Investments (Schedule Of Fixed Maturities By Contractual Maturity) (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available for sale, Due in 1 year or less, Amortized Cost	$ 3,613	$ 3,569
Available for sale, Due after 1 year through 5 years, Amortized Cost	26,776	27,134
Available for sale, Due after 5 years though 10 years, Amortized Cost	22,957	24,095
Available for sale, Due after 10 years, Amortized Cost	9,176	8,767
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost	62,522	63,565
Available for sale, Mortgage-backed securities, Amortized Cost	17,597	15,758
Available for sale, at amortized cost	80,119	79,323
Available for sale, Due in 1 year or less, Fair Value	3,630	3,568
Available for sale, Due after 1 year through 5 years, Fair Value	27,281	27,005
Available for sale, Due after 5 years through 10 years, Fair Value	23,711	23,543
Available for sale, Due after 10 years, Fair Value	9,822	8,814
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	64,444	62,930
Available for sale, Mortgage backed securities, Fair Value	17,966	15,540
Available for sale, Fair Value	82,410	78,470
Held to maturity, Due in 1 year or less, Amortized Cost	545	536
Held to maturity, Due after 1 year through 5 years, Amortized Cost	3,267	3,122
Held to maturity, Due after 5 years through 10 years, Amortized Cost	4,082	4,468
Held to maturity, Due after 10 years, Amortized Cost	2,502	2,785
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	10,396	10,911
Held to maturity, Mortgage backed securities, Amortized Cost	2,442	2,524
Held to maturity, Amortized Cost	12,838	13,435
Held to maturity, Due in 1 year or less, Fair Value	548	537
Held to maturity, Due after 1 year through 5, Fair Value	3,315	3,106
Held to maturity, Due after 5 years through 10 years, Fair Value	4,192	4,407
Held to maturity, Due after 10 years, Fair Value	2,620	2,723
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	10,675	10,773
Held to maturity, Mortgage backed securities, Fair Value	2,502	2,486
Held to maturity, Fair Value	$ 13,177	$ 13,259