10-Q Investments (Net Investment Gains/Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Investment [Line Items]
Net gains (losses) on investments	$ (137)	$ (54)	$ (355)	$ (482)	$ (630)	$ 311	$ 184
Fixed Maturities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Realized Gain	13	8	34	44	52	170	175
Debt Securities, Available-for-sale, Realized Loss	(164)	(99)	(377)	(353)	(469)	(44)	(105)
Impairment recoveries (losses) recognized in income	2	(5)	(8)	(25)	(31)	1	(7)
Debt Securities, Available-for-sale, Realized Gain (Loss)	(149)	(96)	(351)	(334)	(448)	127	63
Equity Securities [Member]
Investment [Line Items]
Unrealized losses recognized on equity securities still held at the end of the period	0	(43)	(1)	(192)	(78)	2	133
Net realized gains (losses) recognized on equity securities sold during the period	2	4	5	(20)	102	73	(61)
Net gains (losses) on equity securities	2	(39)	4	(212)	(180)	(71)	194
Other Investments [Member]
Investment [Line Items]
Gross gains	86	95	91	126	96	293	18
Gross losses	(68)	(2)	(62)	(45)	(64)	(22)	0
Impairment recoveries (losses) recognized in income	(8)	(12)	(37)	(17)	(34)	(16)	(91)
Net gains (losses) on other investments	$ 10	$ 81	$ (8)	$ 64	$ (2)	$ 255	$ (73)