2.2.0.25truefalse000101 - Document - Risk/Return Summary {Unlabeled} - BLACKROCK INDEX EQUITY PORTFOLIOfalsefalsetrue1falsefalseUSDtruefalse{dei_DocumentInformationDocumentAxis} : Investor B C Institutional Member {dei_LegalEntityAxis} : S000001513 Member 4/29/2011 - 4/29/2011 USD ($) $Duration_4_29_2011_To_4_29_2011_dei_DocumentInformationDocumentAxis_cik000844779_InvestorBCInstitutionalMember_dei_LegalEntityAxis_cik000844779_S000001513Memberhttp://www.sec.gov/CIK0000844779duration2011-04-29T00:00:002011-04-29T00:00:00falsefalsecik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalsecik000844779_S000001513Memberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberUnit1Standardhttp://www.xbrl.org/2003/instancepurexbrli0Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.blackrock.com/role/documentriskreturnsummaryunlabeledblackrockindexequityportfolio1falsefalsefalse00Investor A, B, C, Institutional | BLACKROCK INDEX EQUITY PORTFOLIOInvestor A, B, C, Institutional | BLACKROCK INDEX EQUITY PORTFOLIOfalsefalsefalsefalsefalse1falsefalseUSDtruefalse{dei_DocumentInformationDocumentAxis} : Investor B C Institutional Member {dei_LegalEntityAxis} : S000001513 Member 4/29/2011 - 4/29/2011 USD ($) $Duration_4_29_2011_To_4_29_2011_dei_DocumentInformationDocumentAxis_cik000844779_InvestorBCInstitutionalMember_dei_LegalEntityAxis_cik000844779_S000001513Memberhttp://www.sec.gov/CIK0000844779duration2011-04-29T00:00:002011-04-29T00:00:00falsefalsecik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalsecik000844779_S000001513Memberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberUnit1Standardhttp://www.xbrl.org/2003/instancepurexbrli0Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseInvestor A, B, C, Institutional | BLACKROCK INDEX EQUITY PORTFOLIO3false0rr_RiskReturnHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 30pt;" class="_mt">Fund Overview</font></p> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 12pt;" class="_mt"><b>Key Facts About BlackRock Index Equity Portfolio</b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Summary Investment Objectives/Goals Include the following information, in plain English under rule 421(d) under the Securities Act, in the order and subject matter indicatedReference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 falsefalseRisk/Return [Heading]4false0rr_ObjectiveHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 12pt;" class="_mt"><b><i>Investment Objective</i></b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseObjective [Heading]5false0rr_ObjectivePrimaryTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">The investment objective of BlackRock Index Equity Portfolio ("Index Equity Portfolio" or the "Fund"), a series of BlackRock Funds^SM (the "Trust"), is to match the performance of the Standard &amp; Poor's</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"> 500 Index (the "S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">") as closely as possible before the deduction of Fund expenses.</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseObjective, Primary [Text Block]6false0rr_ExpenseHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 12pt;" class="_mt"><b><i>Fees and Expenses of the Fund</i></b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Summary Fee Table Includes the following information, in plain English under rule 421(d) under the Securities Act, after Item 2 Fees and expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shared 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 $[_____] in [name of fund family] funds. Shareholder Fees (fees paid directly from your investment) Example 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 you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be You would pay the following expenses if you did not redeem your shares The Example does not reflect sales charges (loads) on reinvested dividends [and other distributions]. If these sales charges (loads) were included, your costs would be higher. Portfolio Turnover 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. 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 __% of the average value of its whole portfolio. Instructions. A.3.instructions.6 New Funds. For purposes of this Item, a "New Fund" is a Fund that does not include in Form N-1A financial statements reporting operating results or that includes financial statements for the Fund's initial fiscal year reporting operating results for a period of 6 months or less. The following Instructions apply to New Funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph d -Subsection instructions falsefalseExpense [Heading]7false0rr_ExpenseNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">This table describes the fees and expenses that you may pay if you buy and hold shares of Index Equity Portfolio.&nbsp;<font class="_mt">You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least&nbsp;<font class="_mt">$<font class="_mt">50,000</font></font> in the fund complex advised by BlackRock Advisors, LLC ("BlackRock") </font>. More information about these and other discounts is available from your financial professional and in the "Details About the Share Classes" section on page 14 of the Fund's prospectus and in the "Purchase of Shares" section on page II-57 of the Fund's statement of additional information.</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThis table describes the fees and expenses that you may pay if you buy and hold shared 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 $[_____] in [name of fund family] funds. Include the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown.The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount. 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If a sales charge (load) is imposed on shares purchased with reinvested capital gains distributions or returns of capital, include the bracketed words in the third caption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection table falsefalseMaximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)0rr_MaximumCumulativeSalesChargeOverOfferingPricetruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.030.03falsefalsefalsetruefalse2truetruetrue00falsefalsefalsetruefalse3truetruetrue00falsefalsefalsetruefalse4truetruetrue00falsefalsefalsetruefalseOthernanafalsefalseMaximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)2falseRowprimaryElement*6false0rr_MaximumDeferredSalesChargeOverOfferingPricerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truetruetrue00falsefalsefalsetruefalse2truetruetrue00falsefalsefalsetruefalse3truetruetrue0.0450.045[1]falsefalsefalsetruefalse4truetruetrue0.010.01[2]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. 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SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*5false0rr_ManagementFeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truetruetrue0.00010.0001[1],[3]falsefalsefalsetruefalse2truetruetrue0.00010.0001[1],[3]falsefalsefalsetruefalse3truetruetrue0.00010.0001[1],[3]falsefalsefalsetruefalse4truetruetrue0.00010.0001[1],[3]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureManagement Fees include investment advisory fees (including any fees based on the Fund's performance), any other management fees payable to the investment adviser or its affiliates, and administrative fees payable to the investment adviser or its affiliates that are not included as "Other Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph a -Subsection instructions falsefalseManagement Fee0rr_ManagementFeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[1][2]1truetruetrue0.00010.0001falsefalsefalsetruefalse2truetruetrue0.00010.0001falsefalsefalsetruefalse3truetruetrue0.00010.0001falsefalsefalsetruefalse4truetruetrue0.00010.0001falsefalsefalsetruefalseOthernanafalsefalseManagement Fee2falseRowprimaryElement*6false0rr_DistributionAndService12b1FeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.000.00[3]falsefalsefalsetruefalse2truetruetrue0.00150.0015[3]falsefalsefalsetruefalse3truetruetrue0.00900.0090[3]falsefalsefalsetruefalse4truetruetrue0.00900.0090[3]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureDistribution [and/or Service] (12b-1) Fees" include all distribution or other expenses incurred during the most recent fiscal year under a plan adopted pursuant to rule 12b-1 [17 CFR 270.12b-1]. Under an appropriate caption or a subcaption of "Other Expenses," disclose the amount of any distribution or similar expenses deducted from the Fund's assets other than pursuant to a rule 12b-1 plan.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 9 -Subsection table falsefalseDistribution and/or Service (12b-1) Fees0rr_DistributionAndService12b1FeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2]1truetruetrue0.00150.0015falsefalsefalsetruefalse2truetruetrue0.00900.0090falsefalsefalsetruefalse3truetruetrue0.00900.0090falsefalsefalsetruefalse4truetruetrue0.000.00falsefalsefalsetruefalseOthernanafalsefalseDistribution and/or Service (12b-1) Fees3falseRowprimaryElement*7false0rr_OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truetruetrue0.002150.00215[3]falsefalsefalsetruefalse2truetruetrue0.002650.00265[3]falsefalsefalsetruefalse3truetruetrue0.004450.00445[3]falsefalsefalsetruefalse4truetruetrue0.003450.00345[3]falsefalsefalsetruefalseOtherrr:NonNegativePure4Typepure"Other Expenses" include all expenses not otherwise disclosed in the table that are deducted from the Fund's assets or charged to all shareholder accounts. The amount of expenses deducted from the Fund's assets are the amounts shown as expenses in the Fund's statement of operations (including increases resulting from complying with paragraph 2(g) of rule 6-07 of Regulation S-X [17 CFR 210.6-07]). "Other Expenses" do not include extraordinary expenses as determined under generally accepted accounting principles (see Accounting Principles Board Opinion No. 30). If extraordinary expenses were incurred that materially affected the Fund's "Other Expenses," disclose in a footnote to the table what "Other Expenses" would have been had the extraordinary expenses been included.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph c -Clause i -Subsection instructions truefalseOther Expenses0rr_OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2]1truetruetrue0.002650.00265falsefalsefalsetruefalse2truetruetrue0.004450.00445falsefalsefalsetruefalse3truetruetrue0.003450.00345falsefalsefalsetruefalse4truetruetrue0.002150.00215falsefalsefalsetruefalseOthernanafalsefalseOther Expenses4falseRowprimaryElement*8false0rr_Component1OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.001000.00100[2],[3]falsefalsefalsetruefalse2truetruetrue0.001000.00100[2],[3]falsefalsefalsetruefalse3truetruetrue0.001000.00100[2],[3]falsefalsefalsetruefalse4truetruetrue0.001000.00100[2],[3]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureThe Fund may subdivide this caption into no more than three subcaptions that identify the largest expense or expenses comprising "Other Expenses," but must include a total of all "Other Expenses." Alternatively, the Fund may include the components of "Other Expenses" in a parenthetical to the caption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph c -Clause iii -Subsection instructions falsefalseAdministration Fees0rr_Component1OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2][3]1truetruetrue0.001000.00100falsefalsefalsetruefalse2truetruetrue0.001000.00100falsefalsefalsetruefalse3truetruetrue0.001000.00100falsefalsefalsetruefalse4truetruetrue0.001000.00100falsefalsefalsetruefalseOthernanafalsefalseAdministration Fees5falseRowprimaryElement*9false0rr_Component2OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.001150.00115[3]falsefalsefalsetruefalse2truetruetrue0.001650.00165[3]falsefalsefalsetruefalse3truetruetrue0.003450.00345[3]falsefalsefalsetruefalse4truetruetrue0.002450.00245[3]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureThe Fund may subdivide this caption into no more than three subcaptions that identify the largest expense or expenses comprising "Other Expenses," but must include a total of all "Other Expenses." Alternatively, the Fund may include the components of "Other Expenses" in a parenthetical to the caption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 10 -Subsection table falsefalseMiscellaneous Other Expense0rr_Component2OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2]1truetruetrue0.001650.00165falsefalsefalsetruefalse2truetruetrue0.003450.00345falsefalsefalsetruefalse3truetruetrue0.002450.00245falsefalsefalsetruefalse4truetruetrue0.001150.00115falsefalsefalsetruefalseOthernanafalsefalseMiscellaneous Other Expense6falseRowprimaryElement*10false0rr_ExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truetruetrue0.002250.00225[3]falsefalsefalsetruefalse2truetruetrue0.004250.00425[3]falsefalsefalsetruefalse3truetruetrue0.013550.01355[3]falsefalsefalsetruefalse4truetruetrue0.012550.01255[3]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses. If the Fund is a Feeder Fund, reflect the aggregate expenses of the Feeder Fund and the Master Fund in a single fee table using the captions provided. In a footnote to the fee table, state that the table and Example reflect the expenses of both the Feeder and Master Funds. If the prospectus offers more than one Class of a Multiple Class Fund or more than one Feeder Fund that invests in the same Master Fund, provide a separate response for each Class or Feeder Fund. Base the percentages of "Annual Fund Operating Expenses" on amounts incurred during the Fund's most recent fiscal year, but include in expenses amounts that would have been incurred absent expense reimbursement or fee waiver arrangements. If the Fund has changed its fiscal year and, as a result, the most recent fiscal year is less than three months, use the fiscal year prior to the most recent fiscal year as the basis for determining "Annual Fund Operating Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph d -Subsection instructions truefalseTotal Annual Fund Operating Expenses0rr_ExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[2]1truetruetrue0.004250.00425falsefalsefalsetruefalse2truetruetrue0.013550.01355falsefalsefalsetruefalse3truetruetrue0.012550.01255falsefalsefalsetruefalse4truetruetrue0.002250.00225falsefalsefalsetruefalseOthernanafalsefalseTotal Annual Fund Operating Expenses7falseRowprimaryElement*11false0rr_FeeWaiverOrReimbursementOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue-0.00045-0.00045[1],[2],[3]falsefalsefalsetruefalse2truetruetrue-0.00005-0.00005[1],[2],[3]falsefalsefalsetruefalse3truetruetrue-0.00115-0.00115[1],[2],[3]falsefalsefalsetruefalse4truetruetrue-0.00015-0.00015[1],[2],[3]falsefalsefalsetruefalseOtherrr:NonPositivePure4TypepureTotal Annual Fund Operating Expenses. If there were expense reimbursement or fee waiver arrangements that reduced any Fund operating expenses and will continue to reduce them for no less than one year from the effective date of the Fund's registration statement, a Fund may add two captions to the table one caption showing the amount of the expense reimbursement or fee waiver, and a second caption showing the Fund's net expenses after subtracting the fee reimbursement or expense waiver from the total fund operating expenses. The Fund should place these additional captions directly below the "Total Annual Fund Operating Expenses" caption of the table and should use appropriate descriptive captions, such as "Fee Waiver [and/or Expense Reimbursement]" and "Total Annual Fund Operating Expenses After Fee Waiver [and/or Expense Reimbursement]," respectively. If the Fund provides this disclosure, also disclose the period for which the expense reimbursement or fee waiver arrangement is expected to continue, and briefly describe who can terminate the arrangement and under what circumstances.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 11 -Subsection table falsefalseFee Waivers and/or Expense Reimbursements0rr_FeeWaiverOrReimbursementOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[1][2][3]1truetruetrue-0.00005-0.00005falsefalsefalsetruefalse2truetruetrue-0.00115-0.00115falsefalsefalsetruefalse3truetruetrue-0.00015-0.00015falsefalsefalsetruefalse4truetruetrue-0.00045-0.00045falsefalsefalsetruefalseOthernanafalsefalseFee Waivers and/or Expense Reimbursements8falseRowprimaryElement*12false0rr_NetExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truetruetrue0.00180.0018[1],[2],[3]falsefalsefalsetruefalse2truetruetrue0.00420.0042[1],[2],[3]falsefalsefalsetruefalse3truetruetrue0.01240.0124[1],[2],[3]falsefalsefalsetruefalse4truetruetrue0.01240.0124[1],[2],[3]falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 11 -Subsection table truefalseTotal Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements0rr_NetExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[1][2][3]1truetruetrue0.00420.0042falsefalsefalsetruefalse2truetruetrue0.01240.0124falsefalsefalsetruefalse3truetruetrue0.01240.0124falsefalsefalsetruefalse4truetruetrue0.00180.0018falsefalsefalsetruefalseOthernanafalsefalseTotal Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements1As described in the "Management of the Fund" section of the Fund's prospectus on pages 28&ndash;33, BlackRock has contractually agreed to waive and/or reimburse fees and/or expenses in order to ensure that management fees payable by the Series will not exceed 0.005% of average daily net assets until May 1, 2012. This agreement may be terminated upon 90 days' notice by a majority of the non-interested directors of Quantitative Master Series LLC or by a vote of a majority of the outstanding voting securities of the Series.2The fees and expenses shown in the table and the example that follows include both the expenses of the Fund and the Fund's share of the allocated expenses of the Master S&amp;P 500 Index Series (the "Series"). Management fees are paid by the Series.3As described in the "Management of the Fund" section of the Fund's prospectus on pages 28&ndash;33, BlackRock has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) as a percentage of average daily net assets to 0.785% (for Investor A Shares), 1.24% (for Investor B and C Shares) and 0.18% (for Institutional Shares) until May 1, 2012. The Fund may have to repay some of these waivers and reimbursements to BlackRock in the following two years. The agreement may be terminated upon 90 days' notice by a majority of the non-interested trustees of the Trust or by vote of a majority of the outstanding voting securities of the Fund.48Annual Fund Operating Expenses - Investor A, B, C, Institutional BLACKROCK INDEX EQUITY PORTFOLIOUnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberColumndei_LegalEntityAxisAxiscik000844779_S000001513MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to OperatingExpensesData.No authoritative reference available.falsefalseAnnual Fund Operating Expenses [Table]12false0rr_ExpenseExampleHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 11pt;" class="_mt"><b>Example:</b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringHeading for Expense Example.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalseExpense Example [Heading]13false0rr_ExpenseExampleNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">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:</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThe Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection example falsefalseExpense Example Narrative [Text Block]14false0rr_ExpenseExampleWithRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposedBlackrockIndexEquityPortfolio row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvestorBCInstitutionalMember column dei_LegalEntityAxis compact cik000844779_S000001513Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposedBlackrockIndexEquityPortfolio row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvestorBCInstitutionalMember column dei_LegalEntityAxis compact cik000844779_S000001513Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>truehttp://www.blackrock.com/role/ScheduleExpenseExampleTransposedBlackrockIndexEquityPortfoliofalsefalse000104 - Schedule - Expense Example {Transposed} - {BLACKROCK INDEX EQUITY PORTFOLIO}truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*5false0rr_ExpenseExampleYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue1818falsefalsefalsetruefalse2truefalsetrue342342falsefalsefalsetruefalse3truefalsetrue576576falsefalsefalsetruefalse4truefalsetrue226226falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalse1 Yearduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_ExpenseExampleYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue6868falsefalsefalsetruefalse2truefalsetrue432432falsefalsefalsetruefalse3truefalsetrue768768falsefalsefalsetruefalse4truefalsetrue397397falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse3 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_ExpenseExampleYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue122122falsefalsefalsetruefalse2truefalsetrue531531falsefalsefalsetruefalse3truefalsetrue931931falsefalsefalsetruefalse4truefalsetrue688688falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse5 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*8false0rr_ExpenseExampleYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue282282falsefalsefalsetruefalse2truefalsetrue820820falsefalsefalsetruefalse3truefalsetrue13631363falsefalsefalsetruefalse4truefalsetrue15161516falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse10 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004080Memberrr_ProspectusShareClassAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor A SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue342342falsefalsefalsetruefalse2truefalsetrue432432falsefalsefalsetruefalse3truefalsetrue531531falsefalsefalsetruefalse4truefalsetrue820820falsefalsefalsetruefalseOthernanafalsefalseInvestor A Shares2falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor B Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004081Memberrr_ProspectusShareClassAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor B SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue576576falsefalsefalsetruefalse2truefalsetrue768768falsefalsefalsetruefalse3truefalsetrue931931falsefalsefalsetruefalse4truefalsetrue13631363falsefalsefalsetruefalseOthernanafalsefalseInvestor B Shares3falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor C Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004082Memberrr_ProspectusShareClassAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor C SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue226226falsefalsefalsetruefalse2truefalsetrue397397falsefalsefalsetruefalse3truefalsetrue688688falsefalsefalsetruefalse4truefalsetrue15161516falsefalsefalsetruefalseOthernanafalsefalseInvestor C Shares4falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInstitutional Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004078Memberrr_ProspectusShareClassAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInstitutional SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue1818falsefalsefalsetruefalse2truefalsetrue6868falsefalsefalsetruefalse3truefalsetrue122122falsefalsefalsetruefalse4truefalsetrue282282falsefalsefalsetruefalseOthernanafalsefalseInstitutional Shares44Expense Example - Investor A, B, C, Institutional BLACKROCK INDEX EQUITY PORTFOLIO (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExample.No authoritative reference available.falsefalseExpense Example, With Redemption [Table]15false0rr_ExpenseExampleNoRedemptionNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">You would pay the following expenses if you did not redeem your shares:</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExampleNoRedemption.No authoritative reference available.falsefalseExpense Example, No Redemption Narrative [Text Block]16false0rr_ExpenseExampleNoRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleExpenseExampleNoRedemptionTransposedBlackrockIndexEquityPortfolio row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvestorBCInstitutionalMember column dei_LegalEntityAxis compact cik000844779_S000001513Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleExpenseExampleNoRedemptionTransposedBlackrockIndexEquityPortfolio row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvestorBCInstitutionalMember column dei_LegalEntityAxis compact cik000844779_S000001513Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>truehttp://www.blackrock.com/role/ScheduleExpenseExampleNoRedemptionTransposedBlackrockIndexEquityPortfoliofalsefalse000105 - Schedule - Expense Example, No Redemption {Transposed} - {BLACKROCK INDEX EQUITY PORTFOLIO}truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*5false0rr_ExpenseExampleNoRedemptionYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue126126falsefalsefalsetruefalse2truefalsetrue126126falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalse1 Yearduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_ExpenseExampleNoRedemptionYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue418418falsefalsefalsetruefalse2truefalsetrue397397falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph 1 -Subsection example falsefalse3 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_ExpenseExampleNoRedemptionYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue731731falsefalsefalsetruefalse2truefalsetrue688688falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subparagraph f -Subsection instructions falsefalse5 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*8false0rr_ExpenseExampleNoRedemptionYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue13631363falsefalsefalsetruefalse2truefalsetrue15161516falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subparagraph f -Subsection instructions falsefalse10 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor B Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004081Memberrr_ProspectusShareClassAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor B SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue126126falsefalsefalsetruefalse2truefalsetrue418418falsefalsefalsetruefalse3truefalsetrue731731falsefalsefalsetruefalse4truefalsetrue13631363falsefalsefalsetruefalseOthernanafalsefalseInvestor B Shares2falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor C Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004082Memberrr_ProspectusShareClassAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor C SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue126126falsefalsefalsetruefalse2truefalsetrue397397falsefalsefalsetruefalse3truefalsetrue688688falsefalsefalsetruefalse4truefalsetrue15161516falsefalsefalsetruefalseOthernanafalsefalseInvestor C Shares42Expense Example, No Redemption - Investor A, B, C, Institutional BLACKROCK INDEX EQUITY PORTFOLIO (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExampleNoRedemption.No authoritative reference available.falsefalseExpense Example, No Redemption [Table]17false0rr_PortfolioTurnoverHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 11pt;" class="_mt"><b>Portfolio Turnover:</b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 5 -Subsection instructions falsefalsePortfolio Turnover [Heading]18false0rr_PortfolioTurnoverTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">The Series 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 Series' portfolio turnover rate was&nbsp;<font class="_mt">5%</font> of the average value of its portfolio.</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subsection example falsefalsePortfolio Turnover [Text Block]19false0rr_StrategyHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 12pt;" class="_mt"><b><i>Principal Investment Strategies of the Fund</i></b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a falsefalseStrategy [Heading]20false0rr_StrategyNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">Index Equity Portfolio employs a "passive" management approach, attempting to invest in a portfolio of assets whose performance is expected to match approximately the performance of the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">. <font class="_mt"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">The Fund will be substantially invested in securities in the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">, and will invest, under normal circumstances, at least 80% of its assets in securities or other financial instruments that are components of or have economic characteristics similar to the securities included in the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font></font></font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">. The Fund may change its target index if Fund management believes a different index would better enable the Fund to match the performance of the market segment represented by the current index.</font></p> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">The Fund will invest in the common stocks represented in the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"> in roughly the same proportions as their weightings in the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">. The Fund may also invest in derivative instruments linked to the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">. At times, the Fund may not invest in all of the common stocks in the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">, or in the same weightings as in the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">. At those times, the Fund chooses investments so that the market capitalizations, industry weighting and other investment characteristics of the stocks and derivative instruments chosen are similar to the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"> as a whole.</font></p> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">The Fund is a "feeder fund" that invests all of its assets in the Master S&amp;P 500 Index Series (previously defined as the "Series") of Quantitative Master Series LLC (the "Master LLC") which has the same investment objective and strategies as the Fund. All investments are made at the Series level. This structure is sometimes called a "master/feeder" structure. The Fund's investment results will correspond directly to the investment results of the Series. For simplicity, this prospectus uses the term "Index Equity Portfolio" or "Fund" to include, where applicable, the Series.</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a falsefalseStrategy Narrative [Text Block]21false0rr_RiskHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 12pt;" class="_mt"><b><i>Principal Risks of Investing in the Fund</i></b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNarrative Risk Disclosure.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subsection b falsefalseRisk [Heading]22false0rr_RiskNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">Risk is inherent in all investing. The value of your investment in Index Equity Portfolio, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time.<font class="_mt">You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments</font>. The following is a summary description of certain risks of investing in the Fund.</font></p> <p align="left"><font style="font-family: Wingdings; font-size: 10pt;" class="_mt">n</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">&nbsp;&nbsp;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"><b><i>Equity Securities Risk</i></b></font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"> &#8212; 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.</font></p> <p align="left"><font style="font-family: Wingdings; font-size: 10pt;" class="_mt">n</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">&nbsp;&nbsp;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"><b><i>Index Fund Risk</i></b></font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"> &#8212; An index fund has operating and other expenses while an index does not. As a result, while the Fund will attempt to track the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"> as closely as possible, it will tend to underperform the index to some <font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">degree over time. If an index fund is properly correlated to its stated index, the Fund will perform poorly when the index performs poorly.</font></font></p> <div> <p align="left"><font style="font-family: Wingdings; font-size: 10pt;" class="_mt">n</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">&nbsp;&nbsp;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"><b><i>Market Risk and Selection Risk</i></b></font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"> &#8212; 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.</font></p></div></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringNarrative Risk Disclosure. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subparagraph i -Clause instruction -Subsection b falsefalseRisk Narrative [Text Block]23false0rr_BarChartAndPerformanceTableHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 12pt;" class="_mt"><b><i>Performance Information</i></b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalseBar Chart and Performance Table [Heading]24false0rr_PerformanceNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"><font class="_mt"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">The information shows you how Index Equity Portfolio's performance has varied year by year and provides some indication of the risks of investing in the Fund</font></font>. The table compares the Fund's performance to that of the S&amp;P 500</font><font style="font-family: Arial, Helvetica; font-size: 5pt;" class="_mt">^&#174;</font><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">. <font class="_mt">As with all such investments, past performance (before and after taxes) is not an indication of future results</font>. <font class="_mt">Sales charges are not reflected in the bar chart</font>. 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 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&nbsp;<font class="_mt"><a href="funds">www.blackrock.com/funds</a></font> or can be obtained by phone at <font class="_mt">(800) 882-0052</font>.</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalsePerformance Narrative [Text Block]25false0rr_BarChartHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p align="center"><font style="font-family: Arial, Helvetica; font-size: 11pt;" class="_mt"><b>Investor A Shares<br />ANNUAL TOTAL RETURNS<br />BlackRock Index Equity Portfolio<br />As of 12/31</b></font></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalseBar Chart [Heading]26false0rr_BarChartTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleAnnualTotalReturnsBlackrockIndexEquityPortfolioBarChart column period compact * column primary compact * row dei_DocumentInformationDocumentAxis compact cik000844779_InvestorBCInstitutionalMember row dei_LegalEntityAxis compact cik000844779_S000001513Member row rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsefalseBarChart1.jpg<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleAnnualTotalReturnsBlackrockIndexEquityPortfolioBarChart column period compact * column primary compact * row dei_DocumentInformationDocumentAxis compact cik000844779_InvestorBCInstitutionalMember row dei_LegalEntityAxis compact cik000844779_S000001513Member row rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsehttp://www.blackrock.com/role/ScheduleAnnualTotalReturnsBlackrockIndexEquityPortfolioBarChartfalsefalse000106 - Schedule - Annual Total Returns - {BLACKROCK INDEX EQUITY PORTFOLIO}[Bar Chart]truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*5false0rr_AnnualReturn2001rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.1268-0.1268falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. 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Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. 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Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. 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Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. 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Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2005duration2011-04-29T00:00:002011-04-29T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$6falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*10false0rr_AnnualReturn2006rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.15510.1551falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2006duration2011-04-29T00:00:002011-04-29T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$7falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*11false0rr_AnnualReturn2007rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.05230.0523falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 2007duration2011-04-29T00:00:002011-04-29T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$8falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*12false0rr_AnnualReturn2008rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.3721-0.3721falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2008duration2011-04-29T00:00:002011-04-29T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$9falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*13false0rr_AnnualReturn2009rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.26080.2608falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 2009duration2011-04-29T00:00:002011-04-29T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$10falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*14false0rr_AnnualReturn2010rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.14640.1464falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2010duration2011-04-29T00:00:002011-04-29T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004080Memberrr_ProspectusShareClassAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor A Shares0truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.1268-0.1268falsefalsefalsetruefalse2truetruefalse-0.2207-0.2207falsefalsefalsetruefalse3truetruefalse0.27660.2766falsefalsefalsetruefalse4truetruefalse0.10210.1021falsefalsefalsetruefalse5truetruefalse0.04450.0445falsefalsefalsetruefalse6truetruefalse0.15510.1551falsefalsefalsetruefalse7truetruefalse0.05230.0523falsefalsefalsetruefalse8truetruefalse-0.3721-0.3721falsefalsefalsetruefalse9truetruefalse0.26080.2608falsefalsefalsetruefalse10truetruefalse0.14640.1464falsefalsefalsetruefalseOthernanafalsefalseInvestor A, B, C, Institutional BLACKROCK INDEX EQUITY PORTFOLIO Investor A Shares101Annual Total Returns - [Bar Chart] UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to BarChartData.No authoritative reference available.falsefalseBar Chart [Table]27false0rr_BarChartClosingTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">During the ten-year period shown in the bar chart, the highest return for a quarter was 15.93% (quarter ended June 30, 2009) and the lowest return for a quarter was -22.02% (quarter ended December 31, 2008). The year-to-date return as of March 31, 2011 was 5.84%.</font></p> <p align="left"><font size="2" class="_mt" style="font-family: Arial;"> </font>&nbsp;</p> <p align="left">&nbsp;</p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseBar Chart Closing [Text Block]28false0rr_PerformanceTableHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00As of 12/31/10 Average Annual Total ReturnsfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThis item represents Average Anuual Total Returns. If a Multiple Class Fund offers a Class in the prospectus that converts into another Class after a stated period, compute average annual total returns in the table by using the returns of the other Class for the period after conversion.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit c -Subsection b falsefalsePerformance Table Heading29false0rr_PerformanceTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleAverageAnnualTotalReturnsTransposedBlackrockIndexEquityPortfolio row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvestorBCInstitutionalMember column dei_LegalEntityAxis compact cik000844779_S000001513Member column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact 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available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.14940.1494falsefalsefalsetruefalse2truetruetrue0.11200.1120falsefalsefalsetruefalse3truetruetrue0.10550.1055falsefalsefalsetruefalse4truetruetrue0.07250.0725falsefalsefalsetruefalse5truetruetrue0.09200.0920falsefalsefalsetruefalse6truetruetrue0.12750.1275falsefalsefalsetruefalse7truetruetrue0.15060.1506falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalse1 Yearduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_AverageAnnualReturnYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.02220.0222falsefalsefalsetruefalse2truetruetrue0.01360.0136falsefalsefalsetruefalse3truetruetrue0.00720.0072falsefalsefalsetruefalse4truetruetrue0.00780.0078falsefalsefalsetruefalse5truetruetrue0.00770.0077falsefalsefalsetruefalse6truetruetrue0.01160.0116falsefalsefalsetruefalse7truetruetrue0.02290.0229falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalse5 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_AverageAnnualReturnYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.01290.0129falsefalsefalsetruefalse2truetruetrue0.00600.0060falsefalsefalsetruefalse3truetruetrue0.00090.0009falsefalsefalsetruefalse4truetruetrue0.00200.0020falsefalsefalsetruefalse5truetruetrue0.00280.0028falsefalsefalsetruefalse6truetruetrue0.00120.0012falsefalsefalsetruefalse7truetruetrue0.01410.0141falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalse10 Yearsduration2011-04-29T00:00:002011-04-29T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004080Memberrr_ProspectusShareClassAxisexplicitMembertruefalseBefore Taxesrr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor A SharesBefore TaxesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.11200.1120falsefalsefalsetruefalse2truetruetrue0.01360.0136falsefalsefalsetruefalse3truetruetrue0.00600.0060falsefalsefalsetruefalseOthernanafalsefalseInvestor A Shares2falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004080Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseReturn After Taxes on Distributionsrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldirr_AfterTaxesOnDistributionsMemberrr_PerformanceMeasureAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor A SharesReturn After Taxes on DistributionsStandard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.10550.1055falsefalsefalsetruefalse2truetruetrue0.00720.0072falsefalsefalsetruefalse3truetruetrue0.00090.0009falsefalsefalsetruefalseOthernanafalsefalseInvestor A Shares Return After Taxes on Distributions3falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A 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Shares4falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor B Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004081Memberrr_ProspectusShareClassAxisexplicitMembertruefalseBefore Taxesrr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOInvestor B SharesBefore 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Shares7falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor A, B, C, Institutionaldei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvestorBCInstitutionalMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBLACKROCK INDEX EQUITY PORTFOLIOdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001513Memberdei_LegalEntityAxisexplicitMembertruefalseShare Classesrr_ProspectusShareClassAxisrr_ShareClassDomainrr_ProspectusShareClassAxisexplicitMemberfalsefalseS&P 500 Index (Reflects no deduction for fees, expenses or taxes)rr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_SP500IndexReflectsNoDeductionForFeesExpensesOrTaxesMemberrr_PerformanceMeasureAxisexplicitMemberInvestor A, B, C, InstitutionalBLACKROCK INDEX EQUITY PORTFOLIOShare ClassesS&P 500 Index (Reflects no deduction for fees, expenses or taxes)Standard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.15060.1506falsefalsefalsetruefalse2truetruetrue0.02290.0229falsefalsefalsetruefalse3truetruetrue0.01410.0141falsefalsefalsetruefalseOthernanafalsefalseS&P 500 Index (Reflects no deduction for fees, expenses or taxes)37Average Annual Total Returns - Investor A, B, C, Institutional BLACKROCK INDEX EQUITY PORTFOLIOUnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvestorBCInstitutionalMemberRowdei_LegalEntityAxisAxiscik000844779_S000001513MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to PerformanceTableData.No authoritative reference available.falsefalsePerformance [Table]30false0rr_PerformanceTableNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <p align="left"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt"><font class="_mt"><font style="font-family: Arial, Helvetica; font-size: 10pt;" class="_mt">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</font></font>. <font class="_mt">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</font>. <font class="_mt">After-tax returns are shown for Investor A Shares only, and the after-tax returns for Investor B, Investor C and Institutional Shares will vary</font>.</font></p></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a table showing the Fund's (A) average annual total return; (B) average annual total return (after taxes on distributions); and (C) average annual total return (after taxes on distributions and redemption). A Money Market Fund should show only the returns described in clause (A) of the preceding sentence. All returns should be shown for 1-, 5-, and 10- calendar year periods ending on the date of the most recently completed calendar year (or for the life of the Fund, if shorter), but only for periods subsequent to the effective date of the Fund's registration statement. The table also shouldshow the returns of an appropriate broadbased securities market index as defined in Instruction 5 to Item 22(b)(7) for the same periods. A Fund that has been in existence for more than 10 years also may include returns for the life of the Fund. A Money Market Fund may provide the Fund's 7-day yield ending on the date of the most recent calendar year or disclose a toll-free (or collect) telephone number that investors can use to obtain the Fund's current 7-day yield. For a Fund (other than a Money Market Fund or a Fund described in General Instruction C.3.(d)(iii)), provide the information in the following table with the specified captions AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, _____). For a Fund that provides annual total returns for only one calendar year or for a Fund that does not include the bar chart because it does not have annual returns for a full calendar year, modify, as appropriate, the narrative explanation required by paragraph (c)(2)(i) (e.g., by stating that the information gives some indication of the risks of an investment in the Fund by comparing the Fund's performance with a broad measure of market performance).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iv -Subsection b falsefalsePerformance Table Narrative129Risk/Return Summary - BLACKROCK INDEX EQUITY PORTFOLIO (Investor A, B, C, Institutional, BLACKROCK INDEX EQUITY PORTFOLIO)UnKnownUnKnownUnKnownUnKnownfalsetrue