Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Available for sale, Due in 1 year or less, Fair Value	$ 4,767	$ 4,760
Available for sale, Due after 1 year through 5 years, Fair Value	26,100	26,227
Available for sale, Due after 5 years through 10 years, Fair Value	27,394	27,232
Available for sale, Due after 10 years, Fair Value	13,373	14,010
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	71,634	72,229
Available for sale, Mortgage backed securities, Fair Value	19,437	18,470
Available for sale, Fair Value	91,071	90,699
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, within one year, net carrying value	1,099	1,231
Held to maturity, Due in 1 year or less, Fair Value	1,109	1,240
Held-to-maturity, after one through five years, net carrying value	3,471	3,592
Held to maturity, Due after 1 year through 5, Fair Value	3,613	3,760
Held-to-maturity, after 5 through 10 years, net carrying value	2,918	3,029
Held to maturity, Due after 5 years through 10 years, Fair Value	3,072	3,228
Held-to-maturity, after 10 years, net carrying value	1,757	1,802
Held to maturity, Due after 10 years, Fair Value	1,961	2,136
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, net carrying value	9,245	9,654
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	9,755	10,364
Held-to-maturity, MBS, net carrying value	1,887	1,999
Held to maturity, Mortgage backed securities, Fair Value	1,997	2,146
Debt securities, held to maturity, net carrying value	11,132	11,653
Held to maturity, Fair Value	$ 11,752	$ 12,510