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
	Mar. 31, 2013	Mar. 31, 2012
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 [Roll Forward]
Balance of credit losses related to securities still held-beginning of period	$ 43	$ 74
Additions where no OTTI was previously recorded	0	1
Additions where an OTTI was previously recorded	1	5
Reductions for securities sold during the period	(9)	(25)
Balance of credit losses related to securities still held-end of period	$ 35	$ 55