10-Q Fair Value (Reconciliation Of The Beginning And Ending Balances Of Assets Measured At Fair Value On A Recurring Basis Using Level III Inputs) (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
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 544	$ 467	$ 581	$ 449	$ 449	$ 392	$ 397
Gains (losses) recognized in net income	$ 0	$ 0	$ (11)	$ 1	$ (1)	$ 19	$ (22)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net losses on financial instruments	Net losses on financial instruments	Net losses on financial instruments	Net losses on financial instruments	Net losses on financial instruments	Net losses on financial instruments	Net losses on financial instruments
Gains (losses) recognized in accumulated other comprehensive loss/income	$ 1	$ 18	$ 7	$ 16	$ (17)	$ 3	$ (5)
Purchases	80	95	98	345	443	216	101
Sales	(19)	(29)	(80)	(221)	(242)	(22)	(41)
Settlements	(12)	(10)	(18)	(42)	(41)	(157)	(46)
Transfers Into Level III	8	0	43	9	9	3	10
Transfers out of Level III	(2)	(6)	(20)	(22)	(19)	(5)	(2)
Ending balance	600	535	600	535	581	449	392
Change in unrealized losses included in net income related to assets still held	0	0	(4)	1	0	18	(19)
Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	103	155	137	336	336	325	303
Gains (losses) recognized in net income	(2)	0	(8)	0	0	2	(3)
Gains (losses) recognized in accumulated other comprehensive loss/income	1	1	5	(1)	(1)	3	(5)
Purchases	17	15	22	40	56	179	85
Sales	(2)	(26)	(43)	(201)	(210)	(18)	(19)
Settlements	(12)	(10)	(18)	(42)	(41)	(157)	(44)
Transfers Into Level III	6	0	35	9	9	3	10
Transfers out of Level III	(1)	(6)	(20)	(12)	(12)	(1)	(2)
Ending balance	110	129	110	129	137	336	325
Change in unrealized losses included in net income related to assets still held	0	0	0	0	0	0	0
Residential Mortgage-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	0	0	5	5	2	2
Gains (losses) recognized in net income	0	0	0	0	0	0	0
Gains (losses) recognized in accumulated other comprehensive loss/income	0	0	0	0	0	0	0
Purchases	0	0	0	0	0	4	0
Sales	0	0	0	0	0	0	0
Settlements	0	0	0	0	0	0	0
Transfers Into Level III	2	0	2	0	0	0	0
Transfers out of Level III	0	0	0	(5)	(5)	(1)	0
Ending balance	2	0	2	0	0	5	2
Change in unrealized losses included in net income related to assets still held	0	0	0	0	0	0	0
Other Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	366	218	356	19	19	5	7
Gains (losses) recognized in net income	0	0	0	0	(1)	0	0
Gains (losses) recognized in accumulated other comprehensive loss/income	0	17	2	17	(16)	0	0
Purchases	60	77	72	281	370	17	0
Sales	(6)	(1)	(17)	(1)	(14)	0	0
Settlements	0	0	0	0	0	0	(2)
Transfers Into Level III	0	0	6	0	0	0	0
Transfers out of Level III	(1)	0	0	(5)	(2)	(3)	0
Ending balance	419	311	419	311	356	19	5
Change in unrealized losses included in net income related to assets still held	0	0	0	0	0	0	0
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	75	94	88	89	89	60	85
Gains (losses) recognized in net income	2	0	(3)	1	0	17	(19)
Gains (losses) recognized in accumulated other comprehensive loss/income	0	0	0	0	0	0	0
Purchases	3	3	4	24	17	16	16
Sales	(11)	(2)	(20)	(19)	(18)	(4)	(22)
Settlements	0	0	0	0	0	0	0
Transfers Into Level III	0	0	0	0	0	0	0
Transfers out of Level III	0	0	0	0	0	0	0
Ending balance	69	95	69	95	88	89	60
Change in unrealized losses included in net income related to assets still held	$ 0	$ 0	$ (4)	$ 1	$ 0	$ 18	$ (19)