Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available for sale, Due in 1 year or less, Amortized Cost	$ 3,951	$ 3,569
Available for sale, Due after 1 year through 5 years, Amortized Cost	27,142	27,134
Available for sale, Due after 5 years though 10 years, Amortized Cost	23,901	24,095
Available for sale, Due after 10 years, Amortized Cost	8,874	8,767
Available for sale, Mortgage-backed securities, Amortized Cost	18,712	15,758
Debt Securities, Available-for-sale, Amortized Cost	82,580	79,323
Available for sale, Due in 1 year or less, Fair Value	3,973	3,568
Available for sale, Due after 1 year through 5 years, Fair Value	27,720	27,005
Available for sale, Due after 5 years through 10 years, Fair Value	24,874	23,543
Available for sale, Due after 10 years, Fair Value	9,729	8,814
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	63,868	63,565
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	66,296	62,930
Available for sale, Mortgage backed securities, Fair Value	19,192	15,540
Available for sale, Fair Value	85,488	78,470
Held to maturity, Due in 1 year or less, Amortized Cost	478	536
Held to maturity, Due after 1 year through 5 years, Amortized Cost	3,869	3,122
Held to maturity, Due after 5 years through 10 years, Amortized Cost	3,756	4,468
Held to maturity, Due after 10 years, Amortized Cost	2,147	2,785
Held to maturity, Mortgage backed securities, Amortized Cost	2,331	2,524
Debt Securities, Held-to-maturity	12,581	13,435
Held to maturity, Due in 1 year or less, Fair Value	479	537
Held to maturity, Due after 1 year through 5, Fair Value	3,940	3,106
Held to maturity, Due after 5 years through 10 years, Fair Value	3,883	4,407
Held to maturity, Due after 10 years, Fair Value	2,307	2,723
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	10,250	10,911
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	10,609	10,773
Held to maturity, Mortgage backed securities, Fair Value	2,396	2,486
Held to maturity, Fair Value	$ 13,005	$ 13,259