Investments (Schedule Of Amortized Cost and Fair Value of Available-for-Sale Securities) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 114,930	$ 115,083
Debt Securities, Available-for-sale, Allowance for Credit Loss	(63)	(70)	$ (115)	$ (156)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,281	1,119
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(5,025)	(5,769)
Available for sale, Fair Value	111,123	110,363
U.S. and local government securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,268	4,383
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	17	10
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(260)	(323)
Available for sale, Fair Value	4,025	4,070
Non-U.S.
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	36,574	36,311
Debt Securities, Available-for-sale, Allowance for Credit Loss	(22)	(23)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	810	753
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,060)	(1,203)
Available for sale, Fair Value	36,302	35,838
Corporate and asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	45,105	45,231
Debt Securities, Available-for-sale, Allowance for Credit Loss	(41)	(47)
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	309	287
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(2,093)	(2,264)
Available for sale, Fair Value	43,280	43,207
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	28,983	29,158
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	145	69
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before tax	(1,612)	(1,979)
Available for sale, Fair Value	$ 27,516	$ 27,248

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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