroup.com
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 for Class A shares (Results do not include a sales charge; if a sales charge were included, results would be lower.)
Bar Chart Narrative [Text Block] rr_BarChartNarrativeTextBlock

The following bar chart shows how the fund’s investment results 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 Results do not include a sales charge; if a sales charge were included, results would be lower.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Highest/Lowest quarterly results during this period were:

 

Highest 12.07% (quarter ended September 30, 2010)

 

Lowest -16.93% (quarter ended September 30, 2011)

 

The fund's total return for the nine months ended September 30, 2020, was 0.85%.
Year to Date Return, Label rr_YearToDateReturnLabel The fund's total return for the nine months ended
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2020
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.85%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.07%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (16.93%)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest individual federal income tax rates in effect during each year of the periods shown and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Your actual after-tax returns depend on your individual tax situation and likely will differ from the results shown above. In addition, after-tax returns are not relevant if you hold your fund shares through a tax-favored arrangement, such as a 401(k) plan, individual retirement account (IRA) or 529 college savings plan.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown only for Class A shares; after-tax returns for other share classes will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns are shown only for Class A shares; after-tax returns for other share classes will vary. After-tax returns are calculated using the highest individual federal income tax rates in effect during each year of the periods shown and do not reflect the impact of state and local taxes. Your actual after-tax returns depend on your individual tax situation and likely will differ from the results shown above. In addition, after-tax returns are not relevant if you hold your fund shares through a tax-favored arrangement, such as a 401(k) plan, individual retirement account (IRA) or 529 college savings plan.
Average Annual Return, Caption rr_AverageAnnualReturnCaption Average annual total returns For the periods ended December 31, 2019 (with maximum sales charge):
AMERICAN FUNDS FUNDAMENTAL INVESTORS | S&P 500 Index (reflects no deductions for sales charges, account fees, expenses or U.S. federal income taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 31.49%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 11.70%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 13.56%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 11.78%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 1978
AMERICAN FUNDS FUNDAMENTAL INVESTORS | MSCI® World Index (reflects no deductions for sales charges, account fees, expenses or U.S. federal income taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.67%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.74%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 9.47%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.60%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 1978
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Lipper Growth and Income Funds Index (reflects no deductions for sales charges, account fees or U.S. federal income taxes)  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 24.74%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.52%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 10.40%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.55%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 1978
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class A  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.13% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.62%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock A contingent deferred sales charge of 1.00% applies on certain redemptions made within 18 months following purchases of $1 million or more made without an initial sales charge. Contingent deferred sales charge is calculated based on the lesser of the offering price and market value of shares being sold.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 635
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 762
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 901
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,305
Annual Return 2010 rr_AnnualReturn2010 14.05%
Annual Return 2011 rr_AnnualReturn2011 (1.89%)
Annual Return 2012 rr_AnnualReturn2012 17.14%
Annual Return 2013 rr_AnnualReturn2013 31.49%
Annual Return 2014 rr_AnnualReturn2014 8.96%
Annual Return 2015 rr_AnnualReturn2015 3.38%
Annual Return 2016 rr_AnnualReturn2016 12.54%
Annual Return 2017 rr_AnnualReturn2017 23.37%
Annual Return 2018 rr_AnnualReturn2018 (6.60%)
Annual Return 2019 rr_AnnualReturn2019 27.61%
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 20.28%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.02%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.71%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 12.29%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 1978
Thirty Day Yield Caption rr_ThirtyDayYieldCaption Class A annualized 30–day yield at June 30, 2020:
Thirty Day Yield Phone rr_ThirtyDayYieldPhone (800) 325-3590
Thirty Day Yield rr_ThirtyDayYield 1.19%
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class A | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 18.23%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.18%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 10.39%
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class A | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 13.37%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 7.62%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 9.47%
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class 529-A  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 3.50%
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00% [1]
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.23%
Other expenses rr_OtherExpensesOverAssets 0.18% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.65%
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock A contingent deferred sales charge of 1.00% applies on certain redemptions made within 18 months following purchases of $1 million or more made without an initial sales charge. Contingent deferred sales charge is calculated based on the lesser of the offering price and market value of shares being sold.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 414
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 551
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 700
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,132
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 23.08%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.45%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.89%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.11%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Feb. 15, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class C  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other expenses rr_OtherExpensesOverAssets 0.13% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 1.37%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 239
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 434
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 750
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,441
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 139
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 434
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 750
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,441
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 25.66%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.46%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.66%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.21%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 15, 2001
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class 529-C  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other expenses rr_OtherExpensesOverAssets 0.18% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 1.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 245
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 449
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 776
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,209
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 145
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 449
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 776
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,209
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 25.59%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.39%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.84%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.07%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Feb. 15, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class 529-E  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other expenses rr_OtherExpensesOverAssets 0.14% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.88%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 90
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 281
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 488
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,084
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.24%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.99%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.01%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.71%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 07, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class T  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.50%
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.11% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.60%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 310
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 437
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 576
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 981
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class 529-T  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.50%
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.17% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.66%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 316
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 456
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 609
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,052
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class F-1  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.16% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.65%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 66
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 208
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 362
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 810
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.53%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 11.26%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.32%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.55%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Mar. 15, 2001
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class F-2  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.15% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.39%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 40
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 125
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 219
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 493
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.87%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 11.56%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.61%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.08%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 01, 2008
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class F-3  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.05% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.29%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 30
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 93
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 163
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 368
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 28.01%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 12.94%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Jan. 27, 2017
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class 529-F-1  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25% [2]
Other expenses rr_OtherExpensesOverAssets 0.18% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.67%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 68
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 214
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 373
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 835
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.84%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 11.49%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.53%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 11.25%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 23, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class 529-F-2  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.16% [3]
Total annual fund operating expenses rr_ExpensesOverAssets 0.40%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Based on estimated amounts for the current fiscal year.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 41
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 128
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 224
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 505
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess Investment results for Class 529-F-2 and Class 529-F-3 shares will be shown after these share classes have had annual returns for at least one calendar year.
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class 529-F-3  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.10% [3]
Total annual fund operating expenses rr_ExpensesOverAssets 0.34%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Based on estimated amounts for the current fiscal year.
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 35
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 109
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 191
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 431
Performance One Year or Less [Text] rr_PerformanceOneYearOrLess Investment results for Class 529-F-2 and Class 529-F-3 shares will be shown after these share classes have had annual returns for at least one calendar year.
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-1  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other expenses rr_OtherExpensesOverAssets 0.15% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 1.39%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 142
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 440
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 761
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,669
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 26.60%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.44%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.49%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.82%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Jun. 19, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-2  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.75%
Other expenses rr_OtherExpensesOverAssets 0.39% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 1.38%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 140
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 437
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 755
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,657
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 26.62%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.46%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 11.51%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 8.48%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate May 21, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-3  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other expenses rr_OtherExpensesOverAssets 0.19% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.93%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 95
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 296
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 515
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,143
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.17%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.95%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.00%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.15%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Jun. 04, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-4  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.14% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.63%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 64
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 202
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 351
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 786
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.57%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 11.28%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.33%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.86%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Jul. 25, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-5  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.09% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.33%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 34
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 106
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 185
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 418
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.95%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 11.62%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.67%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 9.57%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate May 15, 2002
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-6  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.04% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.28%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 29
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 90
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 157
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 356
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 28.01%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 11.67%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 12.73%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 14.64%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate May 01, 2009
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-2E  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.60%
Other expenses rr_OtherExpensesOverAssets 0.24% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 1.08%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 110
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 343
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 595
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,317
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 26.99%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 10.84%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 10.40%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Aug. 29, 2014
AMERICAN FUNDS FUNDAMENTAL INVESTORS | Class R-5E  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) (as a percentage of the amount redeemed) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Maximum sales charge (load) imposed on reinvested dividends rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther none
Redemption or exchange fees rr_RedemptionFeeOverRedemption none
Management fees rr_ManagementFeesOverAssets 0.24%
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.18% [2]
Total annual fund operating expenses rr_ExpensesOverAssets 0.42%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 43
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 135
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 235
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 530
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 27.85%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception 12.64%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Nov. 20, 2015
[1] A contingent deferred sales charge of 1.00% applies on certain redemptions made within 18 months following purchases of $1 million or more made without an initial sales charge. Contingent deferred sales charge is calculated based on the lesser of the offering price and market value of shares being sold.
[2] Restated to reflect current fees.
[3] Based on estimated amounts for the current fiscal year.