BlackRock Emerging Market Local Debt Portfolio

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

BlackRock Funds II

Prospectus Date

rr_ProspectusDate

Apr. 27, 2012

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO

Objective, Primary [Text Block]

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Overview

Key Facts about BlackRock Emerging Market Local Debt Portfolio

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

rr_ObjectivePrimaryTextBlock

The BlackRock Emerging Market Local Debt Portfolio ("Emerging Market Local Debt Portfolio" or the "Fund") seeks maximum long term total return.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold 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 the BlackRock-advised fund complex. More information about these and other discounts is available from your financial professional and in the "Details about the Share Classes" section on page 40 of the Fund's prospectus and in the "Purchase of Shares" section on page II-69 of the Fund's statement of additional information.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees
(fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses

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 Fund 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 Fund's portfolio turnover rate was 195% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

195.00%

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 the BlackRock-advised fund complex. More information about these and other discounts is available from your financial professional and in the "Details about the Share Classes" section on page 40 of the Fund's prospectus and in the "Purchase of Shares" section on page II-69 of the Fund's statement of additional information.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

25,000

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The Total Annual Fund Operating Expenses do not correlate to the ratios of expenses to average net assets given in the Fund's most recent annual report which does not include the Acquired Fund Fees and Expenses.

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 BlackRock Emerging Market Local Debt Portfolio invests primarily in a global portfolio of fixed income securities and derivatives of any maturity of issuers located in emerging markets that may be denominated in any currency (on a hedged or un-hedged basis). Under normal circumstances, the Fund will invest at least 65% of its assets in fixed income securities and derivatives denominated in currencies of emerging market countries or whose value is tied in whole or in part to currencies of emerging market countries. Fixed income securities are debt obligations such as bonds and debentures, U.S. Government securities, debt obligations of domestic and non-U.S. corporations, debt obligations of non-U.S. governments and their political subdivisions, asset-backed securities, various mortgage-backed securities (both residential and commercial), other floating or variable rate obligations, municipal obligations and zero coupon debt securities. Emerging markets include, but are not limited to, countries that are included in the J.P. Morgan GBI-EM Global Diversified Index.

The Fund will invest at least 80% of its assets in fixed income securities issued by governments, their political subdivisions (states, provinces and municipalities), agencies and companies tied economically to an emerging market. Fund management considers securities to be tied economically to an emerging market if (1) the issuer is organized under the laws of or maintains its principal place of business in an emerging market country, (2) the issuer's securities are traded principally in an emerging market country or (3) the issuer, during its most recent fiscal year, derived at least 50% of its revenues or profits from goods produced or sold, investments made, or services performed in an emerging market country or has at least 50% of its assets in an emerging market country. The full spectrum of available investments, including non-investment grade (high yield or junk) securities (including distressed securities), securities of small cap issuers and derivatives may be utilized in satisfying the Fund's 80% policy. It is possible that up to 100% of the Fund's assets may be invested in non-investment grade (high yield or junk) securities. Many of the countries in which the Fund invests will have sovereign ratings that are below investment grade or will be unrated. The Fund may invest a significant portion of its assets in one country. The Fund may gain exposure to currencies by investing in bonds of emerging market issuers denominated in any currency. The Fund may also gain exposure to currencies through the use of cash and derivatives.

The management team may, when consistent with the Fund's investment objective, buy or sell options or futures, or enter into credit default swaps and interest rate or foreign currency transactions, including swaps (collectively, commonly known as derivatives). The Fund typically uses derivatives as a substitute for taking a position in the underlying asset and/or as part of a strategy designed to reduce exposure to other risks, such as interest rate or currency risk. The Fund may also use derivatives to enhance returns, in which case their use would involve leveraging risk. The Fund may seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts or by using other investment techniques (such as reverse repurchase agreements or dollar rolls, which involves a sale by a fund of a mortgage-backed or other security concurrently with an agreement by the fund to repurchase a similar security at a later date at an agreed-upon price).

The Fund may invest up to 10% of its assets in equity securities.

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.

Credit Risk — Credit risk refers to the possibility that the issuer of a security 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.

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.

Distressed Securities Risk — Distressed securities are speculative and involve substantial risks in addition to the risks of investing in junk bonds. The Fund will generally not receive interest payments on the distressed securities and may incur costs to protect its investment. In addition, distressed securities involve the substantial risk that principal will not be repaid. These securities may present a substantial risk of default or may be in default at the time of investment. The Fund may incur additional expenses to the extent it is required to seek recovery upon a default in the payment of principal of or interest on its portfolio holdings. In any reorganization or liquidation proceeding relating to a portfolio company, the Fund may lose its entire investment or may be required to accept cash or securities with a value less than its original investment. Distressed securities and any securities received in an exchange for such securities may be subject to restrictions on resale.

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.

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.

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.

Interest Rate Risk — 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.

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.

Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund's portfolio will be magnified when the Fund uses leverage.

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. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.

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.

Non-Diversification Risk — The Fund is a non-diversified fund. Because the Fund may invest in securities of a smaller number of issuers, it may be more exposed to the risks associated with and developments affecting an individual issuer than a fund that invests more widely.

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.

Risks of Concentrating in One Country — Investing a significant portion of assets in one country makes the Fund more dependent upon the political and economic circumstances of that particular country than a mutual fund that is more widely diversified.

Small Cap and Emerging Growth Securities Risk — Small cap or emerging growth companies may have limited product lines or markets. They may be less financially secure than larger, more established companies. They may depend on a more limited management group than larger capitalized companies.

Sovereign Debt Risk — Sovereign debt instruments are subject to the risk that a governmental entity may delay or refuse to pay interest or repay principal on its sovereign debt, due, for example, to cash flow problems, insufficient foreign currency reserves, political considerations, the relative size of the governmental entity's debt position in relation to the economy or the failure to put in place economic reforms required by the International Monetary Fund or other multilateral agencies.

Zero Coupon Securities Risk — While interest payments are not made on such securities, holders of such securities are deemed to have received income ("phantom income") annually, notwithstanding that cash may not be received currently. The effect of owning instruments that do not make current interest payments is that a fixed yield is earned not only on the original investment but also, in effect, on all discount accretion during the life of the obligations. This implicit reinvestment of earnings at a fixed rate eliminates the risk of being unable to invest distributions at a rate as high as the implicit yield on the zero coupon bond, but at the same time eliminates the holder's ability to reinvest at higher rates in the future. For this reason, some of these securities may be subject to substantially greater price fluctuations during periods of changing market interest rates than are comparable securities that pay interest currently. Longer term zero coupon bonds are more exposed to interest rate risk than shorter term zero coupon bonds. These investments benefit the issuer by mitigating its need for cash to meet debt service, but also require a higher rate of return to attract investors who are willing to defer receipt of cash.

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.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Non-Diversification Risk — The Fund is a non-diversified fund. Because the Fund may invest in securities of a smaller number of issuers, it may be more exposed to the risks associated with and developments affecting an individual issuer than a fund that invests more widely.

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's Annual Total Returns prior to September 3, 2012 as reflected in the bar chart and the table are the returns of the Fund that followed different investment strategies under the name "BlackRock Emerging Market Debt Portfolio." The table compares the Fund's performance to that of the J.P. Morgan EMBI Global Index and the J.P. Morgan GBI-EM Global Diversified Index. Effective September 3, 2012, the Fund's benchmark against which it measures its performance, the J.P. Morgan EMBI Global Index, was replaced with the J.P. Morgan GBI-EM Global Diversified Index, a broad measure of market performance. Fund management believes the J.P. Morgan GBI-EM Global Diversified Index is more relevant to the Fund's current investment strategies. The J.P. Morgan GBI-EM Global Diversified Index is an unmanaged index that tracks local currency bonds. 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 the Fund's investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund's returns would have been lower. Updated information on the Fund's performance can be obtained by visiting http://www.blackrock.com/funds or can be obtained by phone at 800-882-0052.

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 Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800-882-0052

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

http://www.blackrock.com/funds

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

Investor A Shares
ANNUAL TOTAL RETURNS
Emerging Market Local Debt Portfolio
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 10.06% (quarter ended June 30, 2009) and the lowest return for a quarter was –2.44% (quarter ended September 30, 2011). The year-to-date return as of March 31, 2012 was 4.92%.

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.

Performance Table Market Index Changed

rr_PerformanceTableMarketIndexChanged

Effective September 3, 2012, the Fund's benchmark against which it measures its performance, the J.P. Morgan EMBI Global Index, was replaced with the J.P. Morgan GBI-EM Global Diversified Index, a broad measure of market performance. Fund management believes the J.P. Morgan GBI-EM Global Diversified Index is more relevant to the Fund's current investment strategies. The J.P. Morgan GBI-EM Global Diversified Index is an unmanaged index that tracks local currency bonds.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual Federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on the investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Investor A Shares only, and the after-tax returns for Investor C and Institutional Shares will vary.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using the historical highest individual Federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Investor C and Institutional Shares will vary.

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO | Investor A Shares

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

4.00%

Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)

rr_MaximumDeferredSalesChargeOverOther

none

^[1]

Management Fee

rr_ManagementFeesOverAssets

0.60%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.66%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.52%

^[2]

Fee Waivers and Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

^[3]

Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.26%

^[3]

rr_ExpenseExampleYear01

523

rr_ExpenseExampleYear03

837

rr_ExpenseExampleYear05

1,172

Year to Date Return, Label

rr_ExpenseExampleYear10

2,119

2009

rr_AnnualReturn2009

23.75%

2010

rr_AnnualReturn2010

11.02%

2011

rr_AnnualReturn2011

4.81%

rr_YearToDateReturnLabel

The year-to-date return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

4.92%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

the highest return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

10.06%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

the lowest return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.44%)

rr_AverageAnnualReturnYear01

0.61%

rr_AverageAnnualReturnSinceInception

5.16%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 01, 2008

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO | Investor C Shares

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[4]

Management Fee

rr_ManagementFeesOverAssets

0.60%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.65%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.26%

^[2]

Fee Waivers and Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.25%)

^[3]

Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements

rr_NetExpensesOverAssets

2.01%

^[3]

rr_ExpenseExampleYear01

304

rr_ExpenseExampleYear03

682

rr_ExpenseExampleYear05

1,187

rr_ExpenseExampleYear10

2,576

rr_ExpenseExampleNoRedemptionYear01

204

rr_ExpenseExampleNoRedemptionYear03

682

rr_ExpenseExampleNoRedemptionYear05

1,187

rr_ExpenseExampleNoRedemptionYear10

2,576

rr_AverageAnnualReturnYear01

2.98%

rr_AverageAnnualReturnSinceInception

5.49%

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO | Institutional Shares

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_RiskReturnAbstract

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fee

rr_ManagementFeesOverAssets

0.60%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.60%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[2]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.21%

^[2]

Fee Waivers and Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.20%)

^[3]

Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements

rr_NetExpensesOverAssets

1.01%

^[3]

rr_ExpenseExampleYear01

103

rr_ExpenseExampleYear03

364

rr_ExpenseExampleYear05

646

rr_ExpenseExampleYear10

1,448

rr_AverageAnnualReturnYear01

5.11%

rr_AverageAnnualReturnSinceInception

6.57%

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO | Return After Taxes on Distributions | Investor A Shares

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

(0.98%)

rr_AverageAnnualReturnSinceInception

3.26%

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO | Return After Taxes on Distributions and Sale of Shares | Investor A Shares

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

0.43%

rr_AverageAnnualReturnSinceInception

3.27%

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO | J.P. Morgan EMBI Global Index (Reflects no deduction for fees, expenses or taxes)

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

8.46%

rr_AverageAnnualReturnSinceInception

8.46%

Class A, C, Institutional | BLACKROCK EMERGING MARKET LOCAL DEBT PORTFOLIO | J.P. Morgan GBI-EM Global Diversified Index (Reflects no deduction for fees, expenses or taxes)

rr_RiskReturnAbstract

rr_AverageAnnualReturnYear01

(1.75%)