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Class K [Member] Investment Risks - Class K - BlackRock LifePath ESG Index 2035 Fund
Oct. 31, 2025
Equity Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Equity Securities Risk — Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.
Investments in Underlying Funds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Investments in Underlying Funds Risk — Because the Fund invests substantially all of its assets in Underlying Funds, its investment performance is related to the performance of the Underlying Funds. The Fund’s net asset value will change with changes in the value of the Underlying Funds and other securities in which it invests. An investment in the Fund will entail more direct and indirect costs and expenses than a direct investment in the Underlying Funds.
Allocation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Allocation Risk — The Fund’s ability to achieve its investment objective depends upon the Fund’s asset class allocation and the mix of Underlying Funds. There is a risk that the asset class allocation or the combination of Underlying Funds may be incorrect in view of actual market conditions. In addition, the asset allocation or the combination of Underlying Funds determined by BFA could result in underperformance as compared to funds with similar investment objectives and strategies.
Retirement Income Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Retirement Income Risk — The Fund does not provide a guarantee that sufficient capital appreciation will be achieved to provide adequate income at and through retirement. The Fund also does not ensure that you will have assets in your account sufficient to cover your retirement expenses or that you will have enough saved to be able to retire in the target year identified in the Fund’s name; this will depend on the amount of money you have invested in the Fund, the length of time you have held your investment, the returns of the markets over time, the amount you spend in retirement, and your other assets and income sources.
Risk of ESG Investing [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Risk of ESG Investing — The Fund intends to invest a portion of its assets in Underlying Funds that seek to maximize exposure to companies with higher ESG ratings. This may affect the Fund’s exposure to certain companies or industries and the Fund will forgo certain investment opportunities. The Fund’s results may be lower than other funds that do not seek to invest in companies based on ESG ratings and/or screen out certain companies or industries. The index provider for an Underlying Fund’s underlying index seeks to identify companies that it believes may have higher ESG ratings, but investors may differ in their views of ESG characteristics. Additionally, certain Underlying Funds may not screen out investments based on certain ESG standards. As a result, the Fund may invest in companies that do not reflect the beliefs and values of any particular investor.
Affiliated Fund Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Affiliated Fund Risk — In managing the Fund, BFA will have authority to select and substitute underlying funds and ETFs. BFA may be subject to conflicts of interest in selecting underlying funds and ETFs because the fees paid to BFA by some underlying funds and ETFs are higher than the fees paid by other underlying funds and ETFs. However, BFA is a fiduciary to the Fund and is legally obligated to act in the Fund’s best interests when selecting underlying funds and ETFs. If an underlying fund or ETF holds interests in an affiliated fund, the Fund may be prohibited from purchasing shares of that underlying fund or ETF.
Market Risk and Selection Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. The value of a security or other asset may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security or other asset, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues like pandemics or epidemics, recessions, or other events could have a significant impact on the Fund and its investments. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
Operational and Technology Risks [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Operational and Technology Risks — The Fund is directly and indirectly susceptible to operational and technology risks, including those related to human errors, processing errors, communication errors, systems failures, cybersecurity incidents, and the use of artificial intelligence and machine learning (“AI”), which may result in losses for the Fund and its shareholders or may impair the Fund’s operations. While the Fund’s service providers are required to have appropriate operational, information security and cybersecurity risk management policies and procedures, their methods of risk management may differ from those of the Fund. Operational and technology risks for the issuers in which the Fund invests could also result in material adverse consequences for such issuers and may cause the Fund’s investments in such issuers to lose value.
Risk of Investing in the United States [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Risk of Investing in the United States — Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.
Asset Class Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Asset Class Risk — The securities and other assets in an underlying index or in the Fund’s portfolio may underperform in comparison to financial markets generally, a particular financial market, another index, or other asset classes.
Authorized Participant Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Authorized Participant Concentration Risk — Only an authorized participant may engage in creation or redemption transactions directly with an ETF. An ETF has a limited number of institutions that may act as authorized participants, including on an agency basis. To the extent that authorized participants exit the business or do not place creation or redemption orders with respect to an ETF and no other authorized participant places orders, ETF shares are more likely to trade at a premium or discount to net asset value and possibly face trading halts or delisting.
Commodities Related Investments Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Commodities Related Investments Risk — Exposure to the commodities markets may subject the Fund to greater volatility than investments in traditional securities. The value of commodity-linked derivative investments may be affected by changes in overall market movements, commodity index volatility, changes in inflation, interest rates, or factors affecting a particular industry or commodity, such as drought, floods, weather, embargoes, tariffs and international economic, political and regulatory developments.
Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Concentration Risk — To the extent that an underlying index of an Underlying Fund is concentrated in the securities of companies, a particular market, industry, group of industries, sector or asset class, country, region or group of countries, that Underlying Fund may be adversely affected by the performance of those securities, may be subject to increased price volatility and may be more susceptible to adverse economic, market, political or regulatory occurrences affecting that market, industry, group of industries, sector or asset class, country, region or group of countries.
Depositary Receipts Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Depositary Receipts Risk — Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. In addition to investment risks associated with the underlying issuer, depositary receipts expose the Fund to additional risks associated with the non‑uniform terms that apply to depositary receipt programs, credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency risk and the risk of an illiquid market for depositary receipts. The issuers of unsponsored depositary receipts are not obligated to disclose information that is, in the United States, considered material. Therefore, there may be less information available regarding these issuers and there may not be a correlation between such information and the market value of the depositary receipts. While depositary receipts provide an alternative to directly purchasing underlying foreign securities in their respective markets and currencies, they continue to be subject to many of the risks associated with investing directly in foreign securities, including political, economic, and currency risk.
Derivatives Risks [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Derivatives Risk — The Fund’s use of derivatives may increase its costs, reduce the Fund’s returns and/or increase volatility. Derivatives involve significant risks, including:
Leverage Risk — The Fund’s use of derivatives can magnify the Fund’s gains and losses. Relatively small market movements may result in large changes in the value of a derivatives position and can result in losses that greatly exceed the amount originally invested.
Market Risk — Some derivatives are more sensitive to interest rate changes and market price fluctuations than other securities. The Fund could also suffer losses related to its derivatives positions as a result of unanticipated market movements, which losses are potentially unlimited. Finally, BFA may not be able to predict correctly the direction of securities prices, interest rates and other economic factors, which could cause the Fund’s derivatives positions to lose value.
Counterparty Risk — Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will be unable or unwilling to fulfill its contractual obligation, and the related risks of having concentrated exposure to such a counterparty.
Illiquidity Risk — The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately.
Operational Risk — The use of derivatives includes the risk of potential operational issues, including documentation issues, settlement issues, systems failures, inadequate controls and human error.
Legal Risk — The risk of insufficient documentation, insufficient capacity or authority of counterparty, or legality or enforceability of a contract.
Volatility and Correlation Risk — Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate with the overall securities markets.
Valuation Risk — Valuation for derivatives may not be readily available in the market. Valuation may be more difficult in times of market turmoil since many investors and market makers may be reluctant to purchase complex instruments or quote prices for them.
Hedging Risk — Hedges are sometimes subject to imperfect matching between the derivative and the underlying security, and there can be no assurance that the Fund’s hedging transactions will be effective. The use of hedging may result in certain adverse tax consequences.
Tax Risk — Certain aspects of the tax treatment of derivative instruments, including swap agreements and commodity-linked derivative instruments, are currently unclear and may be affected by changes in legislation, regulations or other legally binding authority. Such treatment may be less favorable than that given to a direct investment in an underlying asset and may adversely affect the timing, character and amount of income the Fund realizes from its investments.
Emerging Markets Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging financial markets have far lower trading volumes and less liquidity than developed markets.
Foreign Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:
   
The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.
   
Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.
   
The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.
   
The governments of certain countries, or the U.S. Government with respect to certain countries, may prohibit or impose substantial restrictions through capital controls and/or sanctions on foreign investments in the capital markets or certain industries in those countries, which may prohibit or restrict the ability to own or transfer currency, securities, derivatives or other assets.
   
Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.
   
Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.
   
The Fund’s claims to recover foreign withholding taxes may not be successful, and if the likelihood of recovery of foreign withholding taxes materially decreases, due to, for example, a change in tax regulation or approach in the foreign country, accruals in the Fund’s net asset value for such refunds may be written down partially or in full, which will adversely affect the Fund’s net asset value.
Geographic Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Geographic Risk — Some of the companies in which the Fund invests are located in parts of the world that have historically been prone to natural disasters, such as earthquakes, tornadoes, volcanic eruptions, droughts, floods, hurricanes or tsunamis, and are economically sensitive to environmental events. Any such event may adversely impact the economies of these geographic areas or business operations of companies in these geographic areas, causing an adverse impact on the value of the Fund.
Income Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Income Risk — The Fund’s income may decline due to a decline in inflation, deflation or changes in inflation expectations.
Index Related Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Index-Related Risk — For the Underlying Funds, an index provider may rely on various sources of information to assess the criteria of components of an underlying index, including information that may be based on assumptions and estimates. Neither the Fund nor BFA can offer assurances that an index provider’s methodology or sources of information will provide an accurate assessment of included components. Errors in index data, index computations or the construction of the underlying indexes in accordance with its methodology may occur, and an index provider may not identify or correct them promptly or at all, which may have an adverse impact on the applicable Underlying Fund and its shareholders. Unusual market conditions or other unforeseen circumstances (such as natural disasters, political unrest or war) may impact an index provider or a third-party data provider and could cause an index provider to postpone a scheduled rebalance. This could cause the underlying index to vary from its normal or expected composition.
Inflation Indexed Bonds Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Inflation-Indexed Bonds Risk — The principal value of an investment in the Fund is not protected or otherwise guaranteed by virtue of any investments by the Fund in inflation-indexed bonds. The value of inflation-indexed
 
securities generally fluctuates with changes in real interest rates, decreasing when real interest rates rise and increasing when real interest rates fall. Real interest rates represent nominal (or stated) interest rates minus the inflation rates. If the Fund purchases TIPS in the secondary market and the bonds’ principal values previously were adjusted upward, but then there is a period of declining inflation rates, the Fund may receive at maturity less than it invested.
In addition, interest payments on inflation-indexed securities generally vary up or down along with the rate of inflation, and inflation-indexed bonds typically have lower nominal yields than conventional fixed-rate bonds. If the index measuring inflation falls, the principal value of inflation-indexed bonds will be adjusted downward, and consequently the interest payable on these securities (calculated with respect to a smaller principal amount) will be reduced.
Any increase in the principal amount of an inflation-indexed bond will be considered taxable ordinary income, even though investors do not receive their principal until maturity.
Periodic adjustments for inflation to the principal amount of an inflation-indexed bond may give rise to original issue discount, which will be includable in the Fund’s gross income. Due to original issue discount, the Fund may be required to make annual distributions to shareholders that exceed the cash received, which may cause the Fund to liquidate certain investments when it is not advantageous to do so. Also, if the principal value of an inflation-indexed bond is adjusted downward due to deflation, amounts previously distributed in the taxable year may be characterized in some circumstances as a return of capital.
Issuer Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Issuer Risk — Fund performance depends on the performance of individual securities to which the Fund has exposure. Changes in the financial condition or credit rating of an issuer of those securities may cause the value of the securities to decline.
Large Capitalization Companies Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Large-Capitalization Companies Risk — Large-capitalization companies may be less able than smaller-capitalization companies to adapt to changing market conditions and competitive challenges. Large-capitalization companies may be more mature and subject to more limited growth potential compared with smaller-capitalization companies. The performance of large-capitalization companies could trail the overall performance of the broader securities markets.
Large Shareholder and Large Scale Redemption Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Large Shareholder and Large-Scale Redemption Risk — Certain shareholders, including a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, or another entity, may from time to time own or manage a substantial amount of Fund shares, or may invest in the Fund and hold its investment for a limited period of time. There can be no assurance that any large shareholder or large group of shareholders would not redeem their investment. Redemptions by large shareholders or a large group of shareholders could have a significant negative impact on the Fund. Redemptions of a large number of Fund shares could require the Fund to dispose of assets to meet the redemption requests, which can accelerate the realization of taxable income and cause the Fund to make taxable distributions to its shareholders earlier than the Fund otherwise would have. In addition, under certain circumstances, non-redeeming shareholders may be treated as receiving a disproportionately large taxable distribution during or with respect to such year. In some circumstances, the Fund may hold a relatively large proportion of its assets in cash in anticipation of large redemptions, diluting its investment returns. These large redemptions may also force the Fund to sell portfolio securities when it might not otherwise do so, which may negatively impact the Fund’s NAV and increase the Fund’s brokerage costs and/or accelerate the realization of taxable income and/or capital gains to shareholders. In addition, large redemptions can result in the Fund’s current expenses being allocated over a smaller asset base, which generally results in an increase in the Fund’s expense ratio. Because large redemptions can adversely affect a portfolio manager’s ability to implement a fund’s investment strategy, the Fund also reserves the right to redeem in-kind, subject to certain conditions.
Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Management Risk — As an Underlying Fund may not fully replicate its underlying index, it is subject to the risk that the Underlying Fund’s investment manager’s investment management strategy may not produce the intended results.
National Closed Market Trading Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
National Closed Market Trading Risk — To the extent that the underlying securities or other instruments held by an ETF trade on foreign exchanges or in foreign markets that may be closed when the securities exchange on which the ETF’s shares trade is open, there are likely to be deviations between the current price of such an underlying security and the last quoted price for the underlying security (i.e., the ETF’s quote from the closed foreign market). The impact of a closed foreign market on the Fund is likely to be greater where a large portion of the Fund’s underlying securities or other instruments trade on that closed foreign market or when the foreign market is closed for unscheduled reasons. These deviations could result in premiums or discounts to the ETF’s net asset value that may be greater than those experienced by other ETFs.
Passive Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Passive Investment Risk — Because BFA does not select individual companies in the underlying indexes for certain Underlying Funds, those Underlying Funds may hold securities of companies that present risks that an investment adviser researching individual securities might seek to avoid.
Real Estate Related Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Real Estate-Related Securities Risk — The main risk of real estate-related securities is that the value of the underlying real estate may go down. Many factors may affect real estate values. These factors include both the general and local economies, vacancy rates, changes in rent schedules, tenant bankruptcies, the ability to re‑lease space under expiring leases on attractive terms, the amount of new construction in a particular area, the laws and
 
regulations (including zoning, environmental and tax laws) affecting real estate and the costs of owning, maintaining and improving real estate. The availability of mortgage financing and changes in interest rates may also affect real estate values. If the Fund’s real estate-related investments are concentrated in one geographic area or in one property type, the Fund will be particularly subject to the risks associated with that area or property type. Many issuers of real estate-related securities are highly leveraged, which increases the risk to holders of such securities. The value of the securities the Fund buys will not necessarily track the value of the underlying investments of the issuers of such securities. In addition, certain issuers of real estate-related securities may have developed or commenced development on properties and may develop additional properties in the future. Real estate development involves significant risks in addition to those involved in the ownership and operation of established properties. Real estate securities may have limited diversification and are, therefore, subject to risks inherent in operating and financing a limited number of projects. Real estate securities are also subject to heavy cash flow dependency and defaults by borrowers or tenants.
REIT Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
REIT Investment Risk — Investments in REITs involve unique risks. REITs may have limited financial resources, may trade less frequently and in limited volume, may engage in dilutive offerings of securities and may be more volatile than other securities. REIT issuers may also fail to maintain their exemptions from investment company registration or fail to qualify for the “dividends paid deduction” under the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”), which allows REITs to reduce their corporate taxable income for dividends paid to their shareholders.
Representative Sampling Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Representative Sampling Risk — Representative sampling is a method of indexing that involves investing in a representative sample of securities that collectively have a similar investment profile to the index and resemble the index in terms of risk factors and other key characteristics. A passively managed ETF may or may not hold every security in the index. When an ETF deviates from a full replication indexing strategy to utilize a representative sampling strategy, the ETF is subject to an increased risk of tracking error, in that the securities selected in the aggregate for the ETF may not have an investment profile similar to those of its index.
Shares of an ETF May Trade at Prices Other Than Net Asset Value [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Shares of an ETF May Trade at Prices Other Than Net Asset Value — Shares of an ETF trade on exchanges at prices at, above or below their most recent net asset value. The per share net asset value of an ETF is calculated at the end of each business day and fluctuates with changes in the market value of the ETF’s holdings since the most recent calculation. The trading prices of an ETF’s shares fluctuate continuously throughout trading hours based on market supply and demand rather than net asset value. The trading prices of an ETF’s shares may deviate significantly from net asset value during periods of market volatility. Any of these factors may lead to an ETF’s shares trading at a premium or discount to net asset value. However, because shares can be created and redeemed in creation units, which are aggregated blocks of shares that authorized participants who have entered into agreements with the ETF’s distributor can purchase or redeem directly from the ETF, at net asset value (unlike shares of many closed‑end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their net asset values), large discounts or premiums to the net asset value of an ETF are not likely to be sustained over the long-term. While the creation/redemption feature is designed to make it likely that an ETF’s shares normally trade on exchanges at prices close to the ETF’s next calculated net asset value, exchange prices are not expected to correlate exactly with an ETF’s net asset value due to timing reasons as well as market supply and demand factors. In addition, disruptions to creations and redemptions or the existence of extreme market volatility may result in trading prices that differ significantly from net asset value. If a shareholder purchases at a time when the market price is at a premium to the net asset value or sells at a time when the market price is at a discount to the net asset value, the shareholder may sustain losses. The use of cash creations and redemptions may also cause the ETFs’ shares to trade in the market at greater bid-ask spreads or greater premiums or discounts to the ETFs’ net asset value.
Small and Mid Capitalization Company Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Small and Mid‑Capitalization Company Risk — Companies with small or mid‑size market capitalizations will normally have more limited product lines, markets and financial resources and will be dependent upon a more limited management group than larger capitalized companies. In addition, it is more difficult to get information on smaller companies, which tend to be less well known, have shorter operating histories, do not have significant ownership by large investors and are followed by relatively few securities analysts.
Tracking Error Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Tracking Error Risk — An Underlying Fund is subject to the risk of “tracking error,” which is the divergence of an Underlying Fund’s performance from that of its underlying index. Tracking error may occur due to a number of factors, including differences between the securities and other assets held in an Underlying Fund’s portfolio and those included in its underlying index; differences in the timing and methodologies used to value securities and other assets; transaction costs and other expenses incurred by an Underlying Fund that its underlying index does not incur; an Underlying Fund’s holding of uninvested cash; differences in the timing of the accrual or the valuation of dividends or interest received by an Underlying Fund or distributions paid to an Underlying Fund’s shareholders; tax gains or losses; differences between the amount and/or timing of withholding taxes on dividends reflected in an underlying index from the Underlying Fund’s obligation, if any, for foreign withholding taxes; the requirements for an Underlying Fund to maintain pass-through tax treatment; portfolio transactions carried out to minimize the distribution of capital gains to shareholders; changes to an underlying index, such as during a rebalancing or reconstitution; and impacts to an Underlying Fund of complying with certain regulatory requirements or limits. A fund that tracks an index composed of a large number of securities or other assets may experience greater tracking error than a fund that tracks a more narrow index. Tracking error risk may be heightened during times of increased market volatility or other unusual market conditions.
Treasury Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Treasury Obligations Risk — Direct obligations of the U.S. Treasury have historically involved little risk of loss of principal if held to maturity. However, due to fluctuations in interest rates, the market value of such securities may vary during the period shareholders own shares of the Fund. In addition, notwithstanding that U.S. Treasury obligations are backed by the full faith and credit of the United States, circumstances could arise that could prevent the timely payment of interest or principal, such as reaching the legislative “debt ceiling.” Such non-payment could result in losses to the Fund and substantial negative consequences for the U.S. economy and the global financial system.
U S Agency Mortgage Backed Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
U.S. Agency Mortgage-Backed Securities Risk MBS represent interests in “pools” of mortgages and are subject to interest rate, prepayment, and extension risk. MBS may be issued or guaranteed by the U.S. government or one of its agencies or sponsored entities. Some MBS may not be backed by the full faith and credit of the U.S. government and thus represent greater credit risk. MBS react differently than other bonds to changes in interest rates due to prepayment and extension risks. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain MBS. MBS prices may reflect adverse economic and market conditions. MBS are subject to the risk of default on the underlying mortgage loans, particularly during periods of economic downturn. The default or bankruptcy of a counterparty to a TBA transaction would expose the Fund to possible losses.
U S Government Obligations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
U.S. Government Obligations Risk — Certain securities in which the Fund may invest, including securities issued by certain U.S. Government agencies and U.S. Government sponsored enterprises, are not guaranteed by the U.S. Government or supported by the full faith and credit of the United States. In addition, circumstances could arise that could prevent the timely payment of interest or principal on U.S. Government obligations, such as reaching the legislative “debt ceiling.” Such non-payment could result in losses to the Fund and substantial negative consequences for the U.S. economy and the global financial system.
Valuation Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Valuation Risk — The price the Fund could receive upon the sale of any particular portfolio investment may differ from the Fund’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair valuation methodology or a price provided by an independent pricing service. As a result, the price received upon the sale of an investment may be less than the value ascribed by the Fund, and the Fund could realize a greater than expected loss or lesser than expected gain upon the sale of the investment. Pricing services that value fixed-income securities generally utilize a range of market-based and security-specific inputs and assumptions, as well as considerations about general market conditions, to establish a price. Pricing services generally value fixed-income securities assuming orderly transactions of an institutional round lot size, but may be held or transactions may be conducted in such securities in smaller, odd lot sizes. Odd lots of securities in certain asset classes may trade at lower prices than institutional round lots, and the value ultimately realized when the securities are sold could differ from the prices used by the Fund. The Fund’s ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third-party service providers.
Debt Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
 
Debt Securities Risk — Debt securities, such as bonds, involve risks, such as credit risk, interest rate risk, extension risk, and prepayment risk, each of which are described in further detail below:
Credit Risk — Credit risk refers to the possibility that the issuer of a debt security (i.e., the borrower) will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. The degree of credit risk depends on both the financial condition of the issuer and the terms of the obligation.
Interest Rate Risk — The market value of bonds and other fixed-income securities changes in response to interest rate changes and other factors. Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall and decrease as interest rates rise.
The Fund may be subject to a greater risk of rising interest rates during a period of historically low interest rates. For example, if interest rates increase by 1%, assuming a current portfolio duration of ten years, and all other factors being equal, the value of the Fund’s investments would be expected to decrease by 10%. (Duration is a measure of the price sensitivity of a debt security or portfolio of debt securities to relative changes in interest rates.) The magnitude of these fluctuations in the market price of bonds and other fixed-income securities is generally greater for those securities with longer maturities. Fluctuations in the market price of the Fund’s investments will not affect interest income derived from instruments already owned by the Fund, but will be reflected in the Fund’s net asset value. The Fund may lose money if short-term or long-term interest rates rise sharply in a manner not anticipated by Fund management.
To the extent the Fund invests in debt securities that may be prepaid at the option of the obligor (such as mortgage-backed securities), the sensitivity of such securities to changes in interest rates may increase (to the detriment of the Fund) when interest rates rise. Moreover, because rates on certain floating rate debt securities typically reset only periodically, changes in prevailing interest rates (and particularly sudden and significant changes) can be expected to cause some fluctuations in the net asset value of the Fund to the extent that it invests in floating rate debt securities.
These basic principles of bond prices also apply to U.S. Government securities. A security backed by the “full faith and credit” of the U.S. Government is guaranteed only as to its stated interest rate and face value at maturity, not its current market price. Just like other fixed-income securities, government-guaranteed securities will fluctuate in value when interest rates change.
A general rise in interest rates has the potential to cause investors to move out of fixed-income securities on a large scale, which may increase redemptions from funds that hold large amounts of fixed-income securities. Heavy redemptions could cause the Fund to sell assets at inopportune times or at a loss or depressed value and could hurt the Fund’s performance.
Extension Risk— When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these obligations to fall.
Prepayment Risk — When interest rates fall, certain obligations will be paid off by the obligor more quickly than originally anticipated, and the Fund may have to invest the proceeds in securities with lower yields.
Risk of Investing in the United States — Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.
Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the Fund is not a bank deposit and it is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.