Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Related To Investments) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair Value
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial	282	256
Real estate	289	322
Distressed	281	180
Mezzanine	301	276
Traditional	1,021	813
Vintage	9	13
Investment funds	378	428
Total of alternative investments	2,561	2,288
Maximum Future Funding Commitments
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial	145	129
Real estate	40	92
Distressed	225	230
Mezzanine	191	252
Traditional	409	456
Total of alternative investments	1,010	1,159
Expected Liquidation Period Lower Range
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Liquidation period for financial alternative investments	5 years	5 years
Liquidation period for real estate alternative investments	3 years	3 years
Liquidation period for distressed alternative investments	5 years	5 years
Liquidation period for mezzanine alternative investments	3 years	3 years
Liquidation period for traditional alternative investments	3 years	3 years
Liquidation period for vintage alternative investments	1 year	1 year
Expected Liquidation Period Upper Range
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Liquidation period for financial alternative investments	9 years	9 years
Liquidation period for real estate alternative investments	7 years	7 years
Liquidation period for distressed alternative investments	9 years	9 years
Liquidation period for mezzanine alternative investments	7 years	7 years
Liquidation period for traditional alternative investments	9 years	9 years
Liquidation period for vintage alternative investments	2 years	2 years