Investments (Schedule Of Amortized Cost and Fair Value of Available-for-Sale Securities) (Details) - USD ($) $ in Millions	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 118,947		$ 115,083
Debt Securities, Available-for-sale, Allowance for Credit Loss	(71)	$ (63)	(70)	$ (122)	$ (115)	$ (156)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,743		1,119
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(4,500)		(5,769)
Available for sale, Fair Value	116,119		110,363
U.S. and local government securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,271		4,383
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	19		10
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(257)		(323)
Available for sale, Fair Value	4,033		4,070
Non-U.S.
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	38,411		36,311
Debt Securities, Available-for-sale, Allowance for Credit Loss	(20)		(23)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	983		753
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(911)		(1,203)
Available for sale, Fair Value	38,463		35,838
Corporate and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	46,411		45,231
Debt Securities, Available-for-sale, Allowance for Credit Loss	(51)		(47)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	568		287
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,802)		(2,264)
Available for sale, Fair Value	45,126		43,207
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	29,854		29,158
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	173		69
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,530)		(1,979)
Available for sale, Fair Value	$ 28,497		$ 27,248