Fair Value Measurements (Fair Value And Maximum Future Funding Commitments Related To Investments) (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Minimum [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 assets alternative investments (in years)	3 years	3 years
Liquidation period for distressed alternative investments (in years)	5 years	5 years
Liquidation period for private credit alternative investments (in years)	3 years	3 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
Maximum [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 assets alternative investments (in years)	7 years	7 years
Liquidation period for distressed alternative investments (in years)	9 years	9 years
Liquidation period for private credit alternative investments (in years)	7 years	7 years
Liquidation period for traditional alternative investments (in years)	9 years	9 years
Liquidation period for vintage alternative investments (in years)	2 years	2 years
Fair Value [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial	$ 306	$ 282
Real assets	460	451
Distressed	242	232
Private credit	291	299
Traditional	897	908
Vintage	16	11
Investment funds	306	378
Total of alternative investments	2,518	2,561
Maximum Future Funding Commitments [Member]
Fair Value And Maximum Future Funding Commitments Related To Investments [Line Items]
Financial	124	145
Real assets	177	210
Distressed	252	175
Private credit	234	190
Traditional	224	289
Vintage	0	1
Investment funds	0	0
Total of alternative investments	$ 1,011	$ 1,010