XML 16 R13.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 Dec. 31, 2011
Registrant Name dei_EntityRegistrantName ROCHESTER FUND MUNICIPALS
Central Index Key dei_EntityCentralIndexKey 0000093621
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Mar. 29, 2012
Document Effective Date dei_DocumentEffectiveDate Apr. 02, 2012
Prospectus Date rr_ProspectusDate Apr. 02, 2012
(Oppenheimer Rochester® Fund Municipals)
  
Risk/Return: rr_RiskReturnAbstract  
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

Investment Objective. The Fund seeks to provide as high a level of income exempt from federal income tax and New York State and New York City personal income taxes as is consistent with its investment policies and prudent investment management while seeking preservation of shareholders' capital.
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 $50,000 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 15 of the prospectus and in the sections "How to Buy Shares" beginning on page 54 and "Appendix A" in the Fund's Statement of Additional Information.
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 [Text Block] rr_PortfolioTurnoverTextBlock

Portfolio Turnover. 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 the annual fund operating expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 11% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 11.00%
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 $50,000 in certain funds in the Oppenheimer family of funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount 50,000
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 invests mainly in New York municipal securities that pay interest that, in the opinion of counsel to the issuer of each security, is exempt from federal and New York personal income taxes. To seek its investment objective:

  • As a fundamental policy, under normal market conditions, the Fund invests at least 80% of its net assets (plus borrowings for investment purposes) in tax-exempt securities, including securities subject to alternative minimum tax, and

  • The Fund can invest up to 25% of its total assets in below-investment-grade securities (commonly called "junk bonds"). Investment-grade securities are rated within one of the four highest rating categories of a nationally recognized statistical rating organization such as Standard & Poor's (AAA, AA, A or BBB) (or in the case of unrated securities, determined by the Fund's investment adviser to be comparable to securities rated investment-grade). The Fund may also invest in unrated securities, in which case the Fund's investment adviser, OppenheimerFunds, Inc., internally assigns ratings to those securities, after assessing their credit quality and other factors, in investment-grade or below-investment grade categories similar to those of nationally recognized statistical rating organizations. There can be no assurance, nor is it intended, that the Manager's credit analysis process is consistent or comparable with the credit analysis process used by a nationally recognized statistical rating organization.

The Fund's tax-exempt investments can include a wide variety of debt obligations, including securities issued by:

  • the State of New York and its political subdivisions (for example, cities, towns and counties),

  • agencies, public authorities and instrumentalities (these are state-chartered corporations) of the State of New York, and

  • territories, commonwealths and possessions of the United States (for example, Puerto Rico, Guam and the Virgin Islands) that pay interest that, in the opinion of counsel to the issuer of each security, is exempt from federal, New York State and New York City personal income taxes.

These are referred to as "New York municipal securities" in this prospectus.

The Fund's investments have no maturity limitations and can include municipal bonds, municipal notes, and interests in municipal leases. At times, the Fund may focus on longer-term securities to seek higher yields. This portfolio strategy is subject to change. The Fund can buy general obligation bonds and revenue bonds, including "private activity" municipal securities that pay income subject to alternative minimum taxation. To the extent the Fund invests in securities that may pay interest subject to alternative minimum taxation, those securities will be counted towards the Fund's policy regarding minimum investments in tax-exempt securities as described above. The Fund may invest a substantial percentage of its assets in "callable" securities, which may be redeemed by the issuer before their maturity date.

The Fund can invest in inverse floating rate securities, a variable rate instrument, to seek increased income and return. Inverse floating rate securities are leveraged instruments and the extent of their leverage will vary depending on the security's characteristics. The Fund limits its investments in inverse floating rate securities as further described in this Prospectus under "Principal Risks."

The Fund can borrow money to purchase additional securities, another form of leverage. Although the amount of borrowing will vary from time to time, the amount of leveraging from borrowings will not exceed one-third of the Fund's total assets.

In selecting securities for the Fund, the portfolio managers generally look for triple tax-exempt municipal securities using a variety of factors. Currently, the portfolio managers look for a wide range of securities of different issuers within the state of New York, including those of different agencies and municipalities. They also focus on finding primarily investment-grade securities that offer high-income opportunities, including unrated bonds and securities of smaller issuers that might be overlooked by other investors and funds.

These factors may change over time and may vary in particular cases. The portfolio managers may consider selling a security if any of these factors no longer applies to a security purchased for the Fund, but are not required to do so.
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

Principal Risks. The price of the Fund's shares can go up and down substantially. The value of the Fund's investments may change because of broad changes in the markets in which the Fund invests or because of poor investment selection, which could cause the Fund to underperform other funds with similar investment objectives. There is no assurance that the Fund will achieve its investment objective. When you redeem your shares, they may be worth more or less than what you paid for them. These risks mean that you can lose money by investing in the Fund.

Main Risks of Investing in Municipal Securities. Municipal securities may be subject to interest rate risk, credit risk, credit spread risk, extension risk, reinvestment risk and prepayment risk. Interest rate risk is the risk that when prevailing interest rates fall, the values of already-issued debt securities generally rise; and when prevailing interest rates rise, the values of already-issued debt securities generally fall, and they may be worth less than the amount the Fund paid for them. When interest rates change, the values of longer-term debt securities usually change more than the values of shorter-term debt securities. Credit risk is the risk that the issuer of a security might not make interest and principal payments on the security as they become due. If an issuer fails to pay interest or repay principal, the Fund's income or share value might be reduced. Adverse news about an issuer or a downgrade in an issuer's credit rating, for any reason, can also reduce the market value of the issuer's securities. "Credit spread" is the difference in yield between securities that is due to differences in their credit quality. There is a risk that credit spreads may increase when the market expects lower-grade bonds to default more frequently. Widening credit spreads may quickly reduce the market values of the Fund's lower-rated and unrated securities. Extension risk is the risk that an increase in interest rates could cause principal payments on a debt security to be repaid at a slower rate than expected. Extension risk is particularly prevalent for a callable security where an increase in interest rates could result in the issuer of that security choosing not to redeem the security as anticipated on the security's call date. Such a decision by the issuer could have the effect of lengthening the debt security's expected maturity, making it more vulnerable to interest rate risk and reducing its market value. Reinvestment risk is the risk that when interest rates fall the Fund may be required to reinvest the proceeds from a security's sale or redemption at a lower interest rate. Callable bonds are generally subject to greater reinvestment risk than non-callable bonds. Prepayment risk is the risk that the issuer may redeem the security prior to the expected maturity or that borrowers may repay the loans that underlie these securities more quickly than expected, thereby causing the issuer of the security to repay the principal prior to the expected maturity. The Fund may need to reinvest the proceeds at a lower interest rate, reducing its income.

Special Risks of Below-Investment-Grade Securities. Below-investment-grade debt securities may be subject to greater price fluctuations and have a greater risk that the issuer might not be able to pay interest and principal when due. The market for below-investment-grade securities may be less liquid and they may be harder to value or to sell at an acceptable price, especially during times of market volatility or decline.

Because the Fund can invest up to 25% of its assets in below-investment-grade securities, the Fund's credit risks are greater than those of funds that buy only investment-grade securities. This restriction is applied at the time of purchase and the Fund may continue to hold a security whose credit rating has been lowered or, in case of an unrated security, after the Fund's adviser has changed its assessment of the security's credit quality. As a result, credit rating downgrades or other market fluctuations may cause the Fund's holdings of below-investment-grade securities to exceed this restriction for an extended period of time. If the Fund has more than 25% of its total assets invested in below-investment-grade securities, the adviser will not purchase additional below-investment-grade securities until the level of holdings in those securities no longer exceeds the restriction.

The Fund generally will not invest more than 5% of its net assets in the securities of an issuer if the securities are rated "B" or below by a nationally recognized statistical rating organization or, if unrated, assigned a similar rating by the adviser.

Special Risks of New York Municipal Securities. Because the Fund invests primarily in New York municipal securities, the value of its portfolio investments will be highly sensitive to events affecting the financial stability of the state of New York and its municipalities, agencies, authorities and other instrumentalities that issue those securities. Changes in legislation or policy, erosion of the tax base, the effects of terrorist acts or natural disasters, or other economic or credit problems may have a significant negative impact on the value of state or local securities.

These risks also apply to securities of issuers of U.S. territories, commonwealths or possessions located outside of New York such as Puerto Rico, Guam, the Northern Mariana Islands and the Virgin Islands.

Municipal Market Volatility and Illiquidity. The municipal bond market can be susceptible to unusual volatility, particularly for lower-rated and unrated securities. Liquidity can be reduced unpredictably in response to overall economic conditions or credit tightening. During times of reduced market liquidity, the Fund may not be able to readily sell bonds at the prices at which they are carried on the Fund's books. If the Fund needed to sell large blocks of bonds to meet shareholder redemption requests or to raise cash, those sales could further reduce the bonds' prices.

Municipal Sector Concentration. While the Fund does not invest more than 25% of its total assets in a single industry, certain types of municipal securities (such as general obligation, government appropriation, municipal leases, special assessment and special tax bonds) are not considered a part of any "industry" for purposes of this policy. Therefore, the Fund may invest more than 25% of its total assets in these types of municipal securities. These types of municipal securities may finance, or pay interest from the revenues of, projects that tend to be impacted in the same way by economic, business or political developments which would increase credit risk. For example, legislation on the financing of a project or a declining economic need for the project would likely affect all similar projects.

Risks of Tobacco Related Bonds. In 1998, the largest U.S. tobacco manufacturers reached an out of court agreement, known as the Master Settlement Agreement (the "MSA"), to settle claims against them by 46 states and six other U.S. jurisdictions. The tobacco manufacturers agreed to make annual payments to the government entities in exchange for the release of all litigation claims. A number of the states have sold bonds that are backed by those future payments. The Fund may invest in two types of those bonds: (i) bonds that make payments only from a state's interest in the MSA and (ii) bonds that make payments from both the MSA revenue and from an "appropriation pledge" by the state. An "appropriation pledge" requires the state to pass a specific periodic appropriation to make the payments and is generally not an unconditional guarantee of payment by a state.

The settlement payments are based on factors, including, but not limited to, annual domestic cigarette shipments, cigarette consumption, inflation and the financial capability of participating tobacco companies. Payments could be reduced if consumption decreases, if market share is lost to non-MSA manufacturers, or if there is a negative outcome in litigation regarding the MSA, including challenges by participating tobacco manufacturers regarding the amount of annual payments owed under the MSA.

The Fund can invest up to 25% of its total assets in tobacco-related bonds without an appropriation pledge that make payments only from a state's interest in the MSA.

Main Risks of Borrowing and Leverage. The Fund can borrow up to one-third of the value of its total assets (including the amount borrowed) from banks, as permitted by the Investment Company Act of 1940. It can use those borrowings for a number of purposes, including for purchasing securities, which can create "leverage." In that case, changes in the value of the Fund's investments will have a larger effect on its share price than if it did not borrow. Borrowing results in interest payments to the lenders and related expenses. Borrowing for investment purposes might reduce the Fund's return if the yield on the securities purchased is less than those borrowing costs. The Fund may also borrow to meet redemption obligations, for temporary and emergency purposes, or to unwind or contribute to trusts in connection with the Fund's investment in inverse floaters. The Fund currently participates in a line of credit with other Oppenheimer funds for its borrowing.

The Fund can participate in a committed reverse repurchase agreement program. Reverse repurchase agreements that the Fund may engage in also create leverage. A reverse repurchase agreement is the sale by the Fund of a debt obligation to a party for a specified price, with the simultaneous agreement by the Fund to repurchase that debt obligation from that party on a future date at a higher price. Similar to a borrowing, reverse repurchase agreements provide the Fund with cash for investment and operational purposes. When the Fund engages in reverse repurchase agreements, changes in the value of the Fund's investments will have a larger effect on its share price than if it did not engage in these transactions due to the effect of leverage. Reverse repurchase agreements create fund expenses and require that the Fund have sufficient cash available to repurchase the debt obligation when required. Reverse repurchase agreements also involve the risk that the market value of the debt obligation that is the subject of the reverse repurchase agreement could decline significantly below the price at which the Fund is obligated to repurchase the security.

Risks of Derivatives. A "derivative" is an investment whose value depends on (or is derived from) the value of an underlying security, asset, interest rate, index or currency. Derivatives may be volatile and involve significant risks. Derivative transactions may require the payment of premiums and can increase portfolio turnover. Certain derivative investments may be illiquid. The underlying security or other reference on which a derivative is based, or the derivative itself, may not perform the way the Fund expects it to. The Fund could realize little or no income or lose principal from a derivative investment or a hedge might be unsuccessful. The Fund may also lose money if the issuer of a derivative fails to pay the amount due.

Inverse Floaters. The Fund invests in inverse floating rate securities ("inverse floaters") because, under ordinary circumstances, they offer higher yields and thus provide higher income than fixed-rate municipal bonds of comparable maturity and credit quality. Because inverse floaters are leveraged instruments, the value of an inverse floater will change more significantly in response to changes in interest rates and other market fluctuations than the market value of a conventional fixed-rate municipal security of similar maturity and credit quality, including the municipal bond underlying an inverse floater.

An inverse floater is created when a fixed-rate municipal bond is contributed to a trust. The trust issues two separate classes of securities: short-term floating rate securities with a fixed principal amount that represent a senior interest in the underlying municipal bond, and the inverse floater that represents a residual, subordinate interest in the underlying municipal bond. The trust issues and sells the short-term floating rate securities to third parties and the inverse floater to the Fund. The short-term floating rate securities generally bear short-term rates of interest. When interest is paid on the underlying municipal bond to the trust, such proceeds are first used to pay interest owing to holders of the short-term floating rate securities, with any remaining amounts being paid to the Fund, as the holder of the inverse floater. Accordingly, the amount of such interest paid to the Fund is inversely related to the rate of interest on the short-term floating rate securities. Inverse floaters produce less income when short-term interest rates rise (and, in extreme cases, may pay no income) and more income when short-term interest rates fall. Thus, if short-term interest rates rise after the issuance of the inverse floater, any yield advantage to the Fund is reduced and may be eliminated. Additionally, because the principal amount of the short-term floating rate security is fixed and is not adjusted in response to changes in the market value of the underlying municipal bond, any change in the market value of the underlying municipal bond is reflected entirely in a change to the value of the inverse floater. Upon the occurrence of certain adverse events, a trust may be collapsed and the underlying municipal bond liquidated, and the Fund could lose the entire amount of its investment in the inverse floater and may, in some cases, be contractually required to pay the negative difference, if any, between the liquidation value of the underlying municipal bond and the principal amount of the short-term floating rate securities.

The Fund may invest in inverse floaters with any degree of leverage (measured by the outstanding principal amount of related short-term floating rate securities). However, the Fund may only expose up to 20% of its total assets to the effects of leverage from its investments in inverse floaters. This limitation is measured by comparing the aggregate principal amount of the short-term floating rate securities that are related to the inverse floaters held by the Fund to the total assets of the Fund. Nevertheless, the value of, and income earned on, an inverse floater that has a higher degree of leverage (represented by a larger outstanding principal amount of related short-term floating rate securities) will fluctuate more significantly in response to changes in interest rates and to changes in the market value of the related underlying municipal bond, and are more likely to be eliminated entirely under adverse market conditions.

Who Is the Fund Designed For? The Fund is designed for investors seeking income exempt from federal, New York State and New York City personal income taxes in a municipal bond fund that focuses primarily on investment-grade obligations. The Fund does not seek capital appreciation. Investors should be willing to assume credit, interest rate and reinvestment risks. Because it invests in tax-exempt securities, the Fund is not appropriate for retirement plans or other tax-exempt or tax-deferred accounts or for investors whose primary goal is capital growth. The Fund is not a complete investment program. You should carefully consider your own investment goals and risk tolerance before investing in the Fund.

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.

Risk Lose Money [Text] rr_RiskLoseMoney The price of the Fund's shares can go up and down substantially. The value of the Fund's investments may change because of broad changes in the markets in which the Fund invests or because of poor investment selection, which could cause the Fund to underperform other funds with similar investment objectives. There is no assurance that the Fund will achieve its investment objective. When you redeem your shares, they may be worth more or less than what you paid for them. These risks mean that you can 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 how the Fund's average annual returns for 1, 5 and 10 years compare with those of a broad measure of market performance. The Fund's past investment performance (before and after taxes) 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: https://www.oppenheimerfunds.com/fund/RochesterFundMunicipals

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

Sales charges and taxes are not included and the returns would be lower if they were. During the period shown, the highest return for a calendar quarter was 20.68% (3rd Qtr 09) and the lowest return was -20.59% (4th Qtr 08).
Performance Table Heading rr_PerformanceTableHeading

Average Annual Total Returns for the periods ended December 31, 2011
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the highest individual federal marginal income tax rates and do not reflect the impact of state or local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Your actual after-tax returns, depending on your individual tax situation, may differ from those shown and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for only one class and after-tax returns for other classes will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

The following table shows the average annual total returns for each class of the Fund's shares. After-tax returns are calculated using the highest individual federal marginal income tax rates and do not reflect the impact of state or local taxes. Your actual after-tax returns, depending on your individual tax situation, may differ from those shown and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for only one class and after-tax returns for other classes will vary.
(Oppenheimer Rochester® Fund Municipals) | Barclays Capital Municipal Bond Index
  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 10.70%
5 Years rr_AverageAnnualReturnYear05 5.22%
10 Years rr_AverageAnnualReturnYear10 5.38%
(Oppenheimer Rochester® Fund Municipals) | Consumer Price Index
  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 2.96%
5 Years rr_AverageAnnualReturnYear05 2.26%
10 Years rr_AverageAnnualReturnYear10 2.48%
(Oppenheimer Rochester® Fund Municipals) | Class A
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) imposed on purchases (as % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 4.75%
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees rr_ManagementFeesOverAssets 0.46%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Interest and Fees from Borrowings rr_Component1OtherExpensesOverAssets 0.06%
Interest and Related Expenses from Inverse Floaters rr_Component2OtherExpensesOverAssets 0.15%
Other Expenses rr_Component3OtherExpensesOverAssets 0.08%
Total Other Expenses rr_OtherExpensesOverAssets 0.29%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.90%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 563
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 750
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 952
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,535
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 563
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 750
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 952
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 1,535
Annual Return 2002 rr_AnnualReturn2002 5.46%
Annual Return 2003 rr_AnnualReturn2003 8.12%
Annual Return 2004 rr_AnnualReturn2004 7.25%
Annual Return 2005 rr_AnnualReturn2005 8.76%
Annual Return 2006 rr_AnnualReturn2006 8.33%
Annual Return 2007 rr_AnnualReturn2007 (1.59%)
Annual Return 2008 rr_AnnualReturn2008 (30.84%)
Annual Return 2009 rr_AnnualReturn2009 45.07%
Annual Return 2010 rr_AnnualReturn2010 3.63%
Annual Return 2011 rr_AnnualReturn2011 11.50%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest return for a calendar quarter was 20.68% (3rd Qtr 09)
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 20.68%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest return was -20.59% (4th Qtr 08)
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (20.59%)
1 Year rr_AverageAnnualReturnYear01 6.21%
5 Years rr_AverageAnnualReturnYear05 1.68%
10 Years rr_AverageAnnualReturnYear10 4.59%
Inception Date rr_AverageAnnualReturnInceptionDate May 15, 1986
(Oppenheimer Rochester® Fund Municipals) | Class A | Return After Taxes on Distributions
  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 6.21%
5 Years rr_AverageAnnualReturnYear05 1.68%
10 Years rr_AverageAnnualReturnYear10 4.59%
(Oppenheimer Rochester® Fund Municipals) | Class A | Return After Taxes on Distributions and Sale of Fund Shares
  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 6.35%
5 Years rr_AverageAnnualReturnYear05 2.19%
10 Years rr_AverageAnnualReturnYear10 4.74%
(Oppenheimer Rochester® Fund Municipals) | Class B
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) imposed on purchases (as % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice 5.00%
Management Fees rr_ManagementFeesOverAssets 0.46%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Interest and Fees from Borrowings rr_Component1OtherExpensesOverAssets 0.06%
Interest and Related Expenses from Inverse Floaters rr_Component2OtherExpensesOverAssets 0.15%
Other Expenses rr_Component3OtherExpensesOverAssets 0.19%
Total Other Expenses rr_OtherExpensesOverAssets 0.40%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.86%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 691
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 890
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,215
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,710
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 191
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 590
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,015
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 1,710
1 Year rr_AverageAnnualReturnYear01 5.47%
5 Years rr_AverageAnnualReturnYear05 1.41%
10 Years rr_AverageAnnualReturnYear10 4.55%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 17, 1997
(Oppenheimer Rochester® Fund Municipals) | Class C
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) imposed on purchases (as % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees rr_ManagementFeesOverAssets 0.46%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Interest and Fees from Borrowings rr_Component1OtherExpensesOverAssets 0.06%
Interest and Related Expenses from Inverse Floaters rr_Component2OtherExpensesOverAssets 0.15%
Other Expenses rr_Component3OtherExpensesOverAssets 0.11%
Total Other Expenses rr_OtherExpensesOverAssets 0.32%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 1.78%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 282
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 565
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 973
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,113
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 182
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 565
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 973
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 2,113
1 Year rr_AverageAnnualReturnYear01 9.56%
5 Years rr_AverageAnnualReturnYear05 1.79%
10 Years rr_AverageAnnualReturnYear10 4.19%
Inception Date rr_AverageAnnualReturnInceptionDate Mar. 17, 1997
(Oppenheimer Rochester® Fund Municipals) | Class Y
  
Risk/Return: rr_RiskReturnAbstract  
Maximum Sales Charge (Load) imposed on purchases (as % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (Load) (as % of the lower of the original offering price or redemption proceeds) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Management Fees rr_ManagementFeesOverAssets 0.46%
Distribution and/or Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Interest and Fees from Borrowings rr_Component1OtherExpensesOverAssets 0.06%
Interest and Related Expenses from Inverse Floaters rr_Component2OtherExpensesOverAssets 0.15%
Other Expenses rr_Component3OtherExpensesOverAssets 0.10%
Total Other Expenses rr_OtherExpensesOverAssets 0.31%
Total Annual Fund Operating Expenses rr_ExpensesOverAssets 0.77%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 79
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 247
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 429
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 958
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 79
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 247
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 429
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 958
1 Year rr_AverageAnnualReturnYear01 11.64%
5 Years rr_AverageAnnualReturnYear05 2.82%
10 Years rr_AverageAnnualReturnYear10 5.24%
Inception Date rr_AverageAnnualReturnInceptionDate Apr. 28, 2000