10-K Investments (Current And Long-Term Fixed Maturity Securities, Available-For-Sale) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	$ 31,013	$ 29,015
Gross Unrealized Gains	52	76
Gross Unrealized Losses	(2,435)	(2,378)
Fixed Maturity Securities, Allowance for Credit Loss	(3)	(9)	$ (6)
Available-for-sale Securities	28,627	26,704
United States Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	1,906
Gross Unrealized Gains	0
Gross Unrealized Losses	(129)
Fixed Maturity Securities, Allowance for Credit Loss	0
Available-for-sale Securities	1,777	1,401
Government Sponsored Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	110
Gross Unrealized Gains	0
Gross Unrealized Losses	(8)
Fixed Maturity Securities, Allowance for Credit Loss	0
Available-for-sale Securities	102	78
Foreign Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	14
Gross Unrealized Gains	0
Gross Unrealized Losses	(2)
Fixed Maturity Securities, Allowance for Credit Loss	0
Available-for-sale Securities	12	274
States, Municipalities And Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	3,898
Gross Unrealized Gains	6
Gross Unrealized Losses	(325)
Fixed Maturity Securities, Allowance for Credit Loss	0
Available-for-sale Securities	3,579	4,143
Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	14,548
Gross Unrealized Gains	22
Gross Unrealized Losses	(1,156)
Fixed Maturity Securities, Allowance for Credit Loss	(1)
Available-for-sale Securities	13,413	12,529
Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	3,876
Gross Unrealized Gains	6
Gross Unrealized Losses	(438)
Fixed Maturity Securities, Allowance for Credit Loss	0
Available-for-sale Securities	3,444	2,663
Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	2,153
Gross Unrealized Gains	1
Gross Unrealized Losses	(188)
Fixed Maturity Securities, Allowance for Credit Loss	(2)
Available-for-sale Securities	1,964	1,878
Other Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost	4,508
Gross Unrealized Gains	17
Gross Unrealized Losses	(189)
Fixed Maturity Securities, Allowance for Credit Loss	0
Available-for-sale Securities	$ 4,336	3,738
Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		29,015	26,257
Gross Unrealized Gains		76	830
Gross Unrealized Losses		(2,378)	(182)
Fixed Maturity Securities, Allowance for Credit Loss		(9)	(6)
Available-for-sale Securities		26,704	26,899
Fixed Maturities [Member] | United States Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		1,502	1,443
Gross Unrealized Gains		2	7
Gross Unrealized Losses		(103)	(18)
Fixed Maturity Securities, Allowance for Credit Loss		0	0
Available-for-sale Securities		1,401	1,432
Fixed Maturities [Member] | Government Sponsored Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		82	65
Gross Unrealized Gains		1	4
Gross Unrealized Losses		(5)	(1)
Fixed Maturity Securities, Allowance for Credit Loss		0	0
Available-for-sale Securities		78	68
Fixed Maturities [Member] | Foreign Government Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		321	353
Gross Unrealized Gains		1	7
Gross Unrealized Losses		(46)	(13)
Fixed Maturity Securities, Allowance for Credit Loss		(2)	0
Available-for-sale Securities		274	347
Fixed Maturities [Member] | States, Municipalities And Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		4,389	5,321
Gross Unrealized Gains		19	310
Gross Unrealized Losses		(265)	(10)
Fixed Maturity Securities, Allowance for Credit Loss		0	0
Available-for-sale Securities		4,143	5,621
Fixed Maturities [Member] | Corporate Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		13,721	12,044
Gross Unrealized Gains		31	401
Gross Unrealized Losses		(1,218)	(78)
Fixed Maturity Securities, Allowance for Credit Loss		(5)	(4)
Available-for-sale Securities		12,529	12,363
Fixed Maturities [Member] | Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		2,978	2,492
Gross Unrealized Gains		9	48
Gross Unrealized Losses		(324)	(22)
Fixed Maturity Securities, Allowance for Credit Loss		0	0
Available-for-sale Securities		2,663	2,518
Fixed Maturities [Member] | Commercial Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		2,055	1,632
Gross Unrealized Gains		1	29
Gross Unrealized Losses		(176)	(16)
Fixed Maturity Securities, Allowance for Credit Loss		(2)	(2)
Available-for-sale Securities		1,878	1,643
Fixed Maturities [Member] | Other Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost or Amortized Cost		3,967	2,907
Gross Unrealized Gains		12	24
Gross Unrealized Losses		(241)	(24)
Fixed Maturity Securities, Allowance for Credit Loss		0	0
Available-for-sale Securities		$ 3,738	$ 2,907