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	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
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	$ 51	$ 23	$ 53	$ 28
Additions where no OTTI was previously recorded	4	8	16	15
Additions where an OTTI was previously recorded	1	6	13	8
Reductions for securities sold during the period	(11)	(5)	(37)	(19)
Balance of credit losses related to securities still held – end of period	$ 45	$ 32	$ 45	$ 32