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Investments (Schedule Of Amortized Cost and Fair Value of Available-for-Sale Securities) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 119,441		$ 111,128
Debt Securities, Available-for-sale, Allowance for Credit Loss	(75)	$ (122)	(156)	$ (158)	$ (193)	$ (169)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,008		1,148
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(4,109)		(5,549)
Available for sale, Fair Value	117,265		106,571
U.S. Treasury / Agency
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,709		3,721
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	18		13
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(98)		(144)
Available for sale, Fair Value	2,629		3,590
Non-U.S.
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	37,560		35,918
Debt Securities, Available-for-sale, Allowance for Credit Loss	(23)		(49)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	895		592
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(931)		(1,297)
Available for sale, Fair Value	37,501		35,164
Corporate and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	47,588		44,695
Debt Securities, Available-for-sale, Allowance for Credit Loss	(52)		(104)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	736		390
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,579)		(2,151)
Available for sale, Fair Value	46,693		42,830
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	29,517		23,720
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		(3)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	341		143
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,384)		(1,802)
Available for sale, Fair Value	28,474		22,058
Municipal
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,067		3,074
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	18		10
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(117)		(155)
Available for sale, Fair Value	$ 1,968		$ 2,929