XML 17 R11.htm IDEA: XBRL DOCUMENT v2.4.0.6
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Jul. 31, 2012
Registrant Name dei_EntityRegistrantName OPPENHEIMER MONEY MARKET FUND INC
Central Index Key dei_EntityCentralIndexKey 0000074673
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Nov. 20, 2012
Document Effective Date dei_DocumentEffectiveDate Nov. 21, 2012
Prospectus Date rr_ProspectusDate Nov. 21, 2012
(Oppenheimer Money Market Fund)
  
Risk/Return: rr_RiskReturnAbstract  
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

Investment Objective. The Fund seeks the maximum current income that is consistent with stability of principal. The Fund is a money market fund.
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

Fees and Expenses of the Fund. This table describes the fees and expenses that you may pay if you buy and hold or redeem shares of the Fund. You may qualify for sales charge discounts if you (or you and your spouse) invest, or agree to invest in the future, at least $25,000 in certain funds in the Oppenheimer family of funds. More information about these and other discounts is available from your financial professional and in the section "About Your Account" beginning on page 9 of the prospectus and in the sections "How to Buy Shares" beginning on page 34 and "Appendix A" in the Fund's Statement of Additional Information.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

Shareholder Fees. The Fund does not charge any initial sales charge to buy shares or to reinvest dividends. There are no exchange fees or redemption fees and no contingent deferred sales charges (unless you buy Fund shares by exchanging Class A shares of other Oppenheimer funds that were purchased subject to a contingent deferred sales charge).
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)
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you (or you and your spouse) invest, or agree to invest in the future, at least $25,000 in certain funds in the Oppenheimer family of funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 25,000
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

Example. The following 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 a class of shares of the Fund for the time periods indicated. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your expenses would be as follows:

Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption

If shares are redeemed

Expense Example, No Redemption, By Year, Caption [Text] rr_ExpenseExampleNoRedemptionByYearCaption

If shares are not redeemed

Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Principal Investment Strategies. The Fund is a money market fund that invests in a variety of money market instruments to seek current income. Money market instruments are short-term, high-quality, dollar-denominated debt instruments issued by the U.S. Government, domestic and foreign corporations and financial institutions, and other entities. Money market instruments include bank obligations, repurchase agreements, commercial paper, and other short-term corporate and governmental debt obligations.

To be considered "high-quality," a debt instrument must be rated in one of the two highest credit-quality categories for short-term securities by a nationally recognized statistical rating service or, if a security is unrated, it must be determined by the Fund's investment manager, OppenheimerFunds, Inc. (the "Manager"), under the supervision of the Fund's Board, to be of comparable quality to rated securities in one of those two categories.
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

Principal Risks. All investments carry risks to some degree. The Fund's investments are subject to changes in their value from a number of factors. However, the Fund's investments must meet strict standards set by its Board of Directors and special rules under Federal law for money market funds. Those requirements include maintaining high credit quality, a short average maturity and diversification of the Fund's investments among issuers. Those provisions are designed to help minimize credit risks, to reduce the effects of changes in prevailing interest rates and to reduce the effect on the Fund's portfolio of a default by any one issuer. Since income on short-term securities tends to be lower than income on longer-term debt securities, the Fund's yield will likely be lower than the yield on longer-term fixed-income funds.

Even so, there are risks that an issuer of an obligation that the Fund holds might have its credit rating downgraded or might default on its obligations, or that interest rates might rise sharply, causing the value of the Fund's investments to fall. Also, there is the risk that the value of your investment could be eroded over time by the effects of inflation, or that poor security selection could cause the Fund to underperform other funds that have a similar objective. If there is an unexpectedly high demand for the redemption of Fund shares, the Fund might need to sell portfolio securities prior to their maturity, possibly at a loss. As a result, there is a risk that the Fund's shares could fall below $1.00 per share.

Interest Rate Risk. The values of debt securities usually change when prevailing interest rates change. When interest rates fall, the values of already-issued debt securities generally rise.

When interest rates rise, the values of already-issued debt securities generally fall. The values of longer-term debt securities usually change more when interest rates change than the values of shorter-term debt securities.

Credit Risk. Debt securities are also subject to credit risk, which is the risk that the issuer of a security might not make principal or interest payments on the security when they are due. If the issuer fails to pay interest, the Fund's income might be reduced, and if the issuer fails to pay interest or repay principal, the value of the security might fall.

Fixed-Income Market Risks. Economic and other market developments can adversely affect fixed-income securities markets in the United States, Europe and elsewhere. At times, participants in debt securities markets may develop concerns about the ability of certain issuers of debt securities to make timely principal and interest payments, or they may develop concerns about the ability of financial institutions that make markets in certain debt securities to facilitate an orderly market. Those concerns can cause increased volatility in those debt securities or debt securities markets. Under some circumstances, as was the case during the latter half of 2008 and early 2009, those concerns could cause reduced liquidity in certain debt securities markets. A lack of liquidity or other adverse credit market conditions may hamper the Fund's ability to sell the debt securities in which it invests or to find and purchase suitable debt instruments.

Who Is the Fund Designed For? The Fund is designed for investors who want to earn income at money market rates while seeking to preserve the value of their investment and maintaining easy access to their investment through checkwriting and wire redemption privileges. The Fund will invest in a variety of money market instruments to seek current income and stability of principal and to try to maintain a stable share price of $1.00. The Fund is not a complete investment program.

An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the Fund.

Risk Lose Money [Text] rr_RiskLoseMoney Although the Fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the Fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The Fund's Past Performance. The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing the Fund's average annual returns for 1, 5 and 10 year periods. The Fund's past investment performance is not necessarily an indication of how the Fund will perform in the future. More recent performance information is available by calling the toll-free number on the back of this prospectus and on the Fund's website at:

https://www.oppenheimerfunds.com/fund/MoneyMarketFundInc.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1.800.225.5677
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress https://www.oppenheimerfunds.com/fund/MoneyMarketFundInc
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund's past investment performance is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

During the period shown, the highest return for a calendar quarter was 1.22% (3rd Qtr 07) and the lowest return was 0.00% (most recently in 4th Qtr 11). For the period from January 1, 2012 through September 30, 2012, the cumulative return before taxes was 0.01%.
Performance Table Heading rr_PerformanceTableHeading

Average Annual Total Returns for the periods ended December 31, 2011
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

The Fund's performance reflects reinvestment of all dividends and capital gains distributions.

The total returns are not the Fund's current yield. The Fund's yield more closely reflects the Fund's current earnings. To obtain the Fund's current 7-day yield information, please call the Transfer Agent toll-free at 1.800.CALL OPP (225.5677).

(Oppenheimer Money Market Fund) | Class A
  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.25%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.66%
Fee Waiver and/or Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.35%) [1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement rr_NetExpensesOverAssets 0.31%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 32
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 177
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 334
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 792
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 32
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 177
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 334
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 792
Annual Return 2002 rr_AnnualReturn2002 1.35%
Annual Return 2003 rr_AnnualReturn2003 0.52%
Annual Return 2004 rr_AnnualReturn2004 0.75%
Annual Return 2005 rr_AnnualReturn2005 2.71%
Annual Return 2006 rr_AnnualReturn2006 4.56%
Annual Return 2007 rr_AnnualReturn2007 4.88%
Annual Return 2008 rr_AnnualReturn2008 2.70%
Annual Return 2009 rr_AnnualReturn2009 0.23%
Annual Return 2010 rr_AnnualReturn2010 0.01%
Annual Return 2011 rr_AnnualReturn2011 0.01%
Year to Date Return, Label rr_YearToDateReturnLabel For the period from January 1, 2012 through September 30, 2012, the cumulative return before taxes was 0.01%.
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Sep. 30, 2012
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.01%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest return for a calendar quarter was 1.22% (3rd Qtr 07)
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.22%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest return was 0.00% (most recently in 4th Qtr 11)
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
1 Year rr_AverageAnnualReturnYear01 0.01%
5 Years rr_AverageAnnualReturnYear05 1.55%
10 Years (or life of class, if less) rr_AverageAnnualReturnYear10 1.76%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 17, 1974
(Oppenheimer Money Market Fund) | Class Y
  
Risk/Return: rr_RiskReturnAbstract  
Management Fees rr_ManagementFeesOverAssets 0.41%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.03%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.44%
Fee Waiver and/or Expense Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.14%) [1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement rr_NetExpensesOverAssets 0.30%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 31
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 127
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 233
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 542
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 31
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 127
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 233
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 542
1 Year rr_AverageAnnualReturnYear01 0.01%
5 Years rr_AverageAnnualReturnYear05 1.63%
10 Years (or life of class, if less) rr_AverageAnnualReturnYear10 2.20%
Inception Date rr_AverageAnnualReturnInceptionDate Aug. 27, 2004
[1] The Manager has voluntarily undertaken to waive fees and/or reimburse expenses to the extent necessary to assist the Fund in attempting to maintain a positive yield. There is no guarantee that the Fund will maintain a positive yield. The Manager is permitted to recapture previously waived and/or reimbursed fees in any given fiscal year if the recapture would not: (1) cause the Fund to generate a negative daily yield, and (2) exceed amounts previously waived and/or reimbursed under this arrangement during the current and prior three fiscal years. The reimbursement to the Manager of such previous waivers and reimbursements would not include any portion of distribution and/or service fees. This recapture could negatively affect each share class's future yield. This undertaking may not be amended or withdrawn until one year from the date of this prospectus.