Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Available for sale, Due in 1 year or less, Amortized Cost	$ 3,569	$ 3,164
Available for sale, Due after 1 year through 5 years, Amortized Cost	27,134	24,749
Available for sale, Due after 5 years though 10 years, Amortized Cost	24,095	25,388
Available for sale, Due after 10 years, Amortized Cost	8,767	9,255
Available for sale, Mortgage-backed securities, Amortized Cost	15,758	15,279
Debt Securities, Available-for-sale, Amortized Cost	79,323	77,835
Available for sale, Due in 1 year or less, Fair Value	3,568	3,182
Available for sale, Due after 1 year through 5 years, Fair Value	27,005	25,068
Available for sale, Due after 5 years through 10 years, Fair Value	23,543	25,704
Available for sale, Due after 10 years, Fair Value	8,814	9,695
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	63,565	62,556
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	62,930	63,649
Available for sale, Mortgage backed securities, Fair Value	15,540	15,290
Available for sale, Fair Value	78,470	78,939
Held to maturity, Due in 1 year or less, Amortized Cost	536	743
Held to maturity, Due after 1 year through 5 years, Amortized Cost	3,122	2,669
Held to maturity, Due after 5 years through 10 years, Amortized Cost	4,468	4,744
Held to maturity, Due after 10 years, Amortized Cost	2,785	3,455
Held to maturity, Mortgage backed securities, Amortized Cost	2,524	2,724
Debt Securities, Held-to-maturity	13,435	14,335
Held to maturity, Due in 1 year or less, Fair Value	537	746
Held to maturity, Due after 1 year through 5, Fair Value	3,106	2,688
Held to maturity, Due after 5 years through 10 years, Fair Value	4,407	4,756
Held to maturity, Due after 10 years, Fair Value	2,723	3,542
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	10,911	11,611
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	10,773	11,732
Held to maturity, Mortgage backed securities, Fair Value	2,486	2,742
Held to maturity, Fair Value	$ 13,259	$ 14,474