Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 12,792	$ 27,956
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(201)	(518)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	36,192	39,789
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3,273)	(4,230)
Debt Securities, Available-for-sale, Unrealized Loss Position	48,984	67,745
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(3,474)	(4,748)
U.S. and local government securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	528	767
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(7)	(16)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,386	2,489
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(248)	(303)
Debt Securities, Available-for-sale, Unrealized Loss Position	2,914	3,256
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(255)	(319)
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	3,265	6,630
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(65)	(138)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	10,654	12,023
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(668)	(874)
Debt Securities, Available-for-sale, Unrealized Loss Position	13,919	18,653
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(733)	(1,012)
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	4,608	10,069
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(90)	(194)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	11,476	13,290
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(867)	(1,259)
Debt Securities, Available-for-sale, Unrealized Loss Position	16,084	23,359
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(957)	(1,453)
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	4,391	10,490
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(39)	(170)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	11,676	11,987
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,490)	(1,794)
Debt Securities, Available-for-sale, Unrealized Loss Position	16,067	22,477
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ (1,529)	$ (1,964)