497

	SIDLEY AUSTIN LLP 787 SEVENTH AVENUE NEW YORK, NY 10019 (212) 839 5300 (212) 839 5599 FAX	BEIJING BRUSSELS CHICAGO DALLAS FRANKFURT GENEVA HONG KONG HOUSTON LONDON	LOS ANGELES NEW YORK PALO ALTO SAN FRANCISCO SHANGHAI SINGAPORE SYDNEY TOKYO WASHINGTON, D.C.
		FOUNDED 1866

January 24, 2013

VIA EDGAR

Securities and Exchange Commission

100 F Street, NE

Washington, DC 20549

Re: BlackRock CoreAlpha Bond Fund, a series of BlackRock Funds III

(File Nos. 33-54126, 811-07332)

Ladies and Gentlemen:

On behalf of BlackRock Funds III, attached for filing are exhibits containing interactive data format risk/return summary information that mirrors the risk/return summary information in the Prospectus of BlackRock CoreAlpha Bond Fund (the “Fund”), dated April 30, 2012, as amended December 28, 2012, as filed pursuant to Rule 497(e) under the Securities Act of 1933, on December 28, 2012 (the “497 Filing”). The purpose of this filing is to submit the 497 Filing in XBRL for the Fund.

Any questions or comments on the 497 Filing should be directed to the undersigned at (212) 839-5583.

Very truly yours,

/s/ Ellen W. Harris

Ellen W. Harris

Enclosures

cc: Benjamin Archibald, Esq.

BlackRock Advisors, LLC

Sidley Austin (NY) LLP is a Delaware limited liability partnership doing business as Sidley Austin LLP and practicing in affiliation with other Sidley Austin partnerships.

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Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BlackRock Funds III
Prospectus Date	rr_ProspectusDate	Apr. 30, 2012
BlackRock CoreAlpha Bond Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Overview Key Facts about BlackRock CoreAlpha Bond Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	BlackRock CoreAlpha Bond Fund (the “Fund”), a series of BlackRock Funds III (the “Trust”), seeks to provide a combination of income and capital growth.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in certain funds in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates. More information about these and other discounts is available from your financial professional and in the “Details About the Share Classes” section on page 17 of the prospectus and in the “Purchase of Shares” section on page II-71 of the Statement of Additional Information (“SAI”).
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	May 1, 2013
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover:
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Master Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Master Portfolio’s portfolio turnover rate was 1,646% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	1646.00%
Expenses Deferred Charges [Text Block]	rr_ExpensesDeferredChargesTextBlock	A contingent deferred sales charge (“CDSC”) of 0.75% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in certain funds in the fund complex advised by BlackRock Advisors, LLC (“BlackRock”) or its affiliates.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	25,000
Expenses Represent Both Master and Feeder [Text]	rr_ExpensesRepresentBothMasterAndFeeder	The fees and expenses shown in the table above and the example that follows include the expenses of both the Fund and the Fund’s share of the allocated expenses of CoreAlpha Bond Master Portfolio (the “Master Portfolio”), a series of Master Investment Portfolio (“MIP”). Management fees are paid by the Master Portfolio.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Independent Expenses are based on estimated amounts for the current fiscal year.
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. 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:
Expense Example, No Redemption, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	You would pay the following expenses if you did not redeem your shares:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests, under normal circumstances, at least 80% of its assets in bonds. For the purposes of this strategy, “bonds” include the following: obligations issued or guaranteed by the U.S. government, its agencies or instrumentalities; mortgage-backed securities issued or guaranteed by the U.S. government or its agencies or instrumentalities, including U.S. agency mortgage pass-through securities; commercial mortgage-backed securities; debt obligations of U.S. issuers; municipal securities; asset-backed securities; and U.S.-registered dollar-denominated debt obligations of foreign issuers. The Fund may invest in bonds issued by companies located in countries other than the United States, including companies in emerging markets. These securities may have all types of interest rate payment and reset terms, including fixed rate, adjustable rate, floating rate, zero coupon, contingent, deferred, payment in kind and auction rate features. The Fund invests a substantial portion of its assets in U.S.-registered, dollar-denominated bonds. The Fund may invest up to 10% of its assets in securities rated below investment grade (“high yield” or “junk” bonds). The Fund may invest in bonds of any maturity or duration. The Fund may invest a significant portion of its assets in U.S. agency mortgage pass-through securities, which are securities issued by entities such as the Government National Mortgage Association (“Ginnie Mae”) and the Federal National Mortgage Association (“Fannie Mae”) that are backed by pools of mortgages. Most transactions in mortgage pass-through securities occur through standardized contracts for future delivery in which the exact mortgage-backed securities to be delivered are not specified until a few days prior to settlement. The Fund expects to enter into such contracts on a regular basis. The Fund may use derivatives, such as futures contracts, options and various other instruments. The Fund may also invest in derivatives based on foreign currencies. In addition, the Fund may use derivatives and short sales to enhance returns as part of an overall investment strategy or to offset a potential decline in the value of other holdings (commonly referred to as a “hedge”), although the Fund is not required to hedge and may choose not to do so. The Fund is a “feeder” fund that invests all of its investable assets in the Master Portfolio, which has the same investment objective and strategies as the Fund. All investments are made at the Master Portfolio level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of the Master Portfolio. For simplicity, the prospectus uses the name of the Fund or the term “Fund” (as applicable) to include the Master Portfolio.
Risk [Heading]	rr_RiskHeading	Principal Risks of Investing in the Fund
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund. Call Risk — Call risk is the risk that, during a period of falling interest rates, the issuer may redeem a security by repaying it early, which may reduce the Fund’s income if the proceeds are reinvested at lower interest rates. Debt Securities Risk — Debt securities, such as bonds, involve credit risk. Credit risk is the risk that the borrower will not make timely payments of principal and interest. 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 the issuer’s financial condition and on the terms of the securities. Debt securities are also subject to interest rate risk. Interest rate risk is the risk that the value of a debt security may fall when interest rates rise. In general, the market price of debt securities with longer maturities will go up or down more in response to changes in interest rates than the market price of shorter term securities. Derivatives Risk — The Fund’s use of derivatives may reduce the Fund’s returns and/or increase volatility. Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate perfectly with the overall securities markets. 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. Derivatives may give rise to a form of leverage and may expose the Fund to greater risk and increase its costs. Recent legislation calls for new regulation of the derivatives markets. The extent and impact of the regulation is not yet known and may not be known for some time. New regulation may make derivatives more costly, may limit the availability of derivatives, or may otherwise adversely affect the value or performance of derivatives. 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 securities markets have far lower trading volumes and less liquidity than developed markets. Extension Risk — When interest rates rise, certain obligations will be paid off by the obligor more slowly than anticipated, causing the value of these securities to fall. 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 may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries. — 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. Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that may cause income and principal losses for the Fund. Liquidity Risk — Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund’s investments in illiquid securities may reduce the returns of the Fund because it may be difficult to sell the illiquid securities at an advantageous time or price. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to liquidity risk. 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. 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. Mortgage- and Asset-Backed Securities Risks — Mortgage- and asset-backed securities represent interests in “pools” of mortgages or other assets, including consumer loans or receivables held in trust. Mortgage- and asset-backed securities are subject to credit, interest rate, prepayment and extension risks. These securities also are subject to risk of default on the underlying mortgage or asset, particularly during periods of economic downturn. Small movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain mortgage-backed securities. Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. Certain municipal securities, including private activity bonds, are not backed by the full faith, credit and taxing power of the issuer. Additionally, if events occur after the security is acquired that impact the security’s tax-exempt status, the Fund and its shareholders could be subject to substantial tax liabilities. 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. Short Sales Risk — Because making short sales in securities that it does not own exposes the Fund to the risks associated with those securities, such short sales involve speculative exposure risk. The Fund may incur a loss as a result of a short sale if the price of the security increases between the date of the short sale and the date on which the Fund replaces the borrowed security.
Risk Lose Money [Text]	rr_RiskLoseMoney	You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The Fund does not have a full calendar year of operations and Investor A and Investor C Shares commenced operations on May 1, 2012, therefore the chart and table are based on the performance of the Master Portfolio in which the Fund invests all of its assets for each complete calendar year since the commencement of the Master Portfolio’s operations, adjusted to reflect the estimated annual fund fees and operating expenses of each respective share class of the Fund. The Fund’s Institutional Shares would have substantially similar performance to the Investor A and Investor C Shares because the Institutional, Investor A and Investor C Shares are invested in the same portfolio of securities and performance would differ only to the extent that the share classes have different expenses. The actual return of Investor A Shares and Investor C Shares would have been lower than that of Institutional Shares because Investor A and Investor C Shares each have higher expenses than Institutional Shares. The table compares the performance to that of the Barclays U.S. Aggregate Bond Index. As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. If BlackRock and its affiliates had not waived or reimbursed certain Master Portfolio expenses during these periods, the Master Portfolio’s return would have been lower.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	The Fund does not have a full calendar year of operations and Investor A and Investor C Shares commenced operations on May 1, 2012, therefore the chart and table are based on the performance of the Master Portfolio in which the Fund invests all of its assets for each complete calendar year since the commencement of the Master Portfolio’s operations, adjusted to reflect the estimated annual fund fees and operating expenses of each respective share class of the Fund.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	As with all such investments, past performance (before and after taxes) is not an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Institutional Shares ANNUAL TOTAL RETURNS BlackRock CoreAlpha Bond Fund As of 12/31
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	Sales charges are not reflected in the bar chart. If they were, returns would be less than those shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the period shown in the bar chart, the highest return for a quarter was 5.78% (quarter ended September 30, 2009) and the lowest return for a quarter was -1.62% (quarter ended December 31, 2010). The year-to-date return as of September 30, 2012 was 4.34%.
Performance Table Heading	rr_PerformanceTableHeading	As of 12/31/11 Average Annual Total Returns
Performance Table Does Reflect Sales Loads	rr_PerformanceTableDoesReflectSalesLoads	However, the table includes all applicable fees and sales charges.
BlackRock CoreAlpha Bond Fund | Investor A Shares
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.00%
Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none	[1]
Management Fee	rr_ManagementFeesOverAssets	0.25%	[2],[3]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%	[2],[3]
Administration Fee	rr_Component1OtherExpensesOverAssets	0.20%	[2],[3]
Independent Expenses	rr_Component2OtherExpensesOverAssets	0.08%	[2],[3],[4],[5]
Other Expenses	rr_OtherExpensesOverAssets	0.28%	[2],[3]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[2],[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.79%	[2],[3]
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2],[3],[5]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.71%	[2],[3],[5]
1 Year	rr_ExpenseExampleYear01	470
3 Years	rr_ExpenseExampleYear03	635
5 Years	rr_ExpenseExampleYear05	814
10 Years	rr_ExpenseExampleYear10	1,332
1 Year	rr_AverageAnnualReturnYear01	3.66%
5 Years	rr_AverageAnnualReturnYear05	5.77%
Since Inception	rr_AverageAnnualReturnSinceInception	4.53%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 15, 2004
BlackRock CoreAlpha Bond Fund | Investor C Shares
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOfferingPrice	1.00%	[6]
Management Fee	rr_ManagementFeesOverAssets	0.25%	[2],[3]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%	[2],[3]
Administration Fee	rr_Component1OtherExpensesOverAssets	0.20%	[2],[3]
Independent Expenses	rr_Component2OtherExpensesOverAssets	0.08%	[2],[3],[4],[5]
Other Expenses	rr_OtherExpensesOverAssets	0.28%	[2],[3]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[2],[3]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.54%	[2],[3]
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2],[3],[5]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.46%	[2],[3],[5]
1 Year	rr_ExpenseExampleYear01	249
3 Years	rr_ExpenseExampleYear03	479
5 Years	rr_ExpenseExampleYear05	832
10 Years	rr_ExpenseExampleYear10	1,828
1 Year	rr_ExpenseExampleNoRedemptionYear01	149
3 Years	rr_ExpenseExampleNoRedemptionYear03	479
5 Years	rr_ExpenseExampleNoRedemptionYear05	832
10 Years	rr_ExpenseExampleNoRedemptionYear10	1,828
1 Year	rr_AverageAnnualReturnYear01	6.18%
5 Years	rr_AverageAnnualReturnYear05	5.84%
Since Inception	rr_AverageAnnualReturnSinceInception	4.29%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 15, 2004
BlackRock CoreAlpha Bond Fund | Institutional Shares
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Management Fee	rr_ManagementFeesOverAssets	0.25%	[2]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none	[2]
Administration Fee	rr_Component1OtherExpensesOverAssets	0.10%	[2]
Independent Expenses	rr_Component2OtherExpensesOverAssets	0.08%	[2],[4],[5]
Other Expenses	rr_OtherExpensesOverAssets	0.18%	[2]
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.01%	[2]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.44%	[2]
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.08%)	[2],[5]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.36%	[2],[5]
1 Year	rr_ExpenseExampleYear01	37
3 Years	rr_ExpenseExampleYear03	133
5 Years	rr_ExpenseExampleYear05	238
10 Years	rr_ExpenseExampleYear10	547
2005	rr_AnnualReturn2005	1.95%
2006	rr_AnnualReturn2006	4.34%
2007	rr_AnnualReturn2007	5.08%
2008	rr_AnnualReturn2008	3.60%
2009	rr_AnnualReturn2009	11.65%
2010	rr_AnnualReturn2010	6.54%
2011	rr_AnnualReturn2011	8.34%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	4.34%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.78%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(1.62%)
1 Year	rr_AverageAnnualReturnYear01	8.34%
5 Years	rr_AverageAnnualReturnYear05	7.01%
Since Inception	rr_AverageAnnualReturnSinceInception	5.44%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 15, 2004
BlackRock CoreAlpha Bond Fund | Barclays U.S. Aggregate Bond Index (Reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.84%
5 Years	rr_AverageAnnualReturnYear05	6.50%
Since Inception	rr_AverageAnnualReturnSinceInception	5.21%

[1] A contingent deferred sales charge ("CDSC") of 0.75% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more.

[2] The fees and expenses shown in the table above and the example that follows include the expenses of both the Fund and the Fund's share of the allocated expenses of CoreAlpha Bond Master Portfolio (the "Master Portfolio"), a series of Master Investment Portfolio ("MIP"). Management fees are paid by the Master Portfolio.

[3] These share classes commenced operations on May 1, 2012. Therefore the fees and expenses for these share classes are based on the Institutional Shares fees and expenses, restated to reflect the different fees and expenses applicable to these share classes.

[4] Independent Expenses are based on estimated amounts for the current fiscal year.

[5] Independent Expenses consist of the Fund's allocable portion of the fees and expenses of the independent trustees of the Trust and MIP, counsel to such independent trustees and the independent registered public accounting firm that provides audit and non-audit services to the Fund and the Master Portfolio. BlackRock has contractually agreed to reimburse, or provide offsetting credits to, the Fund and the Master Portfolio, as applicable, for Independent Expenses through April 30, 2013. After giving effect to such contractual arrangements, Independent Expenses will be 0.00%. Such contractual arrangement may not be terminated prior to May 1, 2013 without the consent of the Board of Trustees of the Trust and the Board of Trustees of MIP.

[6] There is no CDSC on Investor C Shares after one year.