2.2.0.25truefalse007001 - Document - Risk/Return Summary {Unlabeled} (Small Cap Core Equity Portfolio) (INV INST)falsefalsetrue1falsefalseUSDtruefalse{dei_DocumentInformationDocumentAxis} : Inv Inst Member {dei_LegalEntityAxis} : S000001508 Member 1/28/2011 - 1/28/2011 USD ($) $Duration_1_28_2011_To_1_28_20117http://www.sec.gov/CIK0000844779duration2011-01-28T00:00:002011-01-28T00:00:00falsefalsecik000844779_InvInstMemberdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalsecik000844779_S000001508Memberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit1Standardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$1false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.blackrock.com/role/documentriskreturnsummaryunlabeledsmallcapcoreequityportfolioinvinst1falsefalsefalse00INV INST | BlackRock Small Cap Core Equity PortfolioINV INST | BlackRock Small Cap Core Equity Portfoliofalsefalsefalsefalsefalse1falsefalseUSDtruefalse{dei_DocumentInformationDocumentAxis} : Inv Inst Member {dei_LegalEntityAxis} : S000001508 Member 1/28/2011 - 1/28/2011 USD ($) $Duration_1_28_2011_To_1_28_20117http://www.sec.gov/CIK0000844779duration2011-01-28T00:00:002011-01-28T00:00:00falsefalsecik000844779_InvInstMemberdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalsecik000844779_S000001508Memberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170Unit1Standardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseINV INST | BlackRock Small Cap Core Equity Portfolio3false0rr_RiskReturnHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <div><font class="_mt" size="5">Fund Overview</font> </div> <div class="MetaData">&nbsp;</div> <div><b>Key Facts About BlackRock Small Cap Core Equity Portfolio</b></div></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 style="text-align: left;"><b><i>Investment Objective</i></b> </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>The investment objective of BlackRock Small Cap Core Equity Portfolio ("Small Cap Core Equity" or the "Fund"), a series of BlackRock Funds^SM(the "Trust"), is long-term capital appreciation.</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 style="text-align: left;"><b><i>Fees and Expenses of the Fund</i></b></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 style="text-align: left; margin-top: 0px; margin-bottom: 0px;">This table describes the fees and expenses that you may pay if you buy and hold shares of Small Cap Core Equity.&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 $<font class="_mt">25,000</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 39 of the Fund's prospectus and in the "Purchase of Shares" section on page II-57 of the Fund's statement of additional information.</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. Modify the narrative explanation to state that Fund shares are sold on a national securities exchange at the end of the time periods indicated, and that brokerage commissions for buying and selling Fund shares through a broker are not reflected.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph b -Subsection instructions falsefalseExpense Narrative [Text Block]8false0rr_ShareholderFeesCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p style="text-align: left; margin-top: 0px; margin-bottom: 0px;"><strong>Shareholder Fees</strong></p> <p style="text-align: left; margin-top: 0px; margin-bottom: 0px;"><strong>(fees paid directly from your investment)</strong></p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringShareholder Fees (fees paid directly from your investment).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subsection table falsefalseShareholder Fees Caption [Text]9false0rr_ShareholderFeesTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleShareholderFeesSmallCapCoreEquityPortfolioInvInst column period compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvInstMember column dei_LegalEntityAxis compact cik000844779_S000001508Member column rr_ProspectusShareClassAxis compact * row primary compact * ~&lt;/div&gt; 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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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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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"Redemption Fee" includes a fee charged for any redemption of the Fund's shares, but does not include a deferred sales charge (load) imposed upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph b -Subsection instructions falsefalseRedemption Fee (as a percentage of amount redeemed or exchanged within 30 days)0rr_RedemptionFeeOverRedemptiontruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.020.02falsefalsefalsetruefalse2truetruetrue0.020.02falsefalsefalsetruefalse3truetruetrue0.020.02falsefalsefalsetruefalse4truetruetrue0.020.02falsefalsefalsetruefalseOthernanafalsefalseRedemption Fee (as a percentage of amount redeemed or exchanged within 30 days)1 A contingent deferred sales charge ("CDSC") of 1.00% is assessed on certain redemptions of Investor A Shares made within 18 months after purchase where no initial sales charge was paid at time of purchase as part of an investment of $1,000,000 or more. 2 The CDSC is 4.50% if shares are redeemed in less than one year. The CDSC for Investor B Shares decreases for redemptions made in subsequent years. After six years there is no CDSC on Investor B Shares. 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SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*5false0rr_ManagementFeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.010.01falsefalsefalsetruefalse2truetruetrue0.010.01falsefalsefalsetruefalse3truetruetrue0.010.01falsefalsefalsetruefalse4truetruetrue0.010.01falsefalsefalsetruefalseOtherrr: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_ManagementFeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.010.01falsefalsefalsetruefalse2truetruetrue0.010.01falsefalsefalsetruefalse3truetruetrue0.010.01falsefalsefalsetruefalse4truetruetrue0.010.01falsefalsefalsetruefalseOthernanafalsefalseManagement Fee2falseRowprimaryElement*6false0rr_DistributionAndService12b1FeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00250.0025falsefalsefalsetruefalse2truetruetrue0.010.01falsefalsefalsetruefalse3truetruetrue0.010.01falsefalsefalsetruefalse4truetruetrue00falsefalsefalsetruefalseOtherrr: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_DistributionAndService12b1FeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00250.0025falsefalsefalsetruefalse2truetruetrue0.010.01falsefalsefalsetruefalse3truetruetrue0.010.01falsefalsefalsetruefalse4truetruetrue00falsefalsefalsetruefalseOthernanafalsefalseDistribution and/or Service (12b-1) Fees3falseRowprimaryElement*7false0rr_OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00730.0073falsefalsefalsetruefalse2truetruetrue0.00670.0067falsefalsefalsetruefalse3truetruetrue0.00630.0063falsefalsefalsetruefalse4truetruetrue0.0040.004falsefalsefalsetruefalseOtherrr: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 falsefalseOther Expenses0rr_OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00730.0073falsefalsefalsetruefalse2truetruetrue0.00670.0067falsefalsefalsetruefalse3truetruetrue0.00630.0063falsefalsefalsetruefalse4truetruetrue0.0040.004falsefalsefalsetruefalseOthernanafalsefalseOther Expenses4falseRowprimaryElement*8false0rr_AcquiredFundFeesAndExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00010.0001[2]falsefalsefalsetruefalse2truetruetrue0.00010.0001[2]falsefalsefalsetruefalse3truetruetrue0.00010.0001[2]falsefalsefalsetruefalse4truetruetrue0.00010.0001[2]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 falsefalseAcquired Fund Fees and Expenses0rr_AcquiredFundFeesAndExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[1]1truetruetrue0.00010.0001falsefalsefalsetruefalse2truetruetrue0.00010.0001falsefalsefalsetruefalse3truetruetrue0.00010.0001falsefalsefalsetruefalse4truetruetrue0.00010.0001falsefalsefalsetruefalseOthernanafalsefalseAcquired Fund Fees and Expenses5falseRowprimaryElement*9false0rr_ExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truetruetrue0.01990.0199[2]falsefalsefalsetruefalse2truetruetrue0.02680.0268[2]falsefalsefalsetruefalse3truetruetrue0.02640.0264[2]falsefalsefalsetruefalse4truetruetrue0.01410.0141[2]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[1]1truetruetrue0.01990.0199falsefalsefalsetruefalse2truetruetrue0.02680.0268falsefalsefalsetruefalse3truetruetrue0.02640.0264falsefalsefalsetruefalse4truetruetrue0.01410.0141falsefalsefalsetruefalseOthernanafalsefalseTotal Annual Fund Operating Expenses6falseRowprimaryElement*10false0rr_FeeWaiverOrReimbursementOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue-0.0016-0.0016[1]falsefalsefalsetruefalse2truetruetrue-0.0007-0.0007[1]falsefalsefalsetruefalse3truetruetrue-0.0003-0.0003[1]falsefalsefalsetruefalse4truetruetrue-0.0006-0.0006[1]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[2]1truetruetrue-0.0016-0.0016falsefalsefalsetruefalse2truetruetrue-0.0007-0.0007falsefalsefalsetruefalse3truetruetrue-0.0003-0.0003falsefalsefalsetruefalse4truetruetrue-0.0006-0.0006falsefalsefalsetruefalseOthernanafalsefalseFee Waivers and/or Expense Reimbursements7falseRowprimaryElement*11false0rr_NetExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truetruetrue0.01830.0183[1]falsefalsefalsetruefalse2truetruetrue0.02610.0261[1]falsefalsefalsetruefalse3truetruetrue0.02610.0261[1]falsefalsefalsetruefalse4truetruetrue0.01350.0135[1]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[2]1truetruetrue0.01830.0183falsefalsefalsetruefalse2truetruetrue0.02610.0261falsefalsefalsetruefalse3truetruetrue0.02610.0261falsefalsefalsetruefalse4truetruetrue0.01350.0135falsefalsefalsetruefalseOthernanafalsefalseTotal Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements1The Total Annual Fund Operating Expenses do not correlate to the ratio 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.2As described in the "Management of the Funds" section of the Fund's prospectus on pages 55-62, 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 1.82% (for Investor A Shares), 2.60% (for Investor B and Investor C Shares) and 1.34% (for Institutional Shares) until February 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 a vote of a majority of the outstanding voting securities of the Fund. 47Annual Fund Operating Expenses (Small Cap Core Equity Portfolio) (INV INST) INV INST BlackRock Small Cap Core Equity PortfolioUnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberColumndei_LegalEntityAxisAxiscik000844779_S000001508MemberColumnrr_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 style="text-align: left;"><b>Example:</b></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 style="text-align: left;">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:</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/ScheduleExpenseExampleTransposedSmallCapCoreEquityPortfolioInvInst row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvInstMember column dei_LegalEntityAxis compact cik000844779_S000001508Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleExpenseExampleTransposedSmallCapCoreEquityPortfolioInvInst row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvInstMember column dei_LegalEntityAxis compact cik000844779_S000001508Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>truehttp://www.blackrock.com/role/ScheduleExpenseExampleTransposedSmallCapCoreEquityPortfolioInvInstfalsefalse007004 - Schedule - Expense Example {Transposed} (Small Cap Core Equity Portfolio) (INV INST)truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*5false0rr_ExpenseExampleYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue701701falsefalsefalsetruefalse2truefalsetrue714714falsefalsefalsetruefalse3truefalsetrue364364falsefalsefalsetruefalse4truefalsetrue137137falsefalsefalsetruefalseMonetaryrr: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 Yearduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_ExpenseExampleYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue11021102falsefalsefalsetruefalse2truefalsetrue11761176falsefalsefalsetruefalse3truefalsetrue818818falsefalsefalsetruefalse4truefalsetrue440440falsefalsefalsetruefalseMonetaryrr: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 Yearsduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_ExpenseExampleYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue15271527falsefalsefalsetruefalse2truefalsetrue16141614falsefalsefalsetruefalse3truefalsetrue13971397falsefalsefalsetruefalse4truefalsetrue765765falsefalsefalsetruefalseMonetaryrr: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 Yearsduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*8false0rr_ExpenseExampleYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue27082708falsefalsefalsetruefalse2truefalsetrue28412841falsefalsefalsetruefalse3truefalsetrue29712971falsefalsefalsetruefalse4truefalsetrue16861686falsefalsefalsetruefalseMonetaryrr: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 Yearsduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004054Memberrr_ProspectusShareClassAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor A SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue701701falsefalsefalsetruefalse2truefalsetrue11021102falsefalsefalsetruefalse3truefalsetrue15271527falsefalsefalsetruefalse4truefalsetrue27082708falsefalsefalsetruefalseOthernanafalsefalseInvestor A Shares2falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor B Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004055Memberrr_ProspectusShareClassAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor B SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue714714falsefalsefalsetruefalse2truefalsetrue11761176falsefalsefalsetruefalse3truefalsetrue16141614falsefalsefalsetruefalse4truefalsetrue28412841falsefalsefalsetruefalseOthernanafalsefalseInvestor B Shares3falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor C Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004056Memberrr_ProspectusShareClassAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor C SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue364364falsefalsefalsetruefalse2truefalsetrue818818falsefalsefalsetruefalse3truefalsetrue13971397falsefalsefalsetruefalse4truefalsetrue29712971falsefalsefalsetruefalseOthernanafalsefalseInvestor C Shares4falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInstitutional Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004052Memberrr_ProspectusShareClassAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInstitutional SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue137137falsefalsefalsetruefalse2truefalsetrue440440falsefalsefalsetruefalse3truefalsetrue765765falsefalsefalsetruefalse4truefalsetrue16861686falsefalsefalsetruefalseOthernanafalsefalseInstitutional Shares44Expense Example (Small Cap Core Equity Portfolio) (INV INST) INV INST BlackRock Small Cap Core Equity Portfolio (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_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_ExpenseExampleNoRedemptionByYearCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <p style="text-align: left;">You would pay the following expenses if you did not redeem your shares:</p></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringYou 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 falsefalseExpense Example, No Redemption, By Year, Caption [Text]16false0rr_ExpenseExampleNoRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleExpenseExampleNoRedemptionTransposedSmallCapCoreEquityPortfolioInvInst row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvInstMember column dei_LegalEntityAxis compact cik000844779_S000001508Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsefalse<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleExpenseExampleNoRedemptionTransposedSmallCapCoreEquityPortfolioInvInst row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000844779_InvInstMember column dei_LegalEntityAxis compact cik000844779_S000001508Member column rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>truehttp://www.blackrock.com/role/ScheduleExpenseExampleNoRedemptionTransposedSmallCapCoreEquityPortfolioInvInstfalsefalse007005 - Schedule - Expense Example, No Redemption {Transposed} (Small Cap Core Equity Portfolio) (INV INST)truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*5false0rr_ExpenseExampleNoRedemptionYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue264264falsefalsefalsetruefalse2truefalsetrue264264falsefalsefalsetruefalseMonetaryrr: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 Yearduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_ExpenseExampleNoRedemptionYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue826826falsefalsefalsetruefalse2truefalsetrue818818falsefalsefalsetruefalseMonetaryrr: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 Yearsduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_ExpenseExampleNoRedemptionYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue14141414falsefalsefalsetruefalse2truefalsetrue13971397falsefalsefalsetruefalseMonetaryrr: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 Yearsduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*8false0rr_ExpenseExampleNoRedemptionYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue28412841falsefalsefalsetruefalse2truefalsetrue29712971falsefalsefalsetruefalseMonetaryrr: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 Yearsduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor B Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004055Memberrr_ProspectusShareClassAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor B SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue264264falsefalsefalsetruefalse2truefalsetrue826826falsefalsefalsetruefalse3truefalsetrue14141414falsefalsefalsetruefalse4truefalsetrue28412841falsefalsefalsetruefalseOthernanafalsefalseInvestor B Shares2falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor C Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004056Memberrr_ProspectusShareClassAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor C SharesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue264264falsefalsefalsetruefalse2truefalsetrue818818falsefalsefalsetruefalse3truefalsetrue13971397falsefalsefalsetruefalse4truefalsetrue29712971falsefalsefalsetruefalseOthernanafalsefalseInvestor C Shares42Expense Example, No Redemption (Small Cap Core Equity Portfolio) (INV INST) INV INST BlackRock Small Cap Core Equity Portfolio (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_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 style="text-align: left;"><b>Portfolio Turnover:</b></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 style="text-align: left;">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&nbsp;<font class="_mt">119%</font> of the average value of its portfolio.</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 style="text-align: left;"><b><i>Principal Investment Strategies of the Fund</i></b></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 style="text-align: left;"><font class="_mt">Small Cap Core Equity normally invests at least 80% of its net assets in the equity securities of U.S. small capitalization companies which Fund management believes either have above-average earnings growth potential or are undervalued. </font>Equity securities consist primarily of common stock, preferred stock, securities convertible into common stock and securities or other instruments whose price is linked to the value of common stock. Although a universal definition of small capitalization companies does not exist, the Fund generally defines these companies, at the time of the Fund's investment, as those with market capitalizations comparable in size to the companies in the Russell 2000^&#174; Index (between approximately $39 million and $2.536 billion as of June 30, 2010, the most recent rebalance date). The Fund primarily buys common stock but can also invest in preferred stock and convertible securities. From time to time the Fund may invest in shares of companies through "new issues" or initial public offerings ("IPOs"). The Fund may invest in real estate investment trusts ("REITs"), which own interests in real estate or in real estate related loans or other interests, and have revenue primarily consisting of rent derived from owned, income producing real estate properties and capital gains from the sale of such properties.</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<b><i>Principal Risks of Investing in the Fund</i></b>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 style="text-align: left;">Risk is inherent in all investing. The value of your investment in Small Cap Core Equity, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time.&nbsp;<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.</p> <ul> <li> <p><b><i>Convertible Securities Risk </i></b>&#8212; The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer's credit rating or the market's perception of the issuer's creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risk as apply to the underlying common stock.</p></li> <li> <p><b><i>Equity Securities Risk </i></b>&#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. </p></li> <li> <p><b><i>Investment Style Risk </i></b>&#8212; Under certain market conditions, growth investments have performed better during the later stages of economic expansion and value investments have performed better during periods of economic recovery. Therefore, these investment styles may over time go in and out of favor. At times when the investment style used by the Fund is out of favor, the Fund may underperform other equity funds that use different investment styles.</p></li> <li> <p><b><i>Market Risk and Selection Risk </i></b>&#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.</p></li> <li> <p><b><i>"New Issues" Risk </i></b>&#8212; "New Issues" are initial public offerings of U.S. equity securities. Securities issued in IPOs have no trading history, and information about the companies may be available for very limited periods. In addition, the prices of securities sold in IPOs may be highly volatile or may decline shortly after the initial public offering.</p></li> <li> <p><b><i>REIT Investment Risk </i></b>&#8212; Investments in REITs involve unique risks. REITs may have limited financial resources, may trade less frequently and in limited volume and may be more volatile than other securities.</p></li> <li> <p><b><i>Small Cap Securities Risk </i></b>&#8212; Small cap 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.</p></li></ul></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 style="text-align: left;"><b><i>Performance Information</i></b></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 style="text-align: left;"><font class="_mt">The information shows you how Small Cap Core Equity's performance has varied year by year and provides some indication of the risks of investing in the Fund. </font>The table compares the Fund's performance to that of the Russell 2000^&#174; Index.&nbsp;<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. If they were, returns would be less than those shown.&nbsp;</font><font class="_mt">However, the table includes all applicable fees and sales charges.</font> 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 results can be obtained by visiting&nbsp;<font class="_mt">http://www.blackrock.com/funds</font> or can be obtained by phone at <font class="_mt">800-882-0052.</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 style="text-align: center;"><b>Investor A Shares</b><br /><b>ANNUAL TOTAL RETURNS</b><br /><b>BlackRock Small Cap Core Equity Portfolio</b><br /><b>As of 12/31</b></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/ScheduleAnnualTotalReturnsBarChartSmallCapCoreEquityPortfolioInvInst column period compact * column primary compact * row dei_DocumentInformationDocumentAxis compact cik000844779_InvInstMember row dei_LegalEntityAxis compact cik000844779_S000001508Member row rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsefalseBarChart1.jpg<div> &lt;div style="display:none;" &gt;~ http://www.blackrock.com/role/ScheduleAnnualTotalReturnsBarChartSmallCapCoreEquityPortfolioInvInst column period compact * column primary compact * row dei_DocumentInformationDocumentAxis compact cik000844779_InvInstMember row dei_LegalEntityAxis compact cik000844779_S000001508Member row rr_ProspectusShareClassAxis compact * ~&lt;/div&gt; </div>falsehttp://www.blackrock.com/role/ScheduleAnnualTotalReturnsBarChartSmallCapCoreEquityPortfolioInvInstfalsefalse007006 - Schedule - Annual Total Returns (Small Cap Core Equity Portfolio) (INV INST)truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*5false0rr_AnnualReturn2002rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.11-0.11falsefalsefalsetruefalseOtherxbrli: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 2002duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*6false0rr_AnnualReturn2003rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.57180.5718falsefalsefalsetruefalseOtherxbrli: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 2003duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*7false0rr_AnnualReturn2004rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.20970.2097falsefalsefalsetruefalseOtherxbrli: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 2004duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*8false0rr_AnnualReturn2005rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.0670.067falsefalsefalsetruefalseOtherxbrli: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 2005duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$5falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*9false0rr_AnnualReturn2006rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.12840.1284falsefalsefalsetruefalseOtherxbrli: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 2006duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$6falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*10false0rr_AnnualReturn2007rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.03750.0375falsefalsefalsetruefalseOtherxbrli: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 2007duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$7falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*11false0rr_AnnualReturn2008rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.3597-0.3597falsefalsefalsetruefalseOtherxbrli: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 2008duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$8falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*12false0rr_AnnualReturn2009rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.18870.1887falsefalsefalsetruefalseOtherxbrli: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 2009duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$9falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*13false0rr_AnnualReturn2010rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.2050.205falsefalsefalsetruefalseOtherxbrli: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 2010duration2011-01-28T00:00:002011-01-28T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004054Memberrr_ProspectusShareClassAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor A Shares0truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.11-0.11falsefalsefalsetruefalse2truetruefalse0.57180.5718falsefalsefalsetruefalse3truetruefalse0.20970.2097falsefalsefalsetruefalse4truetruefalse0.0670.067falsefalsefalsetruefalse5truetruefalse0.12840.1284falsefalsefalsetruefalse6truetruefalse0.03750.0375falsefalsefalsetruefalse7truetruefalse-0.3597-0.3597falsefalsefalsetruefalse8truetruefalse0.18870.1887falsefalsefalsetruefalse9truetruefalse0.2050.205falsefalsefalsetruefalseOthernanafalsefalseINV INST BlackRock Small Cap Core Equity Portfolio Investor A Shares91Annual Total Returns (Small Cap Core Equity Portfolio) (INV INST) UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_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 style="text-align: left;">During the period shown in the bar chart, the&nbsp;<font class="_mt">highest return</font> for a quarter was&nbsp;<font class="_mt">25.44%</font> (quarter ended June 30, 2003) and the&nbsp;<font class="_mt">lowest return</font> for a quarter was&nbsp;<font class="_mt">-24.09%</font> (quarter ended December 31, 2008).</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.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <div style="font-family: 'Arial'; font-size: 10pt;"><strong>As of 12/31/10</strong></div> <div style="font-family: 'Arial'; font-size: 10pt;"><strong>Average Annual Total Returns</strong></div></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThis item represents Average Anuual Total Returns. 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available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.14160.1416falsefalsefalsetruefalse2truetruetrue0.14160.1416falsefalsefalsetruefalse3truetruetrue0.09210.0921falsefalsefalsetruefalse4truetruetrue0.15070.1507falsefalsefalsetruefalse5truetruetrue0.18530.1853falsefalsefalsetruefalse6truetruetrue0.21040.2104falsefalsefalsetruefalse7truetruetrue0.26850.2685falsefalsefalsetruefalseOtherxbrli: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 Yearduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_AverageAnnualReturnYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00340.0034falsefalsefalsetruefalse2truetruetrue-0.0005-0.0005falsefalsefalsetruefalse3truetruetrue0.00210.0021falsefalsefalsetruefalse4truetruetrue0.00280.0028falsefalsefalsetruefalse5truetruetrue0.00670.0067falsefalsefalsetruefalse6truetruetrue0.01890.0189falsefalsefalsetruefalse7truetruetrue0.04470.0447falsefalsefalsetruefalseOtherxbrli: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 Yearsduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_AverageAnnualReturnSinceInceptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.070.07falsefalsefalsetruefalse2truetruetrue0.06680.0668falsefalsefalsetruefalse3truetruetrue0.06070.0607falsefalsefalsetruefalse4truetruetrue0.07080.0708falsefalsefalsetruefalse5truetruetrue0.070.07falsefalsefalsetruefalse6truetruetrue0.08020.0802falsefalsefalsetruefalse7truetruetrue0.06790.0679falsefalsefalsetruefalseOtherxbrli: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 falsefalseSince Inceptionduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*8false0rr_AverageAnnualReturnInceptionDaterrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse002002-01-02falsefalsetruetruefalse2falsetruefalse002002-01-02falsefalsetruetruefalse3falsetruefalse002002-01-02falsefalsetruetruefalse4falsetruefalse002002-01-02falsefalsetruetruefalse5falsetruefalse002002-01-02falsefalsetruetruefalse6falsetruefalse002002-01-02falsefalsetruetruefalse7falsetruefalse00falsefalsetruetruefalseOtherxbrli:dateItemTypedateReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 4 -Subsection b falsefalseInception Dateduration2011-01-28T00:00:002011-01-28T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004054Memberrr_ProspectusShareClassAxisexplicitMembertruefalseBefore Taxesrr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor A SharesBefore TaxesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.14160.1416falsefalsefalsetruefalse2truetruetrue0.00340.0034falsefalsefalsetruefalse3truetruetrue0.070.07falsefalsefalsetruefalse4falsetruefalse002002-01-022002-01-02falsefalsetruetruefalseOthernanafalsefalseInvestor A Shares2falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMemberfalsefalseInvestor A Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004054Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseReturn After Taxes on Distributionsrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldirr_AfterTaxesOnDistributionsMemberrr_PerformanceMeasureAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInvestor A SharesReturn After Taxes on DistributionsStandard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.14160.1416falsefalsefalsetruefalse2truetruetrue-0.0005-0.0005falsefalsefalsetruefalse3truetruetrue0.06680.0668falsefalsefalsetruefalse4falsetruefalse002002-01-022002-01-02falsefalsetruetruefalseOthernanafalsefalseInvestor A Shares Return After Taxes on Distributions3falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseINV 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Sharesrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_C000004052Memberrr_ProspectusShareClassAxisexplicitMembertruefalseBefore Taxesrr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioInstitutional SharesBefore TaxesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.21040.2104falsefalsefalsetruefalse2truetruetrue0.01890.0189falsefalsefalsetruefalse3truetruetrue0.08020.0802falsefalsefalsetruefalse4falsetruefalse002002-01-022002-01-02falsefalsetruetruefalseOthernanafalsefalseInstitutional Shares7falseRowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseINV INSTdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_InvInstMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseBlackRock Small Cap Core Equity Portfoliodei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_S000001508Memberdei_LegalEntityAxisexplicitMembertruefalseShare Classesrr_ProspectusShareClassAxisrr_ShareClassDomainrr_ProspectusShareClassAxisexplicitMemberfalsefalseRussell 2000 Index (Reflects no deduction for fees, expenses or taxes)rr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldicik000844779_Russell2000IndexMemberrr_PerformanceMeasureAxisexplicitMemberINV INSTBlackRock Small Cap Core Equity PortfolioShare ClassesRussell 2000 Index (Reflects no deduction for fees, expenses or taxes)Standard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.26850.2685falsefalsefalsetruefalse2truetruetrue0.04470.0447falsefalsefalsetruefalse3truetruetrue0.06790.0679falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsefalsefalseOthernanafalsefalseRussell 2000 Index (Reflects no deduction for fees, expenses or taxes)47Average Annual Total Returns (Small Cap Core Equity Portfolio) (INV INST) INV INST BlackRock Small Cap Core Equity PortfolioUnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000844779_InvInstMemberRowdei_LegalEntityAxisAxiscik000844779_S000001508MemberRowrr_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 style="text-align: left;"><font 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.&nbsp;</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></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 (Small Cap Core Equity Portfolio) (INV INST) (INV INST, BlackRock Small Cap Core Equity Portfolio)UnKnownUnKnownUnKnownUnKnownfalsetrue