Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Available for sale, Due in 1 year or less, Amortized Cost		$ 3,951
Available for sale, Due after 1 year through 5 years, Amortized Cost		27,142
Available for sale, Due after 5 years though 10 years, Amortized Cost		23,901
Available for sale, Due after 10 years, Amortized Cost		8,874
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost		63,868
Available for sale, Mortgage-backed securities, Amortized Cost		18,712
Available for sale, at amortized cost	$ 80,959	82,580
Available for sale, Due in 1 year or less, Fair Value	3,816	3,973
Available for sale, Due after 1 year through 5 years, Fair Value	25,837	27,720
Available for sale, Due after 5 years through 10 years, Fair Value	23,712	24,874
Available for sale, Due after 10 years, Fair Value	10,280	9,729
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	63,645	66,296
Available for sale, Mortgage backed securities, Fair Value	17,885	19,192
Available for sale, Fair Value	81,530	85,488
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, within one year, net carrying value	614
Held to maturity, Due in 1 year or less, Amortized Cost		478
Held to maturity, Due after 1 year through 5 years, Amortized Cost		3,869
Held to maturity, Due after 5 years through 10 years, Amortized Cost		3,756
Held to maturity, Due after 10 years, Amortized Cost		2,147
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost		10,250
Held to maturity, Mortgage backed securities, Amortized Cost		2,331
Held to maturity, Amortized Cost	12,070	12,581
Held to maturity, Due in 1 year or less, Fair Value	620	479
Held-to-maturity, after one through five years, net carrying value	3,695
Held to maturity, Due after 1 year through 5, Fair Value	3,775	3,940
Held-to-maturity, after 5 through 10 years, net carrying value	3,383
Held to maturity, Due after 5 years through 10 years, Fair Value	3,479	3,883
Held-to-maturity, after 10 years, net carrying value	2,068
Held to maturity, Due after 10 years, Fair Value	2,230	2,307
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, net carrying value	9,760
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	10,104	10,609
Held-to-maturity, MBS, net carrying value	2,265
Held to maturity, Mortgage backed securities, Fair Value	2,367	2,396
Debt securities, held to maturity, net carrying value	12,025
Held to maturity, Fair Value	$ 12,471	$ 13,005