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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
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	$ 30	$ 16	$ 34	$ 22
Additions where no OTTI was previously recorded	17	6	28	7
Additions where an OTTI was previously recorded	1	2	4	2
Reductions for securities sold during the period	(8)	(3)	(26)	(10)
Balance of credit losses related to securities still held – end of period	$ 40	$ 21	$ 40	$ 21