Other Insurance Liabilities and Separate Accounts - Changes in Liability for Future Policy Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Present value of expected future policy benefits
Effect of changes in discount rate assumptions	$ (23)		$ (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			(8)	3
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			2,243	2,428
Issuances	20	5
Interest accrual (using locked-in discount rate)	24	25
Benefit payments (actual)	(63)	(73)
Ending liability for future policy benefits at original (locked-in) discount rate	2,224	2,385
Effect of changes in discount rate assumptions	(151)	(115)
Liability for future policy benefits, end of the period - current discount rate	2,073	2,270
Net liability for future policy benefits	2,073	2,270
Less: Reinsurance recoverable	0	0
Net liability for future policy benefits, net of reinsurance recoverable	2,073	2,270
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			5	0
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			293	302
Interest accrual (using locked-in discount rate)	4	4
Net premiums (actual)	(10)	(10)
Ending liability for future policy benefits at original (locked-in) discount rate	287	296
Effect of changes in discount rate assumptions	(2)	5
Liability for future policy benefits, end of the period - current discount rate	285	301
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			0	(2)
Adjusted beginning liability for future policy benefits - original (locked-in) discount rate			$ 1,632	$ 1,611
Issuances	0	0
Interest accrual (using locked-in discount rate)	21	20
Benefit payments (actual)	(18)	(18)
Ending liability for future policy benefits at original (locked-in) discount rate	1,635	1,613
Effect of changes in discount rate assumptions	(41)	12
Liability for future policy benefits, end of the period - current discount rate	1,594	1,625
Net liability for future policy benefits	1,309	1,324
Less: Reinsurance recoverable	0	0
Net liability for future policy benefits, net of reinsurance recoverable	$ 1,309	$ 1,324