Investments (Schedule Of Amortized Cost And Fair Value Of Held-to-Maturity And Related Other-Than-Temporary Impairment Recognized In Accumulated Other Comprehensive Income) (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 10,153	$ 11,697
Debt Securities, Held-to-maturity, Allowance for Credit Loss	35	44	$ 0
Debt securities, held to maturity, net carrying value	10,118	11,653
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	533	859
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(4)	(2)
Held to maturity, Fair Value	10,647	12,510
U.S. Treasury and agency
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,213	1,392
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0	0
Debt securities, held to maturity, net carrying value	1,213	1,392
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	34	60
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(3)	0
Held to maturity, Fair Value	1,244	1,452
Foreign
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,201	1,295
Debt Securities, Held-to-maturity, Allowance for Credit Loss	5	7
Debt securities, held to maturity, net carrying value	1,196	1,288
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	66	118
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	(1)
Held to maturity, Fair Value	1,262	1,405
Corporate securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	2,032	2,185
Debt Securities, Held-to-maturity, Allowance for Credit Loss	28	35
Debt securities, held to maturity, net carrying value	2,004	2,150
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	197	288
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held to maturity, Fair Value	2,201	2,438
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,731	2,000
Debt Securities, Held-to-maturity, Allowance for Credit Loss	1	1
Debt securities, held to maturity, net carrying value	1,730	1,999
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	74	148
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(1)	(1)
Held to maturity, Fair Value	1,803	2,146
States, municipalities, and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	3,976	4,825
Debt Securities, Held-to-maturity, Allowance for Credit Loss	1	1
Debt securities, held to maturity, net carrying value	3,975	4,824
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	162	245
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held to maturity, Fair Value	$ 4,137	$ 5,069