Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Rollforward of Reserve for Future Policy Benefits (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Present value of expected net premiums
Beginning balance	$ 1,702	$ 2,039
Beginning balance at original discount rate	1,795	1,819
Effect of changes in cash flow assumptions			$ 22	$ 0
Effect of actual variances from expected experience			0	(103)
Adjusted beginning balance			1,817	1,716
Issuances	431	308
Interest accrual	56	41
Net premiums collected	(297)	(288)
Ending balance at original discount rate	2,007	1,777
Effect of changes in discount rate assumptions	(132)	(104)
Ending balance	1,875	1,673
Present value of expected future policy benefits
Beginning balance	2,753	3,469
Beginning balance at original discount rate	2,850	2,937
Effect of changes in cash flow assumptions			51	(44)
Effect of actual variances from expected experience			(21)	(94)
Adjusted beginning balance			2,880	2,799
Issuances	436	301
Interest accrual	93	77
Benefit payments	(327)	(347)
Ending balance at original discount rate	3,082	2,830
Effect of changes in discount rate assumptions	(164)	(116)
Ending balance	2,918	2,714
Net reserve for future policy benefits	1,043	1,041
Less: reinsurance recoverables	84	77
Net reserve for future policy benefits, after reinsurance recoverables	959	964
Reserves related to short-duration contracts	266	277
Accident and health insurance
Present value of expected net premiums
Beginning balance	1,464	1,785
Beginning balance at original discount rate	1,549	1,604
Effect of changes in cash flow assumptions			(12)	0
Effect of actual variances from expected experience			(4)	(138)
Adjusted beginning balance			1,533	1,466
Issuances	378	301
Interest accrual	48	36
Net premiums collected	(260)	(254)
Ending balance at original discount rate	1,699	1,549
Effect of changes in discount rate assumptions	(113)	(96)
Ending balance	1,586	1,453
Present value of expected future policy benefits
Beginning balance	2,229	2,796
Beginning balance at original discount rate	2,316	2,426
Effect of changes in cash flow assumptions			21	(44)
Effect of actual variances from expected experience			(24)	(120)
Adjusted beginning balance			2,313	2,262
Issuances	368	293
Interest accrual	75	62
Benefit payments	(297)	(294)
Ending balance at original discount rate	2,459	2,323
Effect of changes in discount rate assumptions	(126)	(105)
Ending balance	2,333	2,218
Net reserve for future policy benefits	747	765
Less: reinsurance recoverables	82	75
Net reserve for future policy benefits, after reinsurance recoverables	665	690
Traditional life
Present value of expected net premiums
Beginning balance	238	254
Beginning balance at original discount rate	246	215
Effect of changes in cash flow assumptions			34	0
Effect of actual variances from expected experience			4	35
Adjusted beginning balance			284	250
Issuances	53	7
Interest accrual	8	5
Net premiums collected	(37)	(34)
Ending balance at original discount rate	308	228
Effect of changes in discount rate assumptions	(19)	(8)
Ending balance	289	220
Present value of expected future policy benefits
Beginning balance	524	673
Beginning balance at original discount rate	534	511
Effect of changes in cash flow assumptions			30	0
Effect of actual variances from expected experience			3	26
Adjusted beginning balance			$ 567	$ 537
Issuances	68	8
Interest accrual	18	15
Benefit payments	(30)	(53)
Ending balance at original discount rate	623	507
Effect of changes in discount rate assumptions	(38)	(11)
Ending balance	585	496
Net reserve for future policy benefits	296	276
Less: reinsurance recoverables	2	2
Net reserve for future policy benefits, after reinsurance recoverables	$ 294	$ 274