Reserves for Future Policy Benefits and Contract Owner Account Balances - Future Policy Benefits (Details) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($) yr	Dec. 31, 2023 USD ($) yr	Dec. 31, 2022 USD ($)
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits		$ 9,332	$ 9,560
Current discount rate		4.30%	4.20%
Liability for Claims and Claims Adjustment Expense		$ 595	$ 401	$ 398
Health Solutions Group
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Beginning balance		68	77
Beginning balance at original discount rate		71	84
Effect of change in cash flow assumptions		(1)	(6)
Effect of actual variances from expected experience		0	11
Adjusted balance at January 1		5	89
Interest accrual		0	2
Net premiums collected		(1)	(20)
Ending balance at original discount rate		4	71
Liability for Future Policy Benefit, Expected Net Premium, Period Increase (Decrease)		(65)
Effects of changes in discount rate assumptions		0	(3)
Ending balance		4	68
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Beginning balance		899	881
Beginning balance at original discount rate		918	913
Effect of change in cash flow assumptions		(12)	(8)
Effect of actual variances from expected experience		10	(16)
Adjusted balance at January 1		766	889
Issuances		131	136
Interest accrual		21	24
Benefit payments		(117)	(131)
Assessments		(150)
Ending balance at original discount rate		801	918
Effects of changes in discount rate assumptions		(29)	(19)
Ending balance		772	899
Net liability for future policy benefits		768	831
Less: Reinsurance recoverable		330	315
Net liability for future policy benefits, after reinsurance recoverable		438	516
Undiscounted, Expected future benefit payments		990	1,144
Undiscounted, Expected future gross premiums		11	271
Discounted, Expected future benefit payments		801	918	913
Discounted, Expected future gross premiums		$ 8	$ 214
Weighted average duration (in years) | yr		7	7
Interest accretion rate		4.00%	4.00%
Current discount rate		5.40%	4.90%
Liability for future policy benefit expected net premium reclassification	$ 17
liability for future policy benefit expected future policy benefit reclassification	17
Health Solutions Voluntary
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Beginning balance		$ 101	$ 97
Beginning balance at original discount rate		102	100
Effect of change in cash flow assumptions		(1)	6
Effect of actual variances from expected experience		40	8
Adjusted balance at January 1		206	114
Interest accrual		8	4
Net premiums collected		(34)	(16)
Ending balance at original discount rate		180	102
Liability for Future Policy Benefit, Expected Net Premium, Period Increase (Decrease)		65
Effects of changes in discount rate assumptions		(9)	(1)
Ending balance		171	101
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Beginning balance		307	285
Beginning balance at original discount rate		307	294
Effect of change in cash flow assumptions		(1)	13
Effect of actual variances from expected experience		54	9
Adjusted balance at January 1		510	316
Issuances		0	0
Interest accrual		18	14
Benefit payments		(41)	(23)
Assessments		150
Ending balance at original discount rate		487	307
Effects of changes in discount rate assumptions		(26)	0
Ending balance		461	307
Net liability for future policy benefits		290	206
Less: Reinsurance recoverable		9	0
Net liability for future policy benefits, after reinsurance recoverable		281	206
Undiscounted, Expected future benefit payments		881	668
Undiscounted, Expected future gross premiums		631	341
Discounted, Expected future benefit payments		487	307	294
Discounted, Expected future gross premiums		$ 427	$ 213
Weighted average duration (in years) | yr		14,000,000	14,000,000
Interest accretion rate		5.10%	5.20%
Current discount rate		5.70%	5.10%
Liability for future policy benefit expected net premium reclassification	(17)
liability for future policy benefit expected future policy benefit reclassification	$ (17)
Businesses Exited
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Beginning balance		$ 3,145	$ 4,244
Beginning balance at original discount rate		2,992	4,128
Effect of change in cash flow assumptions		110	(921)
Effect of actual variances from expected experience		(106)	(91)
Adjusted balance at January 1		2,996	3,116
Interest accrual		158	196
Net premiums collected		(312)	(320)
Ending balance at original discount rate		2,842	2,992
Effects of changes in discount rate assumptions		30	153
Ending balance		2,872	3,145
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Beginning balance		7,538	8,639
Beginning balance at original discount rate		7,404	8,644
Effect of change in cash flow assumptions		187	(805)
Effect of actual variances from expected experience		(90)	(123)
Adjusted balance at January 1		7,501	7,716
Issuances		14	17
Interest accrual		370	412
Benefit payments		(747)	(741)
Ending balance at original discount rate		7,138	7,404
Effects of changes in discount rate assumptions		(121)	134
Ending balance		7,017	7,538
Net liability for future policy benefits		4,145	4,392
Less: Reinsurance recoverable		4,056	4,342
Net liability for future policy benefits, after reinsurance recoverable		89	50
Discounted, Expected future benefit payments		$ 7,138	$ 7,404	$ 8,644
Weighted average duration (in years) | yr		8,000,000	8,000,000
Interest accretion rate		5.00%	4.90%
Current discount rate		5.60%	5.10%
Businesses Exited – Additional liability
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Beginning balance		$ 2,107
Effect of change in cash flow assumptions		(39)	$ (44)
Effect of actual variances from expected experience		14	(100)
Adjusted balance at January 1		1,976	1,963
Interest accrual		83	84
Benefit payments		(404)	(417)
Assessments		228	371
Ending balance		2,001	2,107
Net liability for future policy benefits		1,883	2,001
Less: Reinsurance recoverable		1,832	1,950
Net liability for future policy benefits, after reinsurance recoverable		51	51
Other
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits		367	394
business exited, other
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits		$ 1,284	$ 1,335