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Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName MUTUAL OF AMERICA INVESTMENT CORP
Prospectus Date rr_ProspectusDate May 01, 2018
Bond Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Bond Fund May 1, 2018
Objective [Heading] rr_ObjectiveHeading Investment Objective.
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The Fund seeks current income,
Objective, Secondary [Text Block] rr_ObjectiveSecondaryTextBlock with preservation of shareholders’ capital a secondary objective.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund.
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The table below describes the fees and expenses you may pay if you buy and hold Fund shares. The expenses shown do not include Separate Account expenses which would increase costs if included.
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 result in 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 Fund’s most recently completed fiscal year, the Fund’s portfolio turnover rate was 10.65% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 10.65%
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: (a) 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, (b) a 5% return each year and (c) operating expenses remain the same. The expenses shown do not include Separate Account expenses which would increase costs if included. Although your actual costs may be higher or lower, your cost based on these assumptions would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies.
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock The Fund invests primarily in publicly-traded, investment-grade debt securities.
  • At least 80% of the Fund’s total assets are invested in investment grade securities issued by U.S. corporations or by the U.S. Government or its agencies, such as bonds, notes, debentures, zero coupon securities and mortgage-backed securities. Bonds are debt instruments that can be issued by the federal government, government agencies and subdivisions, states, cities, corporations and other institutions.
  • Although the Fund only purchases investment-grade bonds, the Fund may continue to hold certain corporate bonds in the Fund’s portfolio that are downgraded to below investment grade, commonly referred to as “junk bonds.”
  • The Adviser evaluates each security to be purchased and selects securities based on maturity, credit quality as determined by fundamental analysis and interest income anticipated to be generated.
Risk [Heading] rr_RiskHeading Principal Investment Risks.
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock An investment in the Fund is subject to the following risks which are described in more detail in the Prospectus.
  • General risk: The Fund may not achieve its investment objective. An investment in the Fund could decline in value, and you could lose money by investing in the Fund.
  • Market risk: The risk that prices of securities will go down because of the interplay of market forces may affect a single issuer, industry or sector of the economy or may affect the market as a whole.
  • Interest Rate risk: Securities may lose value as the interest rate changes because bonds tend to decrease in value as interest rates rise.
  • Mortgage risk: The duration of mortgage-related securities and interest rates tend to move together. As interest rates rise, the duration of mortgage-related securities extends and as interest rates fall, mortgage-related securities are often prepaid at a faster rate. Because of interest rate changes, it is not possible to predict the realized yield or average life of a mortgage-backed security.
  • Zero Coupon risk: Zero coupon securities and discount notes do not pay interest prior to maturity and therefore may be more difficult to resell during periods of interest rate changes. The market value of debt securities declines as interest rates rise; therefore the Fund may lose value if it sells zero coupon securities prior to their maturity date. The longer the remaining term to maturity, the greater impact interest rate changes will have on the value of the security.
  • Fixed Income risk: The value of your investment will go up or down depending on movements in the bond markets.
  • Investment management risk: The Fund’s investment results may differ from the results of a comparable bond market and from the results of other funds that invest in the same types of securities or particular debt securities.
  • Interest rate risk: Fixed income securities have an inverse relationship to interest rates, such that as interest rates rise, bond values decrease, and the Fund faces a heightened level of interest rate risk under current conditions because interest rates are near historically low levels.
  • Corporate Debt risk: During periods of economic uncertainty, the value of corporate debt securities may decline relative to the value of U.S. government debt securities. Debt obligations are subject to the risk that issuers may not be able to pay off the principal and interest when due.
  • Credit Risk: Debt obligations are generally subject to the risk that the issuer may be unable to make principal and interest payments when they are due.
  • Call Risk: When interest rates decline, an issuer may have an option to call the securities before maturity, resulting in reduced income.
  • Non-investment grade debt risk: Non-investment grade debt obligations, known as “junk bonds,” have a higher risk of default and tend to be less liquid than higher-rated securities.
  • Liquidity risk: The prices of debt securities may be subject to significant volatility, particularly as markets become less liquid due to limited dealer inventory of corporate bonds.
  • Extension risk: Mortgage-related and other asset-backed securities are subject to the risk that the issuer of such a security pays back the principal of such an obligation later than expected. This may occur when interest rates rise, and this may negatively affect fund returns.
Risk Lose Money [Text] rr_RiskLoseMoney An investment in the Fund could decline in value, and you could lose money by investing in the Fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance/Annual Return.
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below show the annual return and average annual returns of the Fund.

Below the bar chart are the Fund’s highest and lowest total returns for any calendar quarter during the period covered by the chart, showing the volatility of the Fund’s total returns. The numbers in parentheses are negative, representing a loss of principal.

The information indicates some of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual returns for one, five, and ten years compare to those of a broad-based, unmanaged index for those periods. A fund’s past performance does not necessarily indicate how it will perform in the future.

The total returns and average annual total returns shown do not include charges against the assets of the Separate Accounts that purchase Fund shares. If these charges were reflected, returns would be less than those shown. Updated performance information is available at no cost online at http://www.mutualofamerica.com or by calling 1-800-468-3785.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and table below show the annual return and average annual returns of the Fund.

The information indicates some of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual returns for one, five, and ten years compare to those of a broad-based, unmanaged index for those periods.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-468-3785
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress http://www.mutualofamerica.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture A fund’s past performance does not necessarily indicate how it will perform in the future.
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The total returns and average annual total returns shown do not include charges against the assets of the Separate Accounts that purchase Fund shares. If these charges were reflected, returns would be less than those shown.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best and Worst Performing Quarters

     Quarter/Year    Total Return  
Best   
Second quarter 2009
      5.92 % 
Worst   
Second quarter 2013
      (2.68 )% 
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for periods ended December 31, 2017)
Bond Fund | Bond Fund Class  
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees (fees paid directly from your investment) rr_ShareholderFeeOther
Management Fees rr_ManagementFeesOverAssets 0.39%
Other Expenses rr_OtherExpensesOverAssets 0.06%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.45%
1 Year rr_ExpenseExampleYear01 $ 46
3 Years rr_ExpenseExampleYear03 146
5 Years rr_ExpenseExampleYear05 255
10 Years rr_ExpenseExampleYear10 $ 580
2008 rr_AnnualReturn2008 (1.75%)
2009 rr_AnnualReturn2009 14.61%
2010 rr_AnnualReturn2010 7.29%
2011 rr_AnnualReturn2011 7.30%
2012 rr_AnnualReturn2012 5.79%
2013 rr_AnnualReturn2013 (0.91%)
2014 rr_AnnualReturn2014 6.31%
2015 rr_AnnualReturn2015 0.33%
2016 rr_AnnualReturn2016 4.71%
2017 rr_AnnualReturn2017 3.62%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.92%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2013
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.68%)
Past One Year rr_AverageAnnualReturnYear01 3.62%
Past Five Years rr_AverageAnnualReturnYear05 2.77%
Past Ten Years rr_AverageAnnualReturnYear10 4.61%
Bond Fund | Bloomberg Barclays U.S. Aggregate Bond Index (Index reflects no deduction for fees and expenses)  
Risk/Return: rr_RiskReturnAbstract  
Past One Year rr_AverageAnnualReturnYear01 3.54%
Past Five Years rr_AverageAnnualReturnYear05 2.10%
Past Ten Years rr_AverageAnnualReturnYear10 4.01%