Fair Value Measurements (Details) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011
Fair Value Measurements (Textuals) [Abstract]
Notice Period to redeem quarterly investments (in days)	45 days
Principal Investments [Member]
Fair values of the direct and indirect funds and the direct and indirect unfunded commitments for funds [Abstract]
Fair Value	$ 470
Unfunded Commitments	143
Principal Investments [Member] | Private Equity Funds [Member]
Fair values of the direct and indirect funds and the direct and indirect unfunded commitments for funds [Abstract]
Fair Value	463
Unfunded Commitments	143
Principal Investments [Member] | Hedge Funds [Member]
Fair values of the direct and indirect funds and the direct and indirect unfunded commitments for funds [Abstract]
Fair Value	7
Private Equity And Mezzanine Investments [Member]
Fair values of the direct and indirect funds and the direct and indirect unfunded commitments for funds [Abstract]
Fair Value	33
Unfunded Commitments	14
Private Equity And Mezzanine Investments [Member] | Passive funds [Member]
Fair values of the direct and indirect funds and the direct and indirect unfunded commitments for funds [Abstract]
Fair Value	16
Unfunded Commitments	5
Private Equity And Mezzanine Investments [Member] | Co managed funds [Member]
Fair values of the direct and indirect funds and the direct and indirect unfunded commitments for funds [Abstract]
Fair Value	17
Unfunded Commitments	$ 9
Private Equity Funds [Member]
Fair Value Estimate Not Practicable (Textuals)
Liquidation period of funds, minimum (in years)	1 year
Liquidation period of funds, maximum (in years)	10 years
Passive funds [Member]
Fair Value Estimate Not Practicable (Textuals)
Liquidation period of funds, minimum (in years)	1 year
Liquidation period of funds, maximum (in years)	7 years
Co managed funds [Member]
Fair Value Estimate Not Practicable (Textuals)
Maturity Period of funds, minimum (in Years)	3 years
Maturity Period of funds, maximum (in Years)	6 years