10-Q Fair Value (Carrying and Fair Value By Level of Financial Instruments Not Recorded At Fair Value On Consolidated Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	$ 6,118	$ 5,685	$ 5,225
Convertible debentures		63
Short-term borrowings	0	265	275
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	6,016	5,582	5,087
Short-term FHLB borrowings outstanding		265	275
Commercial paper			300
Notes	24,844	23,786	22,384
Convertible debentures		63	72
Short-term borrowings		265
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	6,016	5,582	5,087
Short-term FHLB borrowings outstanding		265	275
Commercial paper			300
Notes	21,815	21,861	25,150
Convertible debentures		463	687
Short-term borrowings		265
Fair Value, Recurring [Member] | Level I [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0
Short-term FHLB borrowings outstanding			0
Notes	0	0
Convertible debentures		0
Short-term borrowings		0
Fair Value, Recurring [Member] | Level II [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	0	0	0
Short-term FHLB borrowings outstanding		265	275
Commercial paper			300
Notes	21,815	21,861	25,150
Convertible debentures		463	687
Short-term borrowings		265
Fair Value, Recurring [Member] | Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	6,016	5,582	5,087
Short-term FHLB borrowings outstanding		0	0
Commercial paper			0
Notes	$ 0	0	0
Convertible debentures		0	$ 0
Short-term borrowings		$ 0