Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 3,916	$ 8,569
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(45)	(176)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	45,457	53,950
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3,271)	(4,129)
Debt Securities, Available-for-sale, Unrealized Loss Position	49,373	62,519
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(3,316)	(4,305)
U.S. Treasury / Agency
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	463
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(9)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,677	2,504
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(98)	(135)
Debt Securities, Available-for-sale, Unrealized Loss Position	1,677	2,967
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(98)	(144)
Non-U.S.
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,706	2,464
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(26)	(43)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,628	15,971
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(734)	(957)
Debt Securities, Available-for-sale, Unrealized Loss Position	15,334	18,435
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(760)	(1,000)
Corporate and asset-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,511	2,866
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(13)	(51)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	15,280	20,334
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(959)	(1,194)
Debt Securities, Available-for-sale, Unrealized Loss Position	16,791	23,200
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(972)	(1,245)
Mortgage-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	664	1,659
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(5)	(58)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,684	13,831
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,366)	(1,706)
Debt Securities, Available-for-sale, Unrealized Loss Position	14,348	15,490
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1,371)	(1,764)
Municipal
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	35	1,117
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	(15)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,188	1,310
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(114)	(137)
Debt Securities, Available-for-sale, Unrealized Loss Position	1,223	2,427
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (115)	$ (152)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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