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Investments (Schedule Of Amortized Cost and Fair Value of Available-for-Sale Securities) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 123,726		$ 115,083
Debt Securities, Available-for-sale, Allowance for Credit Loss	(50)	$ (71)	(70)	$ (75)	$ (122)	$ (156)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,042		1,119
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(3,930)		(5,769)
Available for sale, Fair Value	121,788		110,363
U.S. and local government securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,046		4,383
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	24		10
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(224)		(323)
Available for sale, Fair Value	3,846		4,070
Non-U.S.
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	40,176		36,311
Debt Securities, Available-for-sale, Allowance for Credit Loss	(15)		(23)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	986		753
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(816)		(1,203)
Available for sale, Fair Value	40,331		35,838
Corporate and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	48,360		45,231
Debt Securities, Available-for-sale, Allowance for Credit Loss	(35)		(47)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	706		287
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,580)		(2,264)
Available for sale, Fair Value	47,451		43,207
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	31,144		29,158
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	326		69
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,310)		(1,979)
Available for sale, Fair Value	$ 30,160		$ 27,248