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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Money Market Fund May 1, 2013
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. 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) N/A
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 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.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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 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 that are rated in one of the two highest rating categories by at least two rating agencies, and substantially all (at least 95%) that are rated in the highest category by at least two rating agencies.


•  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

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.


•  Money Market risk: An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The credit quality of the Fund's holdings can change rapidly in certain markets, and the default of a single holding could have an adverse impact on the Fund's share price. The actions of a few large investors may have a significant adverse effect on the share prices of all shares of the Fund. In addition, the Fund's returns can be adversely affected when yields on eligible investments are low.

Risk Money Market Fund [Text] rr_RiskMoneyMarketFund An investment in the Fund could decline in value, and you could lose money by investing in the Fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
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 2012, 2011, 2010 and 2009.


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.
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 Closing [Text Block] rr_BarChartClosingTextBlock

Best and Worst Performing Quarters


   

Quarter/Year

 

Total Return

 

Best

 

Fourth quarter 2006

   

1.30

%

 

Worst

 

Fourth quarter 2011

   

(0.05

)%

 
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2006
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (0.05%)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (Index reflects no deduction of any charges against the assets)
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (for periods ended December 31, 2012)
Citigroup 3 month Treasury Bill Index (Index reflects no deduction of any charges against the assets)
  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 0.07%
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.45%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.69%
Money Market Fund Class
  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.15%
Other Expenses rr_OtherExpensesOverAssets 0.15%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.30%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 31
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 97
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 170
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 387
Annual Return 2003 rr_AnnualReturn2003 0.89%
Annual Return 2004 rr_AnnualReturn2004 1.10%
Annual Return 2005 rr_AnnualReturn2005 2.97%
Annual Return 2006 rr_AnnualReturn2006 4.89%
Annual Return 2007 rr_AnnualReturn2007 5.03%
Annual Return 2008 rr_AnnualReturn2008 2.34%
Annual Return 2009 rr_AnnualReturn2009 (0.08%)
Annual Return 2010 rr_AnnualReturn2010 (0.14%)
Annual Return 2011 rr_AnnualReturn2011 (0.17%)
Annual Return 2012 rr_AnnualReturn2012 (0.17%)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (0.17%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 0.35%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 1.66%