Other Insurance Liabilities and Separate Accounts - Changes in Liability for Future Policy Benefits (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Present value of expected future policy benefits
Effect of changes in discount rate assumptions	$ (19)	$ (26)	$ (23)
Large Case Pensions
Present value of expected future policy benefits
Liability for future policy benefits, beginning of the period - current discount rate	2,139	2,253
Beginning liability for future policy benefits at original (locked-in) discount rate	2,251	2,425
Effect of changes in cash flow assumptions			0	$ 0
Effect of actual variances from expected experience			(20)	1
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			2,231	2,426
Issuances	26	8
Interest accrual (using locked-in discount rate)	69	74
Benefit payments (actual)	(192)	(210)
Ending liability for future policy benefits at original (locked-in) discount rate	2,134	2,298
Effect of changes in discount rate assumptions	(90)	(247)
Liability for future policy benefits, end of the period - current discount rate	2,044	2,051
Net liability for future policy benefits	2,044	2,051
Less: Reinsurance recoverable	0	0
Net liability for future policy benefits, net of reinsurance recoverable	2,044	2,051
Long-Term Care
Present value of expected net premiums
Liability for future policy benefits, beginning of the period - current discount rate	293	300
Beginning liability for future policy benefits at original (locked-in) discount rate	288	302
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			12	7
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			300	309
Interest accrual (using locked-in discount rate)	11	11
Net premiums (actual)	(29)	(29)
Ending liability for future policy benefits at original (locked-in) discount rate	282	291
Effect of changes in discount rate assumptions	6	(12)
Liability for future policy benefits, end of the period - current discount rate	288	279
Present value of expected future policy benefits
Liability for future policy benefits, beginning of the period - current discount rate	1,640	1,566
Beginning liability for future policy benefits at original (locked-in) discount rate	1,632	1,613
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			5	9
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			$ 1,637	$ 1,622
Issuances	0	0
Interest accrual (using locked-in discount rate)	61	61
Benefit payments (actual)	(55)	(53)
Ending liability for future policy benefits at original (locked-in) discount rate	1,643	1,630
Effect of changes in discount rate assumptions	12	(146)
Liability for future policy benefits, end of the period - current discount rate	1,655	1,484
Net liability for future policy benefits	1,367	1,205
Less: Reinsurance recoverable	0	0
Net liability for future policy benefits, net of reinsurance recoverable	$ 1,367	$ 1,205