Fair Value Disclosures (Investments in Certain Entities Calculate Net Asset Value Per Share) (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012 Consolidated Sponsored Investment Funds, Private Equity Funds Of Funds [Member]	Dec. 31, 2011 Consolidated Sponsored Investment Funds, Private Equity Funds Of Funds [Member]	Sep. 30, 2012 Equity Method, Hedge Funds / Funds Of Hedge Funds [Member]	Dec. 31, 2011 Equity Method, Hedge Funds / Funds Of Hedge Funds [Member]	Sep. 30, 2012 Equity Method, Private Equity Funds [Member]	Dec. 30, 2011 Equity Method, Private Equity Funds [Member]	Sep. 30, 2012 Equity Method, Real Estate Funds [Member]	Dec. 31, 2011 Equity Method, Real Estate Funds [Member]	Sep. 30, 2012 Consolidated Variable Interest Entity Assets Private Equity Fund [Member]	Dec. 31, 2011 Consolidated Variable Interest Entity Assets Private Equity Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Liquidation period, years	7 years	8 years	5 years	6 years	5 years	6 years	7 years	7 years	3 years	4 years
Total remaining unfunded commitments to other third parties, private equity funds	$ 34	$ 44							$ 2	$ 2
Amount of unfunded commitments contractually obligated to fund	$ 30	$ 33