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	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Roll-Forward Of Pre-Tax Credit Losses Related To Fixed Maturities For Which Portion Of OTTI Was Recognized In OCI
Balance of credit losses related to securities still held-beginning of period	$ 74	$ 137	$ 174
Additions where no OTTI was previously recorded	8	12	34
Additions where an OTTI was previously recorded	12	8	12
Reductions for securities sold during the period	(51)	(83)	(83)
Balance of credit losses related to securities still held-end of period	$ 43	$ 74	$ 137