Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Related To Investments) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial	$ 266	$ 256
Real estate	304	322
Distressed	289	180
Mezzanine	300	276
Traditional	960	813
Vintage	10	13
Investment funds	384	428
Total of alternative investments	2,513	2,288
Maximum Future Funding Commitments [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial	127	129
Real estate	43	92
Distressed	132	230
Mezzanine	213	252
Traditional	388	456
Vintage	0	0
Total of alternative investments	$ 903	$ 1,159
Expected Liquidation Period Lower Range [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Liquidation period for financial alternative investments (in years)	5 years	5 years
Liquidation period for real estate alternative investments (in years)	3 years	3 years
Liquidation period for distressed alternative investments (in years)	6 years	6 years
Liquidation period for mezzanine alternative investments (in years)	6 years	6 years
Liquidation period for traditional alternative investments (in years)	3 years	3 years
Liquidation period for vintage alternative investments (in years)	1 year	1 year
Expected Liquidation Period Upper Range [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Liquidation period for financial alternative investments (in years)	9 years	9 years
Liquidation period for real estate alternative investments (in years)	9 years	9 years
Liquidation period for distressed alternative investments (in years)	9 years	9 years
Liquidation period for mezzanine alternative investments (in years)	9 years	9 years
Liquidation period for traditional alternative investments (in years)	8 years	8 years
Liquidation period for vintage alternative investments (in years)	3 years	3 years