v2.4.0.8

Fair Value Option - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | Sep. 30, 2014 | Dec. 31, 2013
--- | --- | ---
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |  |
Fair value of financial instruments more than one day past due | $ 3,004 | [1] | $ 57,837 | [1]
Fair value of financial instruments with non-accrual status |  |  | 0 |
Loans And Receivables |  |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |  |
Fair value of financial instruments more than one day past due |  |  | 0 |
Fair value of financial instruments with non-accrual status |  |  | 0 |
Corporate Bonds |  |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |  |
Fair value of financial instruments more than one day past due | 0 |  | 0 |
Fair value of financial instruments with non-accrual status | $ 0 |  | $ 0 |
[1] | Corporate Loans and Corporate Bonds within CLO assets are classified as past due if contractual payments are more than one day past due.

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- Definition Fair Value of Financial Instruments More Than One Day Past Due + References No definition available. + Details
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Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Investment Securities Fair Value Disclosure On Nonaccrual Status + References No definition available. + Details
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Namespace Prefix: | bx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration