Investments (Roll-Forward Of Pre-Tax Credit Losses Related To Fixed Maturities For Which Portion Of Other-Than-Temporary Impairment Was Recognized In Other Comprehensive Income) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Investment [Line Items]
Balance of credit losses related to securities still held-beginning of period	$ 55	$ 96	$ 74	$ 137
Additions where no OTTI was previously recorded	1	2	2	2
Additions where an OTTI was previously recorded			5	1
Reductions for securities sold during the period	(9)	(4)	(34)	(46)
Balance of credit losses related to securities still held-end of period	$ 47	$ 94	$ 47	$ 94