Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Principal Investments [Member]
Fair Values of Direct and Indirect Funds and Direct and Indirect Unfunded Commitments for Funds [Abstract]
Fair Value	$ 485
Unfunded Commitments	115
Principal Investments [Member] | Hedge funds [Member]
Fair Values of Direct and Indirect Funds and Direct and Indirect Unfunded Commitments for Funds [Abstract]
Fair Value	5
Principal Investments [Member] | Private equity funds [Member]
Fair Values of Direct and Indirect Funds and Direct and Indirect Unfunded Commitments for Funds [Abstract]
Fair Value	480
Unfunded Commitments	115
Private Equity and Mezzanine Investments [Member]
Fair Values of Direct and Indirect Funds and Direct and Indirect Unfunded Commitments for Funds [Abstract]
Fair Value	42
Unfunded Commitments	7
Private Equity and Mezzanine Investments [Member] | Passive Funds [Member]
Fair Values of Direct and Indirect Funds and Direct and Indirect Unfunded Commitments for Funds [Abstract]
Fair Value	17
Unfunded Commitments	4
Private Equity and Mezzanine Investments [Member] | Co Managed Funds [Member]
Fair Values of Direct and Indirect Funds and Direct and Indirect Unfunded Commitments for Funds [Abstract]
Fair Value	25
Unfunded Commitments	$ 3