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, 2019	Dec. 31, 2018
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	$ 34	$ 22
Additions where no OTTI was previously recorded	33	20
Additions where an OTTI was previously recorded	4	5
Reductions for securities sold during the period	(41)	(13)
Balance of credit losses related to securities still held-end of period	$ 30	$ 34