Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Dec. 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
Debt Securities, Available-for-sale, Amortized Cost	$ 85,188	82,580
Available for sale, Due in 1 year or less, Fair Value	4,760	3,973
Available for sale, Due after 1 year through 5 years, Fair Value	26,227	27,720
Available for sale, Due after 5 years through 10 years, Fair Value	27,232	24,874
Available for sale, Due after 10 years, Fair Value	14,010	9,729
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	72,229	66,296
Available for sale, Mortgage backed securities, Fair Value	18,470	19,192
Available for sale, Fair Value	90,699	85,488
Held to maturity, Due in 1 year or less, Amortized Cost		478
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, within on year, net carrying value	1,231
Held to maturity, Due after 1 year through 5 years, Amortized Cost		3,869
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, after one through five years, net carrying value	3,592
Held to maturity, Due after 5 years through 10 years, Amortized Cost		3,756
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, after five through ten years, net carrying value	3,029
Held to maturity, Due after 10 years, Amortized Cost		2,147
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, after 10 years, net carrying value	1,802
Debt securities, Held-to-maturity, maturity, allocated and single maturity date, net carrying value	9,654
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
Debt securities, Held-to-maturity, without single maturity date, net carrying value	1,999
Debt Securities, Held-to-maturity	11,697	12,581
Held to maturity, Due in 1 year or less, Fair Value	1,240	479
Held to maturity, Due after 1 year through 5, Fair Value	3,760	3,940
Held to maturity, Due after 5 years through 10 years, Fair Value	3,228	3,883
Held to maturity, Due after 10 years, Fair Value	2,136	2,307
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	10,364	10,609
Held to maturity, Mortgage backed securities, Fair Value	2,146	2,396
Debt securities, held to maturity, net carrying value	11,653
Held to maturity, Fair Value	$ 12,510	$ 13,005