Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Relating To Included In Other Investments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Liquidation Period Lower Range [Member] years	Dec. 31, 2011 Liquidation Period Upper Range [Member] years	Dec. 31, 2011 Fair Value [Member]	Dec. 31, 2010 Fair Value [Member]	Dec. 31, 2011 Maximum Future Funding Commitments [Member]	Dec. 31, 2010 Maximum Future Funding Commitments [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial			$ 205	$ 192	$ 141	$ 151
Real estate			270	163	96	92
Distressed			182	243	57	43
Mezzanine			195	125	282	173
Traditional			565	376	200	291
Vintage			18	27	1	3
Investment funds			378	329
Alternative investments total			$ 1,813	$ 1,455	$ 777	$ 753
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