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	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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	$ 22	$ 35	$ 53
Additions where no OTTI was previously recorded	20	4	17
Additions where an OTTI was previously recorded	5	2	14
Reductions for securities sold during the period	(13)	(19)	(49)
Balance of credit losses related to securities still held-end of period	$ 34	$ 22	$ 35