Other Insurance Liabilities and Separate Accounts - Changes in Liability for Future Policy Benefits (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Large Case Pensions
Present value of expected future policy benefits
Liability for future policy benefits, beginning of period - current discount rate	$ 2,253	$ 3,034
Beginning liability for future policy benefits at original (locked-in) discount rate	2,425	2,650
Effect of changes in cash flow assumptions			$ 0	$ 0
Effect of actual variances from expected experience			1	(26)
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			2,426	2,624
Issuances	8	4
Interest accrual (using locked-in discount rate)	74	80
Benefit payments (actual)	(210)	(220)
Ending liability for future policy benefits at original (locked-in) discount rate	2,298	2,488
Effect of changes in discount rate assumptions	(247)	(205)
Liability for future policy benefits, end of period - current discount rate	2,051	2,283
Net liability for future policy benefits	2,051	2,283
Less: Reinsurance recoverable	0	0			$ 0
Net liability for future policy benefits, net of reinsurance recoverable	2,051	2,283			3,647
Long-Term Care
Present value of expected net premiums
Liability for future policy benefits, beginning of period - current discount rate	300	389
Beginning liability for future policy benefits at original (locked-in) discount rate	302	323
Effect of changes in cash flow assumptions			0	(14)
Effect of actual variances from expected experience			7	13
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			309	322
Interest accrual (using locked-in discount rate)	11	11
Net premiums (actual)	(29)	(30)
Ending liability for future policy benefits at original (locked-in) discount rate	291	303
Effect of changes in discount rate assumptions	(12)	(5)
Liability for future policy benefits, end of period - current discount rate	279	298
Present value of expected future policy benefits
Liability for future policy benefits, beginning of period - current discount rate	1,566	1,991
Beginning liability for future policy benefits at original (locked-in) discount rate	1,613	1,480
Effect of changes in cash flow assumptions			0	99
Effect of actual variances from expected experience			9	15
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			$ 1,622	$ 1,594
Issuances	0	0
Interest accrual (using locked-in discount rate)	61	60
Benefit payments (actual)	(53)	(48)
Ending liability for future policy benefits at original (locked-in) discount rate	1,630	1,606
Effect of changes in discount rate assumptions	(146)	(78)
Liability for future policy benefits, end of period - current discount rate	1,484	1,528
Net liability for future policy benefits	1,205	1,230
Less: Reinsurance recoverable	0	0			0
Net liability for future policy benefits, net of reinsurance recoverable	$ 1,205	$ 1,230			$ 1,695