Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Rollforward of Reserve 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 net premiums
Beginning balance	$ 2,013	$ 1,702
Beginning balance at original discount rate	2,067	1,795
Effect of changes in cash flow assumptions			$ 0	$ 0
Effect of actual variances from expected experience			(33)	(37)
Adjusted beginning balance			2,034	1,758
Issuances	262	216
Interest accrual	23	15
Net premiums collected	(114)	(107)
Ending balance at original discount rate	2,205	1,882
Effect of changes in discount rate assumptions	(90)	(67)
Ending balance	2,115	1,815
Present value of expected future policy benefits
Beginning balance	3,110	2,753
Beginning balance at original discount rate	3,151	2,850
Effect of changes in cash flow assumptions			(6)	0
Effect of actual variances from expected experience			(39)	(43)
Adjusted beginning balance			3,106	2,807
Issuances	263	215
Interest accrual	34	25
Benefit payments	(114)	(111)
Ending balance at original discount rate	3,289	2,936
Effect of changes in discount rate assumptions	(108)	(54)
Ending balance	3,181	2,882
Net reserve for future policy benefits	1,066	1,067
Less: reinsurance recoverables	81	78
Net reserve for future policy benefits, after reinsurance recoverables	985	989
Reserves related to short-duration contracts	259	271
Accident and health insurance
Present value of expected net premiums
Beginning balance	1,688	1,464
Beginning balance at original discount rate	1,737	1,549
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			(44)	(42)
Adjusted beginning balance			1,693	1,507
Issuances	230	199
Interest accrual	18	12
Net premiums collected	(98)	(95)
Ending balance at original discount rate	1,843	1,623
Effect of changes in discount rate assumptions	(81)	(62)
Ending balance	1,762	1,561
Present value of expected future policy benefits
Beginning balance	2,453	2,229
Beginning balance at original discount rate	2,495	2,316
Effect of changes in cash flow assumptions			(6)	0
Effect of actual variances from expected experience			(47)	(47)
Adjusted beginning balance			2,442	2,269
Issuances	230	199
Interest accrual	25	19
Benefit payments	(102)	(99)
Ending balance at original discount rate	2,595	2,388
Effect of changes in discount rate assumptions	(86)	(53)
Ending balance	2,509	2,335
Net reserve for future policy benefits	747	774
Less: reinsurance recoverables	80	76
Net reserve for future policy benefits, after reinsurance recoverables	667	698
Traditional life
Present value of expected net premiums
Beginning balance	325	238
Beginning balance at original discount rate	330	246
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			11	5
Adjusted beginning balance			341	251
Issuances	32	17
Interest accrual	5	3
Net premiums collected	(16)	(12)
Ending balance at original discount rate	362	259
Effect of changes in discount rate assumptions	(9)	(5)
Ending balance	353	254
Present value of expected future policy benefits
Beginning balance	657	524
Beginning balance at original discount rate	656	534
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			8	4
Adjusted beginning balance			$ 664	$ 538
Issuances	33	16
Interest accrual	9	6
Benefit payments	(12)	(12)
Ending balance at original discount rate	694	548
Effect of changes in discount rate assumptions	(22)	(1)
Ending balance	672	547
Net reserve for future policy benefits	319	293
Less: reinsurance recoverables	1	2
Net reserve for future policy benefits, after reinsurance recoverables	$ 318	$ 291