Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Related To Investments) (Detail) (USD $) In Millions, unless otherwise specified					6 Months Ended
	Jun. 30, 2012 Fair Value [Member]	Dec. 31, 2011 Fair Value [Member]	Jun. 30, 2012 Maximum Future Funding Commitments [Member]	Dec. 31, 2011 Maximum Future Funding Commitments [Member]	Jun. 30, 2012 Expected Liquidation Period Lower Range [Member] Year	Jun. 30, 2012 Expected Liquidation Period Upper Range [Member] Year
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial	$ 206	$ 205	$ 127	$ 141
Real estate	289	270	95	96
Distressed	188	182	149	57
Mezzanine	271	195	297	282
Traditional	621	565	515	200
Vintage	17	18	1	1
Investment funds	383	378
Total of alternative investments	$ 1,975	$ 1,813	$ 1,184	$ 777
Liquidation period for financial alternative investments (in years)					5	9
Liquidation period for real estate alternative investments (in years)					3	9
Liquidation period for distressed alternative investments (in years)					6	9
Liquidation period for mezzanine alternative investments (in years)					6	9
Liquidation period for traditional alternative investments (in years)					3	8
Liquidation period for vintage alternative investments (in years)					1	3