Fair Value Disclosures (Assets Measured At Fair Value On Recurring Basis) (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments	$ 318	[1]	$ 331
Assets of consolidated VIEs: Private / public equity	1,445		1,207
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments	298	[1]	313
Significant Unobservable Inputs (Level 3) [Member] | Third Parties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments	240
Significant Unobservable Inputs (Level 3) [Member] | Direct Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments	58
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets of consolidated VIEs: Private / public equity	33	[2]	35
Variable Interest Entity, Primary Beneficiary [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets of consolidated VIEs: Private / public equity	26	[2]	27
Variable Interest Entity, Primary Beneficiary [Member] | Significant Unobservable Inputs (Level 3) [Member] | Third Parties [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets of consolidated VIEs: Private / public equity	24
Variable Interest Entity, Primary Beneficiary [Member] | Significant Unobservable Inputs (Level 3) [Member] | Direct Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets of consolidated VIEs: Private / public equity	$ 2

[1] Amount within Level 3 included $240 million and $58 million of underlying third-party private equity funds and direct investments in private equity companies held by private equity funds, respectively.

[2] Amount within Level 3 included $24 million and $2 million of underlying third-party private equity funds and direct investments in private equity companies held by private equity fund, respectively.