Accelerated Amortization Of Equity Based Compensation Awards [Member] Accelerated Amortization Of Equity Based Compensation Awards [Member] Accelerated Amortization Of Equity-Based Compensation Awards [Member] Accounts Payable And Accrued Liabilities Current And Noncurrent Accounts payable and accrued liabilities Accounts Payable And Accrued Liabilities Fair Value Disclosure Accounts payable and accrued liabilities Accounts Receivable Fair Value Disclosure Accounts receivable Accounts Receivable Net Accounts receivable Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Property and equipment, accumulated depreciation Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated other comprehensive loss Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income (Loss) [Member] Acquired Finite Lived Intangible Assets Amount Acquired Finite Lived Intangible Assets Amount Acquired finite-lived private equity management contracts Acquired Indefinite Lived Intangible Asset Amount Acquired indefinite-lived ETP management contracts Acquisition 1 [Member] Acquisition 1 [Member] Claymore Investments, Inc. [Member] Acquisition 2 [Member] Acquisition 2 [Member] Swiss Re Private Partners [Member] Acquisitions [Axis] Acquisitions [Axis] Acquisitions [Axis] Acquisitions [Domain] Acquisitions [Domain] Acquisitions [Domain] Additional Paid In Capital Additional paid-in capital Additional Paid In Capital Common Stock Additional Paid-in Capital, value of stock Additional Paid In Capital [Member] Additional Paid-In Capital [Member] Additional Paid In Capital Preferred Stock Additional Paid-in Capital, value of stock Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Stock-based compensation Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation Net tax benefit (shortfall) from stock-based compensation Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Adjustments to reconcile net income to cash flows from operating activities: ADVISORY FEE RECEIVABLES [MEMBER] Advisory Fee Receivables [Member] Advisory Fee Receivables [Member] Affiliated Entities [Member] Affiliated Entities [Member] Related Parties [Member] Affiliates And Non Affiliates [Axis] Affiliates And Non Affiliates [Axis] Affiliates And Non Affiliates [Axis] Affiliates And Non Affiliates [Domain] Affiliates And Non Affiliates [Domain] Affiliates And Non Affiliates [Domain] Allocation of losses of consolidated loan obligations Allocation Of Losses Of Consolidated Loan Obligations Allocation of losses of consolidated collateralized loan obligations Alternative Investment Products [Member] Alternative Investment Products [Member] Alternatives [Member] Alternative Investments Fair Value Disclosure Fair Value Amendment Flag Amendment Flag Amendments To Fair Value Measurements And Disclosures [Policy Text Block] Amendments To Fair Value Measurements And Disclosures Policy [Text Block] Amendments To Fair Value Measurements And Disclosures Americas [Member] Americas [Member] Americas [Member] Amortization Of Deferred Sales Commissions Amortization of deferred sales commissions Amortization Of Intangible Assets Amortization of intangible assets Amortization expense Contractually Obligated To Fund To The Consolidated Funds. Amount Of Unfunded Commitments Contractually Obligated To Fund Amount of unfunded commitments contractually obligated to fund Antidilutive securities excluded from earnings per share computation Antidilutive Securities Excluded From Earnings Per Share Computation Anti-dilutive securities excluded from earning per share computation Anti Dilutive Shares Excluded From Computation Of Diluted Net Earnings Loss Per Share Anti Dilutive Shares Excluded From Computation Of Diluted Net Earnings Loss Per Share Excluded from diluted EPS Appropriated Retained Earnings [Policy Text Block] Appropriated Retained Earnings Policy [Text Block] Appropriated Retained Earnings Asia-Pacific [Member] Asia Pacific [Member] Asia-Pacific [Member] Asset Backed Securities [Member] Asset-backed Securities [Member] Assets Total assets Assets [Abstract] Assets Assets Fair Value Disclosure Total assets measured at fair value on a recurring basis Assets Of Consolidated VIEs Bonds [Member] Assets Of Consolidated V I E Bonds [Member] Assets Of Consolidated VIEs Bonds [Member] Assets of Consolidated VIEs Bank Loans [Member] Assets Of Consolidated Vies Bank Loans [Member] Assets Of Consolidated VIEs Bank Loans [Member] Available For Sale Debt Securities Fair Value Disclosure Available For Sale Debt Securities Fair Value Disclosure Available-for-sale: Debt securities Available For Sale Equity And Fixed Income Securities Fair Value Disclosure Available For Sale Equity And Fixed Income Securities Fair Value Disclosure Available-for-sale: Equity securities (funds and CDOs) Available For Sale Securities Available-for-sale investments Carrying Value Available For Sale Securities Amortized Cost Cost Available For Sale Securities Fair Value Disclosure Total available-for-sale Availableforsale Securities Gross Unrealized Gain Gross Unrealized, Gains Available For Sale Securities Gross Unrealized Losses 1 Gross Unrealized, Losses Available For Sale Securities [Text Block] Summary Of The Cost And Carrying Value Of Investments Classified As Available-For-Sale Awards Vested, Not Converted Awards Vested Not Converted Awards vested, not converted Award Type [Axis] Award Type [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Changes in assets and liabilities of consolidated VIEs bank loans and investments Bank Loans And Investments Net (purchases) proceeds within consolidated VIEs Barclays Bank [Member] Barclays Bank [Member] Barclays Bank PLC ("Barclays") [Member] Barclays [Member] Barclays [Member] Barclays [Member] Basis Of Presentation And Significant Accounting Policies [Text Block] Basis Of Presentation Borrowings [Member] CLO Borrowings [Member] Capital Contribution Capital Contributed PNC preferred stock capital contribution Capital Required For Capital Adequacy Net capital requirement in certain regulated subsidiaries Carried Interest [Member] Carried Interest [Member] Carried Interest [Member] Carrying Reported Amount Fair Value Disclosure [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Cash And Cash Equivalents Cash And Cash Equivalents Change in cash and cash equivalents Cash And Cash Equivalents At Carrying Value Cash and cash equivalents, end of period Cash and cash equivalents, beginning of period Cash and cash equivalents Cash and cash equivalents of consolidated variable interest entity fair value disclosure. Cash And Cash Equivalents Of Consolidated Variable Interest Entity Fair Value Disclosure Cash and cash equivalents of consolidated VIEs Cash And Cash Equivalents Period Increase Decrease Net increase (decrease) in cash and cash equivalents Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Supplemental schedule of non-cash investing and financing transactions: Cash Management [Member] Cash Management [Member] Cash Management [Member] Assets and liabilities of consolidated VIEs Changes In Assets And Liabilities Of Consolidated Vies [Abstract] Assets and liabilities of consolidated VIEs: Classification Of Variable Interest Entity [Domain] Variable Interest Entity, Classification [Domain] Class Of Stock [Domain] Class of Stock [Domain] CLO Bank Loans [Member] Clo Bank Loans [Member] CLO Bank Loans [Member] Collateral Cash And Securities Received In Exchange Of Value Of Securities Lent In Order To Reduce Credit Risk Collateral Cash And Securities Received In Exchange Of Value Of Securities Lent In Order To Reduce Credit Risk Collateral cash and securities received in exchange of value of securities lent in order to reduce counterparty risk This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents equity securities in collateral held under securities lending agreements as of the balance sheet date. Collateral Held Under Securities Lending Agreements Equity Fair Value Disclosure Collateral held under securities lending agreements: Equity securities This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents securities in collateral held under securities lending agreements as of the balance sheet date. Collateral Held Under Securities Lending Agreements Fair Value Disclosure Total collateral held under securities lending agreements This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents fixed income securities in collateral held under securities lending agreements as of the balance sheet date. Collateral Held Under Securities Lending Agreements Fixed Income Fair Value Disclosure Collateral held under securities lending agreements: Debt securities Collateralized Debt Obligations [Member] Collateralized Debt Obligations [Member] Collateralized loan obligation Collateralized Loan Obligation Consolidation of a collateralized loan obligation Collateralized Loan Obligations [Member] Collateralized Loan Obligations [Member] Additional borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed. Commercial Paper Maximum Borrowing Capacity Additional Additional amount available, subject to lender credit approval Commercial Paper [Member] Commercial Paper [Member] Commitments And Contingencies Commitments and contingencies (Note 11) Commitments And Contingencies Disclosure [Text Block] Commitments and Contingencies Common Shares Held In Escrow [Member] Common Shares Held In Escrow [Member] Common Shares Held In Escrow [Member] Common shares issued related to employee stock transactions and convertible debt conversions Common Shares Issued Related To Employee Stock Transactions And Convertible Debt Conversions Convertible debt conversions Common Stock Dividends Per Share Cash Paid Cash dividends declared and paid per share Common Stock [Member] Common Stock [Member] Common Stock Par Or Stated Value Per Share Common stock, par value Common Stock Shares Authorized Common stock, Shares authorized Common Stock Shares Issued Common stock, Shares issued Common Stock Shares Outstanding Common stock, Shares outstanding Common Stock Underwriters Option To Purchase Exercised Common Stock Underwriters Option To Purchase Exercised Underwriters' option to purchase additional shares Common Stock Value Common stock, $0.01 par value; Shares authorized: 500,000,000 at September 30, 2012 and December 31, 2011; Shares issued: 168,661,718 and 139,880,380 at September 30, 2012 and December 31, 2011, respectively; Shares outstanding: 167,102,878 and 138,463,135 at September 30, 2012 and December 31, 2011, respectively Comprehensive Income Net Of Tax Comprehensive income attributable to BlackRock, Inc. Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest Comprehensive income Consolidated Equity Securities [Member] Consolidated Equity Securities [Member] Consolidated Equity Securities [Member] Consolidated sponsored investment funds classified as other investments. Consolidated Sponsored Investment Funds Classified As Other Investments Consolidated sponsored investment funds Information about consolidation of investment funds primarily because the Company is deemed to control such funds in accordance with GAAP. Consolidated Sponsored Investment Funds Disclosure [Text Block] Consolidated Sponsored Investment Funds Consolidated Sponsored Investment Funds, Hedge Funds / Funds of Funds [Member] Consolidated Sponsored Investment Funds Hedge Funds Funds Of Funds [Member] Consolidated Sponsored Investment Funds, Hedge Funds / Funds Of Funds [Member] Consolidated Sponsored Investment Funds Member. Consolidated Sponsored Investment Funds [Member] Consolidated Sponsored Investment Funds [Member] Consolidated Sponsored Investment Funds, Other Funds of Hedge Funds [Member] Consolidated Sponsored Investment Funds Other Funds Of Hedge Funds [Member] Consolidated Sponsored Investment Funds, Other Funds Of Hedge Funds [Member] This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents consolidated sponsored investments as of the balance sheet date. Consolidated Sponsored Investment Funds Total Fair Value Disclosure Total consolidated sponsored investment funds This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents consolidated sponsored investments held in hedge funds as of the balance sheet date. Consolidated Sponsored Investment Hedge Funds Fair Value Disclosure Consolidated sponsored investment funds: Hedge funds / Funds of funds This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents consolidated sponsored investments held in private equity funds as of the balance sheet date. Consolidated Sponsored Investment Private Equity Funds Fair Value Disclosure Consolidated sponsored investment funds: Private / public equity Private equity investments CONSOLIDATED SPONSORED INVESTMENT PRIVATE EQUITY FUNDS [MEMBER] Consolidated Sponsored Investment Private Equity Funds [Member] Consolidated Sponsored Investment Funds, Private Equity Funds Of Funds [Member] This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents consolidated sponsored investments held in real estate as of the balance sheet date. Consolidated Sponsored Investment Real Estate Fair Value Disclosure Consolidated Sponsored investment funds: Real estate This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This element represents the fair value of assets categorized as bonds of consolidated VIEs as of the balance sheet. Consolidated Variable Interest Entity Assets Bonds Fair Value Disclosure Assets of consolidated VIEs: Bonds Bonds CONSOLIDATED VARIABLE INTEREST ENTITY ASSETS PRIVATE EQUITY [MEMBER] Consolidated Variable Interest Entity Assets Private Equity [Member] Consolidated Variable Interest Entity Assets Private Equity Fund [Member] Conversion Of Class B Common Stock Into Class Common Stock Shares Conversion Of Class B Common Stock Into Class Common Stock Shares Inclusion of shares of common stock issued upon the conversion of Series B Convertible Participating Preferred Stock Conversion of series b convertible preferred shares to common stock. Conversion Of Series B Convertible Preferred Shares To Common Stock Preferred shares Conversion Of Stock Shares Converted 1 Common stock Conversion Price Per Share Per Share Amount Conversion Price Per Share Per Share Amount Repurchased shares price Convertible Preferred Stock [Member] Convertible Preferred Stock [Member] Corporate Debt Securities [Member] Corporate Debt [Member] Cost Method Investments Cost method investments(1) Cost Method Investments Fair Value Disclosure Cost method investments Costmethod Investments [Member] Total Cost Method Investments [Member] Credit Default Swap [Member] Credit Default Swap [Member] Credit default swap maximum risk of loss for credit protection related to Pillars synthetic CDO transaction Credit Default Swap Pillars Credit default swap maximum risk of loss for credit protection Credit Derivative Purchased Credit Protection Credit protection Credit Derivatives By Contract Type [Axis] Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type [Domain] Credit Derivatives Contract Type [Domain] Current Fiscal Year End Date Current Fiscal Year End Date Debt And Capital Lease Obligations Borrowings Borrowings of consolidated VIEs Borrowings Debt Disclosure [Text Block] Borrowings Debt Instrument Carrying Amount Maturity Amount Debt Instrument Face Amount Aggregate principal amount issued Debt Instrument Fair Value Fair Value Debt Instrument Interest Rate Stated Percentage Interest rate Debt Instrument Periodic Payment Interest Approximate annual interest expense Debt Instrument Unamortized Discount Unamortized discount Unamortized Discount Long-term debt issuance costs. Debt Issuance Costs Incurred Debt issuance costs incurred Debt [Line Items] Debt [Line Items] Debt [Line Items] Debt Securities Fair Value Disclosure Debt Securities Fair Value Disclosure Assets of consolidated VIEs: Debt securities Debt Securities [Member] Debt Securities [Member] Debt [Table] Debt [Table] Debt [Table] Deductions Charges [Abstract] Less: This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents certain deferred compensation plan hedge fund investments accounted for under the equity method of accounting as of the balance sheet date. Deferred Compensation Plan Hedge Fund Equity Method Investments Fair Value Disclosure Deferred compensation plan hedge fund equity method investments DEFERRED COMPENSATION PLAN HEDGE FUND EQUITY METHOD INVESTMENTS [MEMBER] Deferred Compensation Plan Hedge Fund Equity Method Investments [Member] Deferred Compensation Plan Hedge Fund Investments [Member] Deferred Compensation Plan Mutual Fund Investments. Deferred Compensation Plan Mutual Fund Investments [Member] Deferred Compensation Plan Mutual Fund Investments [Member] Deferred Income Tax Expense Benefit Deferred income tax expense (benefit) Deferred Income Tax Liabilities Deferred income tax liabilities Deferred sales commission asset are commissions paid to financial intermediaries upon the sale of certain funds sold without a front-end sales charge. Deferred Sales Commission Asset Deferred sales commissions, net Depreciation Amortization And Accretion Net Depreciation and amortization Derivative And Hedging [Table] Derivative And Hedging [Table] Derivative And Hedging [Table] Derivative Instruments And Hedging Activities Disclosure [Text Block] Derivatives and Hedging Derivative Instruments Not Designated As Hedging Instruments Asset At Fair Value Assets fair value Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net Amount of gains (losses) recognized in income on derivative instruments Derivative Instruments Not Designated As Hedging Instruments Liability At Fair Value Liabilities fair value Derivative [Line Items] Derivative [Line Items] Derivative Notional Amount Total return notional value of swaps Derivative Number Of Instruments Held Derivative, number of instruments held Derivatives Policy [Text Block] Derivative Instruments And Hedging Activities Derivative Swaption Interest Rate Interest on this swap, fixed rate Derivative [Table] Derivative [Table] Non-advisory expenses incurred by BlackRock related to certain funds for the use of certain index trademarks, reference data for certain indices, custodial services, fund administration, fund accounting, transfer agent services, shareholder reporting services, audit and tax services as well as other fund related expenses directly attributable to the non-advisory operations of the fund. Direct Fund Expenses Direct fund expenses Direct Investments [Member] Direct Investments [Member] Direct Investments [Member] Disclosure Borrowings Carrying Value And Fair Value Of Long Term Borrowings [Abstract] Disclosure Borrowings Carrying Value And Fair Value Of Long Term Borrowings [Abstract] Disclosure Borrowings Carrying Value And Fair Value Of Long Term Borrowings [Abstract] Disclosure Borrowings Narrative [Abstract] Disclosure Borrowings Narrative [Abstract] Disclosure Borrowings Narrative [Abstract] Disclosure - Business Overview (Narrative) [Abstract] Disclosure Business Overview Narrative [Abstract] Disclosure - Business Overview (Narrative) [Abstract] Disclosure Capital Stock Narrative [Abstract] Disclosure Capital Stock Narrative [Abstract] Disclosure Capital Stock Narrative [Abstract] Disclosure Capital Stock Preferred Shares Authorized Issued And Outstanding [Abstract] Disclosure Capital Stock Preferred Shares Authorized Issued And Outstanding [Abstract] Disclosure Capital Stock Preferred Shares Authorized Issued And Outstanding [Abstract] Disclosure Commitments And Contingencies [Abstract] Disclosure Commitments And Contingencies [Abstract] Disclosure Commitments And Contingencies [Abstract] Disclosure Consolidated Sponsored Investment Funds Consolidated Sponsored Investment Funds Included In Condensed Consolidated Statements Of Financial Condition [Abstract] Disclosure Consolidated Sponsored Investment Funds Consolidated Sponsored Investment Funds Included In Condensed Consolidated Statements Of Financial Condition [Abstract] Disclosure Consolidated Sponsored Investment Funds Consolidated Sponsored Investment Funds Included In Condensed Consolidated Statements Of Financial Condition [Abstract] Disclosure Consolidated Sponsored Investment Funds Narrative [Abstract] Disclosure Consolidated Sponsored Investment Funds Narrative [Abstract] Disclosure Consolidated Sponsored Investment Funds Narrative [Abstract] Disclosure Derivatives And Hedging Derivative Instruments Not Designated As Hedging Instruments [Abstract] Disclosure Derivatives And Hedging Derivative Instruments Not Designated As Hedging Instruments [Abstract] Disclosure Derivatives And Hedging Derivative Instruments Not Designated As Hedging Instruments [Abstract] Disclosure Derivatives And Hedging Narrative [Abstract] Disclosure Derivatives And Hedging Narrative [Abstract] Disclosure Derivatives And Hedging Narrative [Abstract] Disclosure Earnings Per Share Computation Of Basic And Diluted Earnings Per Share E P S [Abstract] Disclosure Earnings Per Share Computation Of Basic And Diluted Earnings Per Share E P S [Abstract] Disclosure Earnings Per Share Computation Of Basic And Diluted Earnings Per Share E P S [Abstract] Disclosure Earnings Per Share Narrative [Abstract] Disclosure Earnings Per Share Narrative [Abstract] Disclosure Earnings Per Share Narrative [Abstract] Disclosure Fair Value Disclosures Assets Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Assets Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Assets Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Changes In Level 3 Assets And Liabilities Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Changes In Level 3 Assets And Liabilities Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Changes In Level 3 Assets And Liabilities Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Fair Value Of Financial Assets And Financial Liabilities [Abstract] Disclosure Fair Value Disclosures Fair Value Of Financial Assets And Financial Liabilities [Abstract] Disclosure Fair Value Disclosures Fair Value Of Financial Assets And Financial Liabilities [Abstract] Disclosure Fair Value Disclosures Fair Value Of Selected Assets And Liabilities [Abstract] Disclosure Fair Value Disclosures Fair Value Of Selected Assets And Liabilities [Abstract] Disclosure Fair Value Disclosures Fair Value Of Selected Assets And Liabilities [Abstract] Disclosure Fair Value Disclosures Investments In Certain Entities Calculate Net Asset Value Per Share [Abstract] Disclosure Fair Value Disclosures Investments In Certain Entities Calculate Net Asset Value Per Share [Abstract] Disclosure Fair Value Disclosures Investments In Certain Entities Calculate Net Asset Value Per Share [Abstract] Disclosure Fair Value Disclosures Liabilities Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Liabilities Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Liabilities Measured At Fair Value On Recurring Basis [Abstract] Disclosure Fair Value Disclosures Narrative [Abstract] Disclosure Fair Value Disclosures Narrative [Abstract] Disclosure Fair Value Disclosures Narrative [Abstract] Disclosure Goodwill [Abstract] Disclosure Goodwill [Abstract] Disclosure Goodwill [Abstract] Disclosure Income Taxes Narrative [Abstract] Disclosure Income Taxes Narrative [Abstract] Disclosure Income Taxes Narrative [Abstract] Disclosure Intangible Assets Narrative [Abstract] Disclosure Intangible Assets Narrative [Abstract] Disclosure Intangible Assets Narrative [Abstract] Disclosure Intangible Assets Schedule Of The Carrying Amounts Of Identifiable Intangible Assets [Abstract] Disclosure Intangible Assets Schedule Of The Carrying Amounts Of Identifiable Intangible Assets [Abstract] Disclosure Intangible Assets Schedule Of The Carrying Amounts Of Identifiable Intangible Assets [Abstract] Disclosure Investments Narrative [Abstract] Disclosure Investments Narrative [Abstract] Disclosure Investments Narrative [Abstract] Disclosure - Investments (Schedule Of Amortized Cost Of Debt Securities Classified As Held-To-Maturity By Maturity Date) [Abstract] Disclosure Investments Schedule Of Amortized Cost Of Debt Securities Classified As Held To Maturity By Maturity Date [Abstract] Disclosure - Investments (Schedule Of Amortized Cost Of Debt Securities Classified As Held-To-Maturity By Maturity Date) [Abstract] Disclosure Investments Summary Of The Carrying Value Of Total Investments [Abstract] Disclosure Investments Summary Of The Carrying Value Of Total Investments [Abstract] Disclosure Investments Summary Of The Carrying Value Of Total Investments [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Investments Classified As Available For Sale [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Investments Classified As Available For Sale [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Investments Classified As Available For Sale [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Other Investments [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Other Investments [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Other Investments [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Trading Investments [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Trading Investments [Abstract] Disclosure Investments Summary Of The Cost And Carrying Value Of Trading Investments [Abstract] Disclosure Net Capital Requirements [Abstract] Disclosure Net Capital Requirements [Abstract] Disclosure Net Capital Requirements [Abstract] Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Stock-Based Compensation Disclosure Restructuring Charges Narrative [Abstract] Disclosure Restructuring Charges Narrative [Abstract] Disclosure Restructuring Charges Narrative [Abstract] Disclosure Restructuring Charges Rollforward Of Restructuring Liability [Abstract] Disclosure Restructuring Charges Rollforward Of Restructuring Liability [Abstract] Disclosure Restructuring Charges Rollforward Of Restructuring Liability [Abstract] Disclosure Segment Information Schedule Of Investment Advisory Administration Fees Securities Lending Revenue And Performance Fees Black Rock Solutions And Advisory Revenue Distribution Fees And Other Revenue [Abstract] Disclosure Segment Information Schedule Of Investment Advisory Administration Fees Securities Lending Revenue And Performance Fees Black Rock Solutions And Advisory Revenue Distribution Fees And Other Revenue [Abstract] Disclosure Segment Information Schedule Of Investment Advisory Administration Fees Securities Lending Revenue And Performance Fees Black Rock Solutions And Advisory Revenue Distribution Fees And Other Revenue [Abstract] Disclosure Segment Information Schedule Of Longlived Assets By Geographic Region [Abstract] Disclosure Segment Information Schedule Of Longlived Assets By Geographic Region [Abstract] Disclosure Segment Information Schedule Of Longlived Assets By Geographic Region [Abstract] Disclosure Segment Information Total Revenue By Geographic Region [Abstract] Disclosure Segment Information Total Revenue By Geographic Region [Abstract] Disclosure Segment Information Total Revenue By Geographic Region [Abstract] Disclosure Significant Accounting Policies Narrative [Abstract] Disclosure Significant Accounting Policies Narrative [Abstract] Disclosure Significant Accounting Policies Narrative [Abstract] Disclosure Stock Based Compensation Narrative [Abstract] Disclosure Stock Based Compensation Narrative [Abstract] Disclosure Stock Based Compensation Narrative [Abstract]