v3.26.3
State Street DoubleLine Short Duration Total Return Tactical ETF Investment Risks - State Street DoubleLine Short Duration Total Return Tactical ETF
Jun. 30, 2026
Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Market Risk: The Fund's investments are subject to changes in general economic conditions, general market fluctuations and the risks inherent in investment in securities markets. Investment markets can be volatile and prices of investments can change substantially due to various factors including, but not limited to, economic growth or recession, changes in interest rates, inflation, changes in the actual or perceived creditworthiness of issuers, and general market liquidity. The Fund is subject to the risk that geopolitical events will disrupt securities markets and adversely affect global economies and markets. Local, regional or global events such as war, military conflicts, acts of terrorism, trade policy changes or disputes, the threat or actual imposition of tariffs, natural disasters, the spread of infectious illness or other public health issues, or other events could have a significant impact on the Fund and its investments.
Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Debt Securities Risk: The values of debt securities may increase or decrease as a result of the following: market fluctuations, changes in interest rates, actual or perceived inability or unwillingness of issuers, guarantors or liquidity providers to make scheduled principal or interest payments, or illiquidity in debt securities markets. To the extent that interest rates rise, certain underlying obligations may be paid off substantially slower than originally anticipated and the value of those securities may fall sharply. A rising interest rate environment may cause the value of the Fund's fixed income securities to decrease, an adverse impact on the liquidity of the Fund's fixed income securities, and increased volatility of the fixed income markets. During periods when interest rates are at low levels, the Fund's yield can be low, and the Fund may have a negative yield (i.e., it may lose money on an operating basis). To the extent that interest rates fall, certain underlying obligations may be paid off substantially faster than originally anticipated. If the principal on a debt obligation is prepaid before expected, the prepayments of principal may have to be reinvested in obligations paying interest at lower rates. During periods of falling interest rates, the income received by the Fund may decline. Changes in interest rates will likely have a greater effect on the values of debt securities of longer durations. Returns on investments in debt securities could trail the returns on other investment options, including investments in equity securities.
Asset Backed and Mortgage Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Asset-Backed and Mortgage-Backed Securities Risk: Asset-backed and mortgage-backed securities (residential and commercial) represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. These securities, in most cases, are not backed by the full faith and credit of the U.S. government, and there can be no assurance that the U.S. government would provide financial support to its agencies or instrumentalities where it is not obligated to do so. These securities may be subject to liquidity risk as well as the risk of illiquidity and default on the underlying asset or mortgage, particularly during periods of economic downturn. The liquidity of mortgage-backed and asset-backed securities may change over time. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain asset-backed and mortgage-backed securities. In particular, during periods of falling interest rates, mortgage-backed securities will be called or prepaid, which may result in the Fund having to reinvest proceeds in other investments at a lower interest rate. During periods of rising interest rates, the average life of a mortgage-backed security may extend, which may lock in a below-market interest rate, increase the security's duration, and reduce the value of the security. Enforcing rights against the underlying assets or collateral may be difficult, or the underlying assets or collateral may be insufficient if the issuer defaults. The values of certain types of mortgage-backed securities, such as inverse floaters and interest-only and principal-only securities, may be extremely sensitive to changes in interest rates and prepayment rates. Transactions in mortgage pass through securities may occur through the use of “to-be-announced” or “TBA Transactions”. Default by, or bankruptcy of, a counterparty to a TBA Transaction would expose the Fund to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools of mortgage pass-through securities specified in the TBA Transaction.
Below Investment Grade Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Below Investment-Grade Securities Risk: Lower-quality debt securities (“high yield” or “junk” bonds) are considered predominantly speculative, and can involve a substantially greater risk of default than higher quality debt securities. Issuers of lower-quality debt securities may have substantially greater risk of insolvency or bankruptcy than issuers of higher-quality debt securities. They can be illiquid, and their values can have significant volatility and may decline significantly over short periods of time. Lower-quality debt securities tend to be more sensitive to adverse news about the issuer, or the market or economy in general.
Fluctuation of Net Asset Value Share Premiums and Discounts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Fluctuation of Net Asset Value, Share Premiums and Discounts Risk: As with all exchange-traded funds, Fund Shares may be bought and sold in the secondary market at market prices. The trading prices of Fund Shares in the secondary market may differ from the Fund's daily net asset value (“NAV”) per share and there may be times when the market price of the shares is more than the NAV per share (premium) or less than the NAV per share (discount). This risk is heightened in times of market volatility or periods of steep market declines.
Bank Loan Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Bank Loan Risk: The Fund may invest in secured and unsecured participations in bank loans and assignments of such loans. In making investments in such loans, which are made by banks or other financial intermediaries to borrowers, the Fund will depend primarily upon the creditworthiness of the borrower for payment of principal and interest which will expose the Fund to the credit risk of both the financial institution and the underlying borrower. The market for bank loans may not be highly liquid and the Fund may have difficulty selling them. The Fund may also experience settlement delays with respect to bank loan trades, resulting in the proceeds from the sale of such loans not being readily available to make additional investments or to meet the Fund's redemption obligations. Participations by the Fund in a lender's portion of a bank loan typically will result in the Fund having a contractual relationship only with such lender, not with the borrower. The Fund may have the right to receive payments of principal, interest and any fees to which it is entitled only from the lender selling a loan participation and only upon receipt by such lender of such payments from the borrower. In connection with purchasing participations, the Fund generally will have no right to enforce compliance by the borrower with the terms of the loan agreement, nor any rights with respect to any funds acquired by other lenders through set-off against the borrower, and the Fund may not directly benefit from any collateral supporting the loan in which it has purchased the participation. As a result, the Fund may assume the credit risk of both the borrower and the lender selling the participation. Further, loans held by the Fund may not be considered securities and, therefore, purchasers, such as the Fund, may not be entitled to rely on the strong anti-fraud protections of the federal securities laws. Some of the loans in which the Fund may invest or obtain exposure to may be “covenant-lite” loans. Covenant-lite loans may contain fewer or no maintenance covenants compared to other loans and may not include terms which allow the lender to monitor the performance of the borrower and declare a default if certain criteria are breached. The Fund may experience delays in enforcing its rights on its holdings of covenant-lite loans.
Cash Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Cash Transaction Risk: The Fund may sell portfolio securities to meet some or all of a redemption request with cash. In such cases, the Fund may incur taxable gains or losses that it might not have incurred had it made redemptions entirely in-kind. As a result, the Fund may pay out higher annual capital gain distributions than if the in-kind redemption process was used.
Collateralized Debt Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Collateralized Debt Obligations Risk: The risks of an investment in a collateralized debt obligation depend largely on the type of the collateral securities and the class of the debt obligation in which the Fund invests. Collateralized debt obligations are generally subject to many of the same risks of investing as debt securities and asset-backed securities, including credit, interest rate, valuation, liquidity, prepayment and extension risks. These securities also are subject to risk of default on the underlying assets, particularly during periods of economic downturn.
Collateralized Loan Obligation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Collateralized Loan Obligation Risk: The risks of an investment in a collateralized loan obligation depend largely on the type of the collateral securities and the class of the collateralized loan obligation in which the Fund invests. Collateralized loan obligations are generally subject to credit, interest rate, valuation, liquidity, prepayment and extension risks. These securities also are subject to risk of default on the underlying asset, particularly during periods of economic downturn. Collateralized loan obligations carry additional risks including, but not limited to, (i) the possibility that distributions from collateral securities will not be adequate to make interest of other payments, (ii) the collateral may decline in value or default, (iii) the Fund may invest in obligations that are subordinate to other classes, and (iv) the complex structure of the security may not be fully understood at the time of investment and produce disputes with the issuer or unexpected investment results. Collateralized loan obligations are divided into two or more classes, called “tranches,” each with a different credit rating and risk/return profile. Tranches are categorized as senior, mezzanine and subordinated/equity, according to their degree of credit risk. If there are defaults or the collateralized loan obligation's collateral otherwise underperforms, scheduled payments to senior tranches take precedence over those of mezzanine tranches, and scheduled payments to mezzanine tranches take precedence over those of subordinated/equity tranches. Senior and mezzanine tranches are typically rated. The ratings reflect both the credit quality of underlying collateral as well as how much protection a given tranche is afforded by tranches that are subordinate to it.
Collateralized Bond Obligation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Collateralized Bond Obligation Risk: The pool of high yield securities underlying collateralized bond obligations is typically separated into groupings called tranches representing different degrees of credit quality. The higher quality tranches have greater degrees of protection and pay lower interest rates. The lower tranches, with greater risk, pay higher interest rates.
Collateralized Mortgage Obligation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Collateralized Mortgage Obligation Risk: The expected average life of collateralized mortgage obligations (“CMOs”) is determined using mathematical models that incorporate prepayment assumptions and other factors that involve estimates of future economic and market conditions. These estimates may vary from actual future results, particularly during periods of extreme market volatility. Further, under certain market conditions, the average weighted life of certain CMOs may not accurately reflect the price volatility of such securities. For example, in periods of supply and demand imbalances in the market for such securities and/or in periods of sharp interest rate movements, the prices of CMOs may fluctuate to a greater extent than would be expected from interest rate movements alone. CMOs issued by private entities are not obligations issued or guaranteed by the U.S. government, its agencies or instrumentalities and are not guaranteed by any government agency, although the securities underlying a CMO may be subject to a guarantee. Therefore, if the collateral securing the CMO, as well as any third party credit support or guarantees, is insufficient to make payments when due, the holder could sustain a loss.
Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Currency Risk: The value of the Fund's assets may be affected favorably or unfavorably by currency exchange rates, currency exchange control regulations, and delays, restrictions or prohibitions on the repatriation of foreign currencies. Foreign currency exchange rates may have significant volatility, and changes in the values of foreign currencies against the U.S. dollar may result in substantial declines in the values of the Fund's assets denominated in foreign currencies.
Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Emerging Markets Risk: Risks of investing in emerging markets include, among others, greater political and economic instability, greater volatility in currency exchange rates, less developed securities markets, increased potential for market manipulation, possible trade barriers, currency transfer restrictions, a more limited number of potential buyers and issuers, an emerging market country's dependence on revenue from particular commodities or international aid, less governmental supervision and regulation, unavailability of currency hedging techniques, differences in auditing and financial reporting standards, and less developed legal systems. There is also the potential for unfavorable action such as expropriation, nationalization, embargoes, and acts of war. The securities of emerging market companies may trade less frequently and in smaller volumes than more widely held securities. Market disruptions or substantial market corrections may limit very significantly the liquidity of securities of certain companies in a particular country or geographic region, or of all companies in the country or region. The Fund may be unable to liquidate its positions in such securities at any time, or at a favorable price, in order to meet the Fund's obligations. These risks are generally greater for investments in frontier market countries, which typically have smaller economies or less developed capital markets than traditional emerging market countries.
Exchange Traded Products Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Exchange Traded Products Risk: The Fund is subject to substantially the same risks as those associated with the direct ownership of the securities represented by the ETPs in which it invests. In addition, the shares of certain ETPs may trade at a premium or discount to their intrinsic value (i.e., the market value may differ from the net asset value of an exchange traded fund's (“ETF”) shares) for a number of reasons. For example, supply and demand for shares of an ETF or market disruptions may cause the market price of the ETF to deviate from the value of the ETF's investments, which may be exacerbated in less liquid markets. The value of an exchange traded note may also differ from the valuation of its reference market due to changes in the issuer's credit rating.
Income Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Income Risk: The Fund's income may decline due to falling interest rates or other factors. Issuers of securities held by the Fund may call or redeem the securities during periods of falling interest rates, and the Fund would likely be required to reinvest in securities paying lower interest rates. If an obligation held by the Fund is prepaid, the Fund may have to reinvest the prepayment in other obligations paying income at lower rates.
Inflation Indexed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Inflation-Indexed Securities Risk: The principal amount of an inflation-indexed security typically increases with inflation and decreases with deflation, as measured by a specified index. It is possible that, in a period of declining inflation rates, the Fund could receive at maturity less than the initial principal amount of an inflation-indexed security. Changes in the values of inflation-indexed securities may be difficult to predict, and it is possible that an investment in such securities will have an effect different from that anticipated by the Sub-Adviser.
Interest Rate Only and Principal Only Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Interest Rate Only and Principal Only Securities Risk: Interest rate only and principal only securities are acutely sensitive to interest rate changes and to the rate of principal prepayments. These securities are volatile in price and may have lower liquidity.
Investment in ETNs [Member]  
Prospectus [Line Items]  
Risk [Text Block] Investment in ETNs: The value of an exchanged traded note (“ETN”) may be influenced by time to maturity, supply and demand, volatility and lack of liquidity, changes in interest rates, and economic, legal, political or geographic events that affect the referenced market. Because ETNs are debt securities, they are subject to credit risk. There are typically no periodic interest payments for ETNs, and the amount of principal payable at maturity may decline, depending in part on the performance of an underlying index or asset. A Fund could lose all or some of the amount invested in an ETN.
Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Liquidity Risk: Lack of a ready market, stressed market conditions, or restrictions on resale may limit the ability of the Fund to sell a security at an advantageous time or price or at all. Illiquid investments may trade at a discount from comparable, more liquid investments and may be subject to wide fluctuations in market value. If the liquidity of the Fund's holdings deteriorates, it may lead to differences between the market price of Fund Shares and the NAV of Fund Shares, and could result in the Fund Shares being less liquid. Illiquidity of the Fund's holdings may also limit the ability of the Fund to obtain cash to meet redemptions on a timely basis.  In addition, the Fund, due to limitations on investments in any illiquid investments and/or the difficulty in purchasing and selling such investments, may be unable to achieve its desired level of exposure to a certain market or sector.
Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Management Risk: The Fund is actively managed. The Sub-Adviser's judgments about the attractiveness, relative value, or potential appreciation of a particular sector, security, commodity or investment strategy may prove to be incorrect, and may cause the Fund to incur losses. There can be no assurance that the Sub-Adviser's investment techniques and decisions will produce the desired results.
Municipal Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Municipal Obligations Risk: Issuers, including governmental issuers, may be unable to pay their obligations as they come due. The values of municipal obligations may be adversely affected by local political and economic conditions and developments. In addition, the values of municipal obligations that depend on a specific revenue source to fund their payment obligations may fluctuate as a result of actual or anticipated changes in the cash flows generated by the revenue source or changes in the priority of the municipal obligation to receive the cash flows generated by the revenue source. Municipal obligations may be more susceptible to downgrades or defaults during recessions or similar periods of economic stress. In addition, changes in U.S. federal tax laws or the activity of an issuer may adversely affect the tax-exempt status of municipal obligations. Loss of tax-exempt status may result in a significant decline in the values of such municipal obligations.
Non U S Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Non-U.S. Securities Risk: Non-U.S. securities are subject to political, regulatory, and economic risks not present in domestic investments. There may be less information publicly available about a non-U.S. entity than about a U.S. entity, and many non-U.S. entities are not subject to accounting, auditing, legal and financial report standards comparable to those in the United States. Further, such entities and/or their securities may be subject to risks associated with currency controls; expropriation; changes in tax policy; greater market volatility; differing securities market structures; higher transaction costs; and various administrative difficulties, such as delays in clearing and settling portfolio transactions or in receiving payment of dividends. To the extent underlying securities held by the Fund trade on foreign exchanges that are closed when the exchange on which the Fund's shares trade is open, there may be deviations between the current price of an underlying security and the last quoted price for the underlying security on the closed foreign market. These deviations could result in the Fund experiencing premiums or discounts greater than those of ETFs that invest in domestic securities. Securities traded on foreign markets may be less liquid (harder to sell) than securities traded domestically. Foreign governments may impose restrictions on the repatriation of capital to the U.S. In addition, to the extent the Fund buys securities denominated in a foreign currency, there are special risks such as changes in currency exchange rates and the risk that a foreign government could regulate foreign exchange transactions.  In addition, to the extent investments are made in a limited number of countries, events in those countries will have a more significant impact on the Fund. Certain countries may institute negative interest rates on certain fixed-income securities, and similar interest rate conditions may be experienced in other regions. Investments in fixed-income securities with very low or negative interest rates may magnify the Fund's susceptibility to interest rate risk and diminish yield and performance, and such investments may be subject to heightened volatility and reduced liquidity.
Political Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Political Risk: A significant restructuring of federal income tax rates or even serious discussion on the topic in Congress could cause municipal bond prices to fall. The demand for municipal securities is strongly influenced by the value of tax-exempt income to investors. Lower income tax rates could reduce the advantage of owning municipals.
Preferred Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Preferred Securities Risk: Generally, preferred security holders have no or limited voting rights with respect to the issuing company. In addition, preferred securities are generally senior to common stock, but may be subordinated to bonds and other debt instruments in a company's capital structure and therefore may be subject to greater credit risk than those debt instruments. In the event an issuer of preferred securities experiences economic difficulties, the issuer's preferred securities may lose substantial value due to the increased likelihood of deferred interest or dividend payments and the fact that the preferred security may be subordinated to other securities of the same issuer. Further, because many preferred securities pay interest or dividends at a fixed rate, their market price can be sensitive to changes in interest rates in a manner similar to bonds — that is, as interest rates rise, the value of the preferred securities held by the Fund are likely to decline. In addition, to the extent preferred securities allow holders to convert the preferred securities into common stock of the issuer, their market price can be sensitive to changes in the value of the issuer's common stock and, therefore, declining common stock values may also cause the value of the Fund's investments to decline. Preferred securities often have call features which allow the issuer to redeem the security at its discretion. The redemption of a preferred security having a higher than average yield may cause a decrease in the Fund's yield.
Privately Issued Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Privately Issued Securities Risk: The Fund will invest in privately-issued securities, including those which are issued pursuant to Rule 144A or Regulation S under the Securities Act of 1933, or Section 4(a)(2) of the Securities Act 1933. Privately-issued securities are securities that have not been registered under the Securities Act and as a result are subject to legal restrictions on resale. Privately-issued securities are not traded on established markets and may be illiquid, difficult to value and subject to wide fluctuations in value. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Fund from disposing of them promptly at reasonable prices.
REMIC Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] REMIC Risk: The issuer of a series of mortgage pass-through securities may elect to be treated as a Real Estate Mortgage Investment Conduit (“REMIC”). REMICs include governmental and/or private entities that issue a fixed pool of mortgages secured by an interest in real property. REMICs are similar to collateralized mortgage obligations (“CMOs”) in that they issue multiple classes of securities but, unlike CMOs, which are required to be structured as debt securities, REMICs may be structured as indirect ownership interests in the underlying assets of the REMICs themselves. The risks associated with an investment in a particular CMO or REMIC class vary substantially depending on the combination of rights associated with that class. An investment in the most subordinated classes of a CMO or REMIC bears a disproportionate share of the risks associated with mortgage-backed security generally, be it credit risk, prepayment or extension risk (the risk of a security's expected maturity being reduced or lengthened in duration due to a change of the timing of payment), interest rate risk, income risk, market risk, liquidity risk or any other risk associated with a debt or equity instrument with similar features to the relevant class. As a result, an investment in the most subordinated classes of a CMO or REMIC is often riskier than an investment in other types of mortgage-backed securities.
Restricted Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Restricted Securities Risk: The Fund may hold securities that have not been registered for sale to the public under the U.S. federal securities laws. There can be no assurance that a trading market will exist at any time for any particular restricted security. Limitations on the resale of these securities may have an adverse effect on their marketability, and may prevent the Fund from disposing of them promptly at reasonable prices. The Fund may have to bear the expense of registering the securities for resale and the risk of substantial delays in effecting the registration. Also, restricted securities may be difficult to value because market quotations may not be readily available, and the securities may have significant volatility.
Sovereign Debt Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Sovereign Debt Obligations Risk: Investments in debt securities issued by governments or by government agencies and instrumentalities involve the risk that the governmental entities responsible for repayment may be unable or unwilling to pay interest and repay principal when due. Any restructuring of a sovereign debt obligation held by the Fund will likely have a significant adverse effect on the value of the obligation. In the event of default of sovereign debt, the Fund may be unable to pursue legal action against the sovereign issuer or to realize on collateral securing the debt.
Unconstrained Sector Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Unconstrained Sector Risk: The Fund may invest a substantial portion of its assets within one or more economic sectors or industries, which may change from time to time. Greater investment focus on one or more sectors or industries increases the potential for volatility and the risk that events negatively affecting such sectors or industries could reduce returns, potentially causing the value of the Fund's Shares to decrease, perhaps significantly.
US Government Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] U.S. Government Securities Risk: Certain U.S. government securities are supported by the full faith and credit of the United States; others are supported by the right of the issuer to borrow from the U.S. Treasury; others are supported by the discretionary authority of the U.S. government to purchase the agency's obligations; and still others are supported only by the credit of the issuing agency, instrumentality, or enterprise. Although U.S. government-sponsored enterprises such as the Federal Home Loan Mortgage Corporation (“Freddie Mac”) and the Federal National Mortgage Association (“Fannie Mae”) may be chartered or sponsored by Congress, they are not funded by Congressional appropriations, and their securities are not issued by the U.S. Treasury, are not supported by the full faith and credit of the U.S. government, and involve increased credit risks.
US Treasury Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] U.S. Treasury Obligations Risk: U.S. Treasury obligations may differ from other fixed income securities in their interest rates, maturities, times of issuance and other characteristics. Similar to other issuers, changes to the financial condition or credit rating of the U.S. government may cause the value of the Fund's U.S. Treasury obligations to decline.
Valuation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Valuation Risk: Certain portfolio holdings may be valued on the basis of factors other than market quotations. This may occur more often in times of market turmoil or reduced liquidity. There are multiple methods that can be used to value a portfolio holding when market quotations are not readily available. The value established for any portfolio holding at a point in time might differ from what would be produced using a different methodology or if it had been priced using market quotations. Portfolio holdings that are valued using techniques other than market quotations, including “fair valued” securities, may be subject to greater fluctuation in their valuations from one day to the next than if market quotations were used. In addition, there is no assurance that the Fund could sell or close out a portfolio position for the value established for it at any time, and it is possible that the Fund would incur a loss because a portfolio position is sold or closed out at a discount to the valuation established by the Fund at that time.
Variable and Floating Rate Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Variable and Floating Rate Securities Risk: During periods of increasing interest rates, changes in the coupon rates of variable or floating rate securities may lag behind the changes in market rates or may have limits on the maximum increases in coupon rates. Alternatively, during periods of declining interest rates, the coupon rates on such securities will typically readjust downward resulting in a lower yield. Floating rate notes are generally subject to legal or contractual restrictions on resale, may trade infrequently, and their value may be impaired when the Fund needs to liquidate such securities.
Zero Coupon Bond Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block] Zero-Coupon Bond Risk: Zero-coupon bonds usually trade at a deep discount from their face or par values and are subject to greater market value fluctuations from changing interest rates than debt obligations of comparable maturities that make current distributions of interest.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] As with all investments, there are certain risks of investing in the Fund. Fund Shares will change in value, and you could lose money by investing in the Fund.
Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.