Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 8,569	$ 57,189
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(176)	(4,115)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	53,950	14,991
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4,129)	(2,291)
Debt Securities, Available-for-sale, Unrealized Loss Position	62,519	72,180
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(4,305)	(6,406)
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	463	2,152
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)	(125)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,504	386
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(135)	(46)
Debt Securities, Available-for-sale, Unrealized Loss Position	2,967	2,538
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(144)	(171)
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	2,464	15,538
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(43)	(1,012)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	15,971	5,490
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(957)	(704)
Debt Securities, Available-for-sale, Unrealized Loss Position	18,435	21,028
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1,000)	(1,716)
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	2,866	25,687
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(51)	(1,793)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	20,334	4,190
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,194)	(552)
Debt Securities, Available-for-sale, Unrealized Loss Position	23,200	29,877
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1,245)	(2,345)
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	1,659	10,561
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(58)	(1,033)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,831	4,770
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,706)	(941)
Debt Securities, Available-for-sale, Unrealized Loss Position	15,490	15,331
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1,764)	(1,974)
Municipal
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1,117	3,251
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(15)	(152)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,310	155
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(137)	(48)
Debt Securities, Available-for-sale, Unrealized Loss Position	2,427	3,406
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (152)	$ (200)

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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