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Label Element Value
Prospectus: rr_ProspectusTable  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Dec. 31, 2018
Entity Registrant Name dei_EntityRegistrantName RYDEX SERIES FUNDS
Central Index Key dei_EntityCentralIndexKey 0000899148
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate May 01, 2019
Document Effective Date dei_DocumentEffectiveDate May 01, 2019
Prospectus Date rr_ProspectusDate May 01, 2019
RYDEX SERIES FUNDS CLASS H | Commodities Strategy Fund  
Prospectus: rr_ProspectusTable  
Risk/Return [Heading] rr_RiskReturnHeading COMMODITIES STRATEGY FUND
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Commodities Strategy Fund (the “Fund”) seeks to provide investment results that correlate, before fees and expenses, to the performance of a benchmark for commodities. The Fund’s current benchmark is the S&P GSCI® Commodity Index (the “underlying index”).
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy and hold Class H shares of the Fund.
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)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination The Advisor has contractually agreed to waive the management fee it receives from the Fund in an amount equal to the management fee paid to the Advisor by the Subsidiary. This undertaking will continue in effect for so long as the Fund invests in the Subsidiary, and may be terminated only with the approval of the Fund’s Board of Trustees.
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 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 Total Annual Fund Operating Expenses or the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 65% of the average value of its portfolio. The Fund’s portfolio turnover rate is calculated without regard to cash instruments and most derivatives. If such instruments were included, the Fund’s portfolio turnover rate might be significantly higher.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 65.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Fee Waiver in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.
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.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption The Example assumes 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. 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 costs would be:
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund seeks exposure to the performance of the commodities markets. The Fund will seek to gain exposure to the underlying index, a composite index of commodity sector returns, representing an unleveraged long-only investment in commodity futures that is broadly diversified across the spectrum of commodities, by investing in exchange-traded products, including investment companies and commodity pools, that provide exposure to the commodities markets and in commodity-linked derivative instruments, which primarily consist of swap agreements, commodity options, and futures and options on futures. While the Fund may write (sell) and purchase swaps, it expects primarily to purchase swaps. Investing in derivative instruments enables the Fund to pursue its objective without investing directly in physical commodities. Certain of the Fund’s derivatives investments may be traded in the over-the-counter (“OTC”) market. Investments in derivative instruments, such as futures, options, and forward contracts and swap agreements, have the economic effect of creating financial leverage in the Fund’s portfolio because such investments may give rise to losses that exceed the amount the Fund has invested in those instruments. Financial leverage will magnify, sometimes significantly, the Fund’s exposure to any increase or decrease in prices associated with a particular reference asset resulting in increased volatility in the value of the Fund’s portfolio. The value of the Fund’s portfolio is likely to experience greater volatility over short-term periods. While such financial leverage has the potential to produce greater gains, it also may result in greater losses, which in some cases may cause the Fund to liquidate other portfolio investments at a loss to comply with limits on leverage and asset segregation requirements imposed by the Investment Company Act of 1940 (the “1940 Act”) or to meet redemption requests. The Fund’s use of derivatives and the leveraged investment exposure created by the use of derivatives are expected to be significant. To the extent the underlying index is concentrated in a particular industry the Fund will necessarily be concentrated in that industry. It is anticipated that the Fund’s investment exposure will tend to be heavily weighted toward oil and other energy-related commodities. On a day-to-day basis, the Fund may hold U.S. government securities or cash equivalents to collateralize its derivatives positions. The Fund also may enter into repurchase agreements with counterparties that are deemed to present acceptable credit risks.

The Fund may invest a portion of its assets, and at times, a substantial portion of its assets, in other short-term fixed-income investment companies advised by the Advisor, or an affiliate of the Advisor, for various purposes, including for liquidity management purposes (e.g., to increase yield on liquid investments used to collateralize derivatives positions) or when such investment companies present a more cost-effective investment option than direct investments in the underlying securities. Investments in these investment companies will significantly increase the portfolio’s exposure to certain other asset categories, including: (i) a broad range of high yield, high risk debt securities rated below the top four long-term rating categories by a nationally recognized statistical rating organization or, if unrated, determined by the Advisor to be of comparable quality (also known as “junk bonds”); (ii) securities issued by the U.S. government or its agencies and instrumentalities; (iii) collateralized loan obligations (“CLOs”), other asset-backed securities (including mortgage-backed securities) and similarly structured debt investments; and (iv) other short-term fixed income securities. Such investments will expose the Fund to the risks of these asset categories and increases or decreases in the value of these investments may cause the Fund to deviate from its investment objective.

The Fund also may invest up to 25% of its total assets in a wholly-owned and controlled Cayman Islands subsidiary (the “Subsidiary”) as measured at the end of every quarter of the Fund's taxable year. The Subsidiary is advised by the Advisor, and has the same investment objective as the Fund. Unlike the Fund, however, the Subsidiary may invest to a greater extent in commodity-linked derivative instruments. The Subsidiary’s investments in such instruments are subject to limits on leverage imposed by the 1940 Act. The Fund’s investment in the Subsidiary is expected to provide the Fund with an effective means of obtaining exposure (long or short) to the investment returns of global commodities markets.
In an effort to ensure that the Fund is fully invested on a day-to-day basis, the Fund may conduct any necessary trading activity at or just prior to the close of the U.S. financial markets. The Fund invests, to a significant extent, in companies or commodity-linked derivatives concentrated in the same economic sector. The Fund is non-diversified and, therefore, may invest a greater percentage of its assets in a particular issuer in comparison to a diversified fund.
Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with all mutual funds, a shareholder is subject to the risk that his or her investment could lose money. In addition to this risk, the Fund is subject to the principal risks described below.

ASSET-BACKED AND MORTGAGE-BACKED SECURITIES RISK—Through its investments in other investment companies, the Fund may have exposure to asset-backed securities, including mortgage-backed securities and structured finance investments. Investors in these securities generally receive payments that are part interest and part return of principal. These payments may vary based on the rate at which the underlying borrowers pay off their loans. Some asset-backed securities, including mortgage-backed securities, may have structures that make their reaction to interest rates and other factors difficult to predict, making their prices very volatile and they are subject to liquidity risk.

CLO RISK—Through its investments in other investment companies, the Fund may have exposure to CLOs. A CLO is a trust typically collateralized by a pool of loans, which may include, among others, domestic and foreign senior secured loans, senior unsecured loans, and subordinate corporate loans, including loans that may be rated below investment grade or equivalent unrated loans. The cash flows from the trust are split into two or more portions, called tranches, varying in risk and yield. CLO tranches can experience substantial losses due to actual defaults, increased sensitivity to defaults due to collateral default and disappearance of protecting tranches, market anticipation of defaults, as well as aversion to CLO securities as a class. The risks of an investment in a CLO depend largely on the type of the collateral securities and the class of the CLO in which the Fund invests.

COMMODITY EXPOSURE RISK—The Fund will concentrate its investments in commodities markets and will therefore have investment exposure to the commodities markets and one or more sectors of the commodities markets, which may subject the Fund to greater volatility than investments in traditional securities, such as stocks and bonds. Volatility in the commodities markets may be caused by changes in overall market movements, commodity index volatility, domestic and foreign political and economic events and policies, war, acts of terrorism, changes in domestic or foreign interest rates and/or investor expectations concerning interest rates, domestic and foreign inflation rates, investment and trading activities of mutual funds, hedge funds and commodities funds, and factors affecting a particular industry or commodity, such as drought, floods, weather, livestock disease, embargoes, tariffs and other regulatory developments, or supply and demand disruptions. The prices of energy, industrial metals, precious metals, agriculture and livestock sector commodities may fluctuate widely due to factors such as changes in value, supply and demand and governmental regulatory policies. Because the Fund’s performance is linked to the performance of volatile commodities, investors should be willing to assume the risks of potentially significant fluctuations in the value of the Fund’s shares. 

COMMODITY-LINKED DERIVATIVES INVESTMENT RISK—The Fund may invest directly and indirectly in commodity-linked derivative instruments. The value of a commodity-linked derivatives investment typically is based upon the price movements of a physical commodity (such as heating oil, livestock, or agricultural products), a commodity futures contract or commodity index, or some other readily measurable economic variable dependent upon changes in the value of commodities or the commodities markets. The value of these securities will rise or fall in response to changes in the underlying commodity or related benchmark or investment. These securities expose the Fund economically to movements in commodity prices. The Fund’s investment in commodity-related investment products may lead to losses in excess of the Fund’s investment in such products. Such losses can significantly and adversely affect the net asset value ("NAV") of the Fund and, consequently, a shareholder’s interest in the Fund.

COUNTERPARTY CREDIT RISK—The Fund may invest in financial instruments involving counterparties that attempt to gain exposure to a particular group of securities, index or asset class without actually purchasing those securities or investments, or to hedge a position. The Fund’s use of such financial instruments, including swap agreements, involves risks that are different from those associated with ordinary portfolio securities transactions. For example, the Fund is exposed to the risk that the counterparty may be unwilling or unable to make timely payments to meet its contractual obligations or may fail to return holdings that are subject to the agreement with the counterparty. If the counterparty becomes bankrupt or defaults on its payment obligations to the Fund, the Fund may not receive the full amount that it is entitled to receive. If this occurs, the value of your shares in the Fund will decrease.

CREDIT RISK—The Fund could lose money if the debt securities or other instruments in which it invests decline in price, or the issuer or guarantor of such instrument fails to pay interest or principal when due because the issuer or guarantor of the instrument experiences an actual or perceived decline in its financial status. Generally, credit risk is increased when a portfolio security is downgraded or the perceived creditworthiness of the issuer or guarantor deteriorates, though the effect of any credit rating downgrade can be uncertain. To the extent the Fund invests in below investment grade instruments, it will be exposed to a greater amount of credit risk than a fund which only invests in investment grade securities. In addition, to the extent the Fund uses credit derivatives, such use will expose it to additional risk in the event that the bonds underlying the derivatives default. The degree of credit risk depends on the issuer’s or guarantor’s financial condition and on the terms of the instruments.

DERIVATIVES RISK—The Fund’s investments in derivatives may pose risks in addition to and greater than those associated with investing directly in securities or other investments, including risks relating to leverage, imperfect correlations with underlying investments or the Fund’s other portfolio holdings, high price volatility, lack of availability, counterparty credit, liquidity, valuation and legal restrictions. Their use is a highly specialized activity that involves investment techniques and risks different from those associated with ordinary portfolio securities transactions. If the Advisor is incorrect about its expectations of market conditions, the use of derivatives could also result in a loss, which in some cases may be unlimited. Certain risks are specific to the derivatives in which the Fund invests.

SWAP AGREEMENTS RISK—Swap agreements are contracts among the Fund and a counterparty to exchange the return of the pre-determined underlying investment (such as the rate of return of the underlying index). Swap agreements may be negotiated bilaterally and traded OTC between two parties or, in some instances, must be transacted through a futures commission merchant and cleared through a clearinghouse that serves as a central counterparty. Risks associated with the use of swap agreements are different from those associated with ordinary portfolio securities transactions, due in part to the fact they could be considered illiquid and many swaps trade on the OTC market. Swaps are particularly subject to counterparty credit, correlation, valuation, liquidity and leveraging risks. Certain standardized swaps are subject to mandatory central clearing. Central clearing is expected to reduce counterparty credit risk and increase liquidity, but central clearing does not make swap transactions risk-free.

FUTURES CONTRACTS RISK—Futures contracts are typically exchange-traded contracts that call for the future delivery of an asset at a certain price and date, or cash settlement of the terms of the contract. Risks of futures contracts may be caused by an imperfect correlation between movements in the price of the instruments and the price of the underlying securities. In addition, there is the risk that the Fund may not be able to enter into a closing transaction because of an illiquid market. Exchanges can limit the number of positions that can be held or controlled by the Fund or the Advisor, thus limiting the ability to implement the Fund’s strategies. Futures markets are highly volatile and the use of futures may increase the volatility of the Fund’s NAV. Futures also are subject to leverage risks and to liquidity risk.

OPTIONS CONTRACTS RISK—Options or options on futures contracts give the holder of the option the right to buy (or to sell) a position in a security or in a contract to the writer of the option, at a certain price. They are subject to correlation risk because there may be an imperfect correlation between the options and the securities markets that cause a given transaction to fail to achieve its objectives. The successful use of options depends on the Advisor’s ability to correctly predict future price fluctuations and the degree of correlation between the options and securities markets. Exchanges can limit the number of positions that can be held or controlled by the Fund or the Advisor, thus limiting the ability to implement the Fund’s strategies. Options also are particularly subject to leverage risk and can be subject to liquidity risk.

EARLY CLOSING RISK—The Fund is subject to the risk that unanticipated early closings of securities exchanges and other financial markets may result in the Fund’s inability to buy or sell securities or other financial instruments on that day and may cause the Fund to incur substantial trading losses.

EQUITY RISK—The Fund is subject to the risk that the value of the equity securities and equity-based derivatives in the Fund’s portfolio will decline due to volatility in the equity market caused by general market and economic conditions, perceptions regarding particular industries represented in the equity market, or factors relating to specific companies to which the Fund has investment exposure.

FINANCIALS SECTOR RISK—The Fund's investments are exposed to issuers conducting business in the Financials Sector. The Financials Sector includes companies involved in banking, thrifts and mortgage finance, specialized finance, consumer finance, asset management and custody banks, investment banking and brokerage and insurance. It also includes the Financial Exchanges & Data and Mortgage Real Estate Investment Trusts ("REITs") sub-industries. Certain financial sector companies serve as counterparties with which the Fund may enter into derivatives agreements or other similar contractual arrangements. The Fund is subject to the risk that the securities of such issuers will underperform the market as a whole due to legislative or regulatory changes, adverse market conditions and/or increased competition affecting the Financials Sector, which may adversely affect a company's ability to fulfill its obligations as a financial counterparty. Companies operating in the Financials Sector are subject to extensive government regulation, which may limit the financial commitments they can make and the interest rates and fees they can charge. Profitability is largely dependent on the availability and cost of capital funds, and can fluctuate significantly when interest rates change or due to increased competition.

HIGH YIELD AND UNRATED SECURITIES RISK—The Fund’s exposure to higher yielding, below investment grade and unrated high risk debt securities (commonly known as “junk bonds”) may present additional risk because these securities may be less liquid and present greater credit risk than investment grade bonds. The price of high yield securities tends to be subject to greater volatility due to issuer-specific operating results and outlook and to real or perceived adverse economic and competitive industry conditions. This exposure may be obtained through investments in other investment companies.

INTEREST RATE RISK—The market value of fixed income investments and related financial instruments will change in response to interest rate changes. During periods of falling interest rates, the values of fixed income securities generally rise. Conversely, during periods of rising interest rates, the values of such securities generally decline. Securities with greater interest rate sensitivity and longer maturities generally are subject to greater fluctuations in value. The Fund may invest in variable and floating rate securities. Although these instruments are generally less sensitive to interest rate changes than fixed rate instruments, the value of floating rate and variable securities may decline if their interest rates do not rise as quickly, or as much, as general interest rates. Changes in government or central bank policy, including changes in tax policy or changes in a central bank’s implementation of specific policy goals, may have a substantial impact on interest rates, and could have an adverse effect on prices for fixed income securities and on the performance of the Fund. There can be no guarantee that any particular government or central bank policy will be continued, discontinued or changed, nor that any such policy will have the desired effect on interest rates.

INVESTMENT IN INVESTMENT VEHICLES RISK—Investing in other investment vehicles, including exchange-traded funds (“ETFs”), closed-end funds, affiliated short-term fixed income funds and other mutual funds, subjects the Fund to those risks affecting the investment vehicle, including the possibility that the value of the underlying securities held by the investment vehicle could decrease or the portfolio becomes illiquid. Moreover, the Fund and its shareholders will incur its pro rata share of the underlying vehicles’ expenses, which will reduce the Fund’s performance. In addition, investments in an ETF are subject to, among other risks, the risk that the ETF’s shares may trade at a discount or premium relative to the net asset value of the shares and the listing exchange may halt trading of the ETF’s shares.

INVESTMENT IN LOANS RISK—Investing in loans involves special types of risks, including credit risk, interest rate risk, counterparty risk and prepayment risk. Loans may offer a fixed or floating interest rate. Loans are often generally below investment grade and may be unrated. Loans may be difficult to value and some can be subject to liquidity risk.

INVESTMENT IN THE SUBSIDIARY RISK—The Subsidiary is not registered under the 1940 Act and, unless otherwise noted in this Prospectus, is not subject to all of the investor protections of the 1940 Act. Thus, the Fund, as the sole investor in the Subsidiary, will not have all of the protections offered to shareholders of registered investment companies. By investing in the Subsidiary, the Fund is exposed to the risks of the Subsidiary’s investments, which in turn will be exposed primarily to the risks of investing in the commodities markets. The Fund also will incur its pro rata share of the expenses of the Subsidiary. In addition, changes in the laws of the United States or the Cayman Islands, under which the Fund and the Subsidiary, respectively, are organized, could result in the inability of the Fund and/or the Subsidiary to operate as intended and could negatively affect the Fund and its shareholders.

INVESTMENT TECHNIQUE RISK—Some investment techniques of the Fund, such as its use of derivatives and other commodity-linked financial instruments to seek to achieve its investment objective, may be considered aggressive.  These instruments may increase the volatility of the Fund and may involve a small investment of cash relative to the magnitude of the risk assumed. Such investment techniques may not consistently produce desired results and may be limited by legislative, regulatory, or tax developments.

LEVERAGING RISK—The Fund derives substantially all of its commodities exposure from its investment in derivatives and other financial instruments that provide leveraged exposure. The Fund’s investment in these instruments generally requires a small investment relative to the amount of investment exposure assumed. As a result, such investments may give rise to losses that exceed the amount invested in those instruments. The use of derivatives and other similar financial instruments are an integral part of the Fund’s investment strategy and may expose the Fund to potentially dramatic losses (or gains) in the value of a derivative or other financial instrument and, thus, in the value of the Fund’s portfolio. The cost of investing in such instruments generally increases as interest rates increase, which will lower the Fund’s return.

LIQUIDITY AND VALUATION RISK—In certain circumstances, it may be difficult for the Fund to purchase and sell a particular investment within a reasonable time at a fair price, or the price at which it has been valued by the Advisor for purposes of the Fund's NAV, causing the Fund to be less liquid. While the Fund intends to invest in liquid securities and financial instruments, under certain market conditions, such as when trading in a particular investment has been halted temporarily by an exchange because the maximum price change of that investment has been realized, it may be difficult or impossible for the Fund to liquidate such investments. In addition, the ability of the Fund to assign an accurate daily value to certain investments may be difficult, and the Advisor may be required to fair value the investments.

MARKET RISK—The market value of the securities and derivatives held by the Fund may fluctuate over time in response to factors affecting individual companies or other factors such as changing economic, political or financial markets.

NON-DIVERSIFICATION RISK—The Fund is considered non-diversified and can invest a greater portion of its assets in securities of individual issuers than a diversified fund. As a result, changes in the market value of a single issuer's securities could cause greater fluctuations in the value of Fund shares than would occur in a diversified fund.

OTC TRADING RISK—Certain of the derivatives in which the Fund may invest may be traded (and privately negotiated) in the OTC market. While the OTC derivatives market is the primary trading venue for many derivatives, it is largely unregulated and provides for less transparency than a national securities or commodities exchange. As a result and similar to other privately negotiated contracts, the Fund is subject to counterparty credit risk with respect to such derivatives contracts.

PASSIVE INVESTMENT RISK—The Fund is not actively managed and the Advisor does not attempt to take defensive positions in declining markets. Therefore, the Fund may be subject to greater losses in a declining market than a fund that is actively managed.

PORTFOLIO TURNOVER RISK—The Fund’s strategy may frequently involve buying and selling portfolio securities, which may lead to increased costs to the Fund. Portfolio turnover risk may cause the Fund’s performance to be less than you expect.

PREPAYMENT AND EXTENSION RISK—Prepayment risk is the risk that the principal on mortgage-backed securities, other asset-backed securities or any debt security with an embedded call option may be prepaid at any time, which could reduce the security’s yield and market value. In the case of prepayment risk, if the investment is converted, prepaid or redeemed before maturity, the portfolio manager may not be able to invest the proceeds in other investments providing as high a level of income, resulting in a reduced yield to the Fund. The rate of prepayments tends to increase as interest rates fall, which could cause the average maturity of the portfolio to shorten. Conversely, extension risk is the risk that an unexpected rise in interest rates will extend the life of a mortgage- or asset-backed security beyond the prepayment time. If the Fund’s investments are locked in at a lower interest rate for a longer period of time, the portfolio manager may be unable to capitalize on securities with higher interest rates or wider spreads.

REPURCHASE AGREEMENT RISK—The Fund’s investment in repurchase agreements may be subject to market and credit risk with respect to the collateral securing the repurchase agreements. Investments in repurchase agreements also may be subject to the risk that the market value of the underlying obligations may decline prior to the expiration of the repurchase agreement term.

SHAREHOLDER TRADING RISK—The Fund may be used as a tool for certain investors that employ trading strategies involving frequent trading. Such trading strategies may lead to increased portfolio turnover in the Fund, higher transaction costs, and the possibility of increased short-term capital gains (which will be taxable to shareholders as ordinary income when distributed to them) and/or long-term capital gains. Large movements of assets into and out of the Fund due to active or frequent trading also may adversely affect the Fund's ability to achieve its investment objective.

TAX RISK—To qualify for the favorable U.S. federal income tax treatment generally available to regulated investment companies, the Fund must derive at least 90% of its gross income for each taxable year from sources generating “qualifying income.” Income derived from direct and certain indirect investments in commodities is not qualifying income. More information about this requirement can be found in the SAI. The Fund’s investment in the Subsidiary is expected to provide the Fund with exposure to the commodities markets within the limitations of the federal tax requirements of Subchapter M of the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”). The Fund has received a private letter ruling from the Internal Revenue Service that concluded that the income attributable to the Fund's investment in the Subsidiary will be qualifying income. The Internal Revenue Service has recently issued final regulations pursuant to which the “Subpart F” income (as defined in Section 951 of the Internal Revenue Code to include passive income, including income from commodity-linked derivatives) of the Fund attributable to its investment in the Subsidiary is “qualifying income” to the Fund to the extent that such income is derived with respect to the Fund’s business of investing in stock, securities or currencies. The Fund expects its “Subpart F” income attributable to its investment in the Subsidiary to be derived with respect to the Fund’s business of investing in stock, securities or currencies. Such final regulations do not adopt the requirement of the proposed regulations issued by the Internal Revenue Service in September 2016 that would have generally required the Subsidiary to distribute its income (i.e., the “Subpart F” income of the Fund attributable to its investment in the Subsidiary) each year in order for the Fund to treat that income as “qualifying income.” The Fund may rely on such final regulations for taxable years beginning after the issuance of such proposed regulations on September 28, 2016. Accordingly, the Fund expects its “Subpart F” income attributable to its investment in the Subsidiary to be treated as “qualifying income.” The Advisor intends to conduct the Fund’s investments in the Subsidiary in a manner consistent with the terms and conditions of its private letter ruling and applicable Internal Revenue Code regulations, and will monitor the Fund's investments in the Subsidiary to ensure that no more than 25% of the Fund’s assets are invested in the Subsidiary.

The Fund currently gains most of its exposure to the commodities markets through its investment in the Subsidiary, which may invest in commodity-linked derivative instruments and other similar instruments. However, to the extent the Fund invests in such instruments directly, it may be subject to the risk that such instruments will not generate qualifying income and, thus, may compromise the Fund’s ability to qualify as a regulated investment company. The Fund might generate more non-qualifying income than anticipated, might not be able to generate qualifying income in a particular taxable year at levels sufficient to meet the qualifying income test, or might not be able to determine the percentage of qualifying income it derives for a taxable year until after year-end. Failure to comply with the qualifying income test would have significant negative tax consequences to Fund shareholders. Under certain circumstances, the Fund may be able to cure a failure to meet the qualifying income test, but in order to do so the Fund may incur significant Fund-level taxes, which would effectively reduce (and could eliminate) the Fund’s returns.

TEMPORARY DEFENSIVE INVESTMENT RISK—The Advisor generally does not attempt to take defensive positions in the Fund in declining markets. Therefore, the Fund may be subject to greater losses in a declining market than a fund that does take defensive positions in declining markets.

TRACKING ERROR RISK—The Advisor may not be able to cause the Fund’s performance to correlate to that of the Fund’s benchmark, either on a daily or aggregate basis. Factors such as Fund expenses, imperfect correlation between the Fund’s investments and those of the underlying index, rounding of share prices, changes to the composition of the underlying index, regulatory policies, high portfolio turnover rate and the use of leverage all contribute to tracking error. Tracking error may cause the Fund’s performance to be less than you expect.

TRADING HALT RISK—The Fund typically will hold futures contracts and short-term options. The major exchanges on which these contracts are traded, such as the Chicago Mercantile Exchange, have established limits on how much the trading price of a futures contract or option may decline over various time periods within a day, and may halt trading in a contract that exceeds such limits. If a trading halt occurs, the Fund may temporarily be unable to purchase or sell certain securities, futures contracts or options. Such a trading halt near the time the Fund prices its shares may prevent the Fund from achieving its investment objective.
Risk Lose Money [Text] rr_RiskLoseMoney As with all mutual funds, a shareholder is subject to the risk that his or her investment could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is considered non-diversified and can invest a greater portion of its assets in securities of individual issuers than a diversified fund. As a result, changes in the market value of a single issuer's securities could cause greater fluctuations in the value of Fund shares than would occur in a diversified fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PERFORMANCE INFORMATION
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart shows the performance of the Class H shares of the Fund from year to year. The variability of performance over time provides an indication of the risks of investing in the Fund. The following table shows the performance of the Class H shares of the Fund as an average over different periods of time in comparison to the performance of a broad-based market index. The figures in the bar chart and table assume the reinvestment of dividends and capital gains distributions. Of course, this past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.
Updated performance information is available on the Fund’s website at www.guggenheiminvestments.com or by calling 800.820.0888.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart shows the performance of the Class H shares of the Fund from year to year. The variability of performance over time provides an indication of the risks of investing in the Fund. The following table shows the performance of the Class H shares of the Fund as an average over different periods of time in comparison to the performance of a broad-based market index.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 800.820.0888
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.guggenheiminvestments.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Of course, this past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Highest Quarter Return
 
Lowest Quarter Return
Q2 2009
20.44%
 
Q4 2014
-27.65%
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURN (for periods ended December 31, 2018)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate The after-tax returns presented in the table below are calculated using highest historical individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Your actual after-tax returns will depend on your specific tax situation and may differ from those shown below. After-tax returns are not relevant to investors who hold shares of the Fund through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
The after-tax returns presented in the table below are calculated using highest historical individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your specific tax situation and may differ from those shown below. After-tax returns are not relevant to investors who hold shares of the Fund through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
RYDEX SERIES FUNDS CLASS H | Commodities Strategy Fund | Class H  
Prospectus: rr_ProspectusTable  
Trading Symbol dei_TradingSymbol RYMBX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.88%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.57%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.11%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.68% [1]
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.82% [2]
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [3]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.69% [2]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 172
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 533
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 918
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,998
Annual Return 2009 rr_AnnualReturn2009 7.09%
Annual Return 2010 rr_AnnualReturn2010 5.74%
Annual Return 2011 rr_AnnualReturn2011 (3.67%)
Annual Return 2012 rr_AnnualReturn2012 (1.57%)
Annual Return 2013 rr_AnnualReturn2013 (3.55%)
Annual Return 2014 rr_AnnualReturn2014 (33.85%)
Annual Return 2015 rr_AnnualReturn2015 (34.58%)
Annual Return 2016 rr_AnnualReturn2016 10.52%
Annual Return 2017 rr_AnnualReturn2017 4.65%
Annual Return 2018 rr_AnnualReturn2018 (15.50%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 20.44%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2014
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (27.65%)
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (15.50%)
5 Years rr_AverageAnnualReturnYear05 (15.81%)
10 Years rr_AverageAnnualReturnYear10 (7.92%)
RYDEX SERIES FUNDS CLASS H | Commodities Strategy Fund | Class H | After Taxes on Distributions  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (25.37%)
5 Years rr_AverageAnnualReturnYear05 (17.99%)
10 Years rr_AverageAnnualReturnYear10 (9.33%)
RYDEX SERIES FUNDS CLASS H | Commodities Strategy Fund | Class H | After Taxes on Distributions and Sales  
Prospectus: rr_ProspectusTable  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (8.58%)
5 Years rr_AverageAnnualReturnYear05 (11.54%)
10 Years rr_AverageAnnualReturnYear10 (5.70%)
RYDEX SERIES FUNDS CLASS H | Commodities Strategy Fund | Class H | S&P GSCI Commodity Index  
Prospectus: rr_ProspectusTable  
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes reflects no deduction for fees, expenses or taxes
Label rr_AverageAnnualReturnLabel S&P GSCI® Commodity Index (reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (13.82%)
5 Years rr_AverageAnnualReturnYear05 (14.52%)
10 Years rr_AverageAnnualReturnYear10 (5.78%)
[1] "Other Expenses” does not include fees paid to the Fund’s swap contract counterparties, or the management fees, performance fees, and expenses of the reference assets or trading vehicles underlying such swap contracts. These fees and expenses, which are not reflected in this Annual Fund Operating Expenses table, are embedded in the returns of the swap contracts (i.e., the fees and expenses reduce the investment return of the swap contracts) and represent an indirect cost of investing in the Fund.
[2] The Total Annual Fund Operating Expenses and Total Annual Fund Operating Expenses After Fee Waiver in this fee table may not correlate to the expense ratios in the Fund’s financial highlights and financial statements because the financial highlights and financial statements reflect only the operating expenses of the Fund and do not include Acquired Fund Fees and Expenses, which are fees and expenses incurred indirectly by the Fund through its investments in certain underlying investment companies.
[3] The Advisor has contractually agreed to waive the management fee it receives from the Fund in an amount equal to the management fee paid to the Advisor by the Subsidiary. This undertaking will continue in effect for so long as the Fund invests in the Subsidiary, and may be terminated only with the approval of the Fund’s Board of Trustees.