Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Related To Investments) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Expected Liquidation Period Lower Range [Member] Y	Mar. 31, 2012 Expected Liquidation Period Upper Range [Member] Y	Mar. 31, 2012 Fair Value [Member]	Dec. 31, 2011 Fair Value [Member]	Mar. 31, 2012 Maximum Future Funding Commitments [Member]	Dec. 31, 2011 Maximum Future Funding Commitments [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial			$ 207	$ 205	$ 135	$ 141
Real estate			282	270	147	96
Distressed			189	182	52	57
Mezzanine			227	195	337	282
Traditional			579	565	525	200
Vintage			18	18	1	1
Investment funds			383	378
Alternative investments total			$ 1,885	$ 1,813	$ 1,197	$ 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