10-K Investments (Amortized Cost And Fair Value Of Fixed Maturity Securities, By Contractual Maturity) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost	$ 757
Due after one year through five years, Amortized Cost	8,146
Due after five years through ten years, Amortized Cost	10,062
Due after ten years, Amortized Cost	6,019
Mortgage-backed securities, Amortized Cost	6,029
Cost or Amortized Cost	31,013	$ 29,015
Due in one year or less, Estimated Fair Value	749
Due after one year through five years, Estimated Fair Value	7,729
Due after five years through ten years, Estimated Fair Value	9,300
Due after ten years, Estimated Fair Value	5,441
Mortgage-backed securities, Estimated Fair Value	5,408
Available-for-sale Securities	$ 28,627	26,704
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, Amortized Cost		726
Due after one year through five years, Amortized Cost		7,489
Due after five years through ten years, Amortized Cost		9,512
Due after ten years, Amortized Cost		6,255
Mortgage-backed securities, Amortized Cost		5,033
Cost or Amortized Cost		29,015	$ 26,257
Due in one year or less, Estimated Fair Value		720
Due after one year through five years, Estimated Fair Value		7,095
Due after five years through ten years, Estimated Fair Value		8,703
Due after ten years, Estimated Fair Value		5,645
Mortgage-backed securities, Estimated Fair Value		4,541
Available-for-sale Securities		$ 26,704	$ 26,899