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		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Investment [Line Items]
Balance of credit losses related to securities still held-beginning of period	$ 47	$ 94	$ 74	$ 137
Additions where no OTTI was previously recorded	1	6	3	8
Additions where an OTTI was previously recorded	6	3	11	4
Reductions for securities sold during the period	(4)	(24)	(38)	(70)
Balance of credit losses related to securities still held-end of period	$ 50	$ 79	$ 50	$ 79