Investments (Schedule Of Amortized Cost and Fair Value of Available-for-Sale Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost	$ 111,128	$ 93,355
Debt Securities, Available-for-sale, Allowance for Credit Loss	(156)	(169)	$ (14)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,148	174
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(5,549)	(8,140)
Available for sale, Fair Value	106,571	85,220
U.S. Treasury / Agency
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost	3,721	2,792
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	13	5
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(144)	(171)
Available for sale, Fair Value	3,590	2,626
Non-U.S.
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost	35,918	28,064
Debt Securities, Available-for-sale, Allowance for Credit Loss	(49)	(59)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	592	108
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(1,297)	(2,205)
Available for sale, Fair Value	35,164	25,908
Corporate and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost	44,695	40,547
Debt Securities, Available-for-sale, Allowance for Credit Loss	(104)	(107)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	390	49
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(2,151)	(3,534)
Available for sale, Fair Value	42,830	36,955
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost	23,720	17,871
Debt Securities, Available-for-sale, Allowance for Credit Loss	(3)	(3)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	143	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(1,802)	(2,021)
Available for sale, Fair Value	22,058	15,851
Municipal
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Amortized Cost	3,074	4,081
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	10	8
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(155)	(209)
Available for sale, Fair Value	$ 2,929	$ 3,880

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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