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Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName MUTUAL OF AMERICA INVESTMENT CORP
Prospectus Date rr_ProspectusDate May 01, 2020
Money Market Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Money Market Fund May 1, 2020
Objective [Heading] rr_ObjectiveHeading Investment Objective.
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The Fund seeks current income to the extent consistent with maintenance of liquidity, investment quality and stability of capital.
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. For investments through an insurance company separate account, note that the expenses shown do not include Separate Account expenses or variable contract 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.
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 or hold all of your shares at the end of those periods, (b) a 5% return each year and (c) operating expenses remain the same. For investments through an insurance company separate account, note that the expenses shown do not include Separate Account expenses or variable contract 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 in money market instruments that meet certain requirements. The Fund is considered to be an institutional money market fund because it is not limited to investments by natural persons, and it does not maintain a stable net asset value.
  • The dollar weighted average maturity of the instruments the Fund holds will be short-term — 60 days or less.
  • The Fund will purchase only securities with a remaining maturity of 397 calendar days or less that present minimal credit risks to the Fund.
  • The Fund will diversify its investments, limiting holdings in the securities of any one issuer (except the U.S. Government or its agencies) to 5% of assets.
Risk [Heading] rr_RiskHeading Principal Investment Risks.
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock As with any mutual fund, loss of money is a risk of investing in the Fund. Additionally, 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. Events such as war, acts of terrorism, social unrest, natural disasters, public health emergencies and other unforeseen events could also significantly impact issuers, economies and markets generally.
  • Money Market risk: You could lose money by investing in the Fund. Because the share price of the Fund will fluctuate, when you sell your shares they may be worth more or less than what you originally paid for them. The Board of Directors of the Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors, and a fee may automatically be imposed based on the Fund’s liquidity level. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time. In addition, the Fund’s returns can be adversely affected when yields on eligible investments are low.
  • U.S. Government Securities risk: The Fund invests in securities issued or guaranteed by the U.S. government or its agencies. U.S. government securities are subject to market risk, interest rate risk and credit risk. U.S. government securities include zero coupon securities, which tend to be subject to greater price volatility than interest-paying securities of similar maturities.
  • Interest Rate risk: Securities may lose value as interest rates change because bonds tend to decrease in value as interest rates rise. In general, the longer the term to maturity, the greater impact interest rate changes will have on the value of a security.
  • Management risk: The investment techniques and risk analyses applied by the Fund may not produce the desired results, and that legislative, regulatory, or tax restrictions, policies or developments may affect the investment techniques available to the Fund. There is no guarantee that the investment objective of the Fund will be achieved.
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.
Risk Money Market Fund Price Fluctuates [Text] rr_RiskMoneyMarketFundPriceFluctuates Because the share price of the Fund will fluctuate, when you sell your shares they may be worth more or less than what you originally paid for them.
Risk Money Market Fund May Impose Fees or Suspend Sales [Text] rr_RiskMoneyMarketFundMayImposeFeesOrSuspendSales The Board of Directors of the Fund may impose a fee upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund’s liquidity falls below required minimums because of market conditions or other factors, and a fee may automatically be imposed based on the Fund’s liquidity level.
RIsk Not Insured [Text] rr_RiskNotInsured An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund Sponsor May Not Provide Support [Text] rr_RiskMoneyMarketFundSponsorMayNotProvideSupport The Fund’s sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time.
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. Investors experienced negative returns and the Fund lost money for periods of time in each calendar year from 2009 through 2018.

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.

For investments through an insurance company separate account, note that 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 For investments through an insurance company separate account, note that 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   
First quarter 2019
     0.58 % 
Worst   
Fourth quarter 2011
     (0.05 )% 
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (for periods ended December 31, 2019)
Money Market Fund | Money Market Fund Class  
Risk/Return: rr_RiskReturnAbstract  
Shareholder Fees (fees paid directly from your investment) rr_ShareholderFeeOther
Management Fees rr_ManagementFeesOverAssets 0.15%
Other Expenses rr_OtherExpensesOverAssets 0.08%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.23%
1 Year rr_ExpenseExampleYear01 $ 24
3 Years rr_ExpenseExampleYear03 74
5 Years rr_ExpenseExampleYear05 130
10 Years rr_ExpenseExampleYear10 296
1 Year rr_ExpenseExampleNoRedemptionYear01 24
3 Years rr_ExpenseExampleNoRedemptionYear03 74
5 Years rr_ExpenseExampleNoRedemptionYear05 130
10 Years rr_ExpenseExampleNoRedemptionYear10 $ 296
2010 rr_AnnualReturn2010 (0.14%)
2011 rr_AnnualReturn2011 (0.17%)
2012 rr_AnnualReturn2012 (0.17%)
2013 rr_AnnualReturn2013 (0.16%)
2014 rr_AnnualReturn2014 (0.14%)
2015 rr_AnnualReturn2015 (0.11%)
2016 rr_AnnualReturn2016 0.14%
2017 rr_AnnualReturn2017 0.70%
2018 rr_AnnualReturn2018 1.71%
2019 rr_AnnualReturn2019 2.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 0.58%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (0.05%)
Past One Year rr_AverageAnnualReturnYear01 2.01%
Past Five Years rr_AverageAnnualReturnYear05 0.89%
Past Ten Years rr_AverageAnnualReturnYear10 0.36%
Money Market Fund | FTSE 3-Month Treasury Bill Index (Index reflects no deduction for fees and expenses)  
Risk/Return: rr_RiskReturnAbstract  
Past One Year rr_AverageAnnualReturnYear01 2.25%
Past Five Years rr_AverageAnnualReturnYear05 1.05%
Past Ten Years rr_AverageAnnualReturnYear10 0.56%