Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available for sale, Due in 1 year or less, Amortized Cost	$ 3,869	$ 3,569
Available for sale, Due after 1 year through 5 years, Amortized Cost	27,168	27,134
Available for sale, Due after 5 years though 10 years, Amortized Cost	23,368	24,095
Available for sale, Due after 10 years, Amortized Cost	9,174	8,767
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	63,579	63,565
Available for sale, Mortgage-backed securities, Amortized Cost	18,457	15,758
Available for sale, at amortized cost	82,036	79,323
Available for sale, Due in 1 year or less, Fair Value	3,889	3,568
Available for sale, Due after 1 year through 5 years, Fair Value	27,728	27,005
Available for sale, Due after 5 years through 10 years, Fair Value	24,309	23,543
Available for sale, Due after 10 years, Fair Value	10,104	8,814
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	66,030	62,930
Available for sale, Mortgage backed securities, Fair Value	19,014	15,540
Available for sale, Fair Value	85,044	78,470
Held to maturity, Due in 1 year or less, Amortized Cost	487	536
Held to maturity, Due after 1 year through 5 years, Amortized Cost	3,567	3,122
Held to maturity, Due after 5 years through 10 years, Amortized Cost	3,822	4,468
Held to maturity, Due after 10 years, Amortized Cost	2,355	2,785
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	10,231	10,911
Held to maturity, Mortgage backed securities, Amortized Cost	2,391	2,524
Held to maturity, Amortized Cost	12,622	13,435
Held to maturity, Due in 1 year or less, Fair Value	490	537
Held to maturity, Due after 1 year through 5, Fair Value	3,629	3,106
Held to maturity, Due after 5 years through 10 years, Fair Value	3,959	4,407
Held to maturity, Due after 10 years, Fair Value	2,544	2,723
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	10,622	10,773
Held to maturity, Mortgage backed securities, Fair Value	2,474	2,486
Held to maturity, Fair Value	$ 13,096	$ 13,259