Future Contract Benefits - Summary of Changes in Present Values of Expected Net Premiums and LFPB (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Present Value of Expected Future Policy Benefits
Net balance as of end-of-period	$ 41,852		$ 39,807
Reduction in liability, due to the net effect of changes in the cash flow assumptions	167	$ 96
Payout Annuities
Present Value of Expected Net Premiums
Balance as of beginning-of-year	0	0
Beginning balance at original discount rate	0	0
Effect of changes in cash flow assumptions			0	$ 0
Effect of actual variances from expected experience			0	0
Adjusted balance as of beginning-of-year			0	0
Issuances	0	0
Interest accrual	0	0
Net premiums collected	0	0
Flooring impact of LFPB	0	0
Ending balance at original discount rate	0	0
Effect of cumulative changes in discount rate assumptions	0	0
Balance as of end-of-period	0	0
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	2,009	2,085
Ending balance at original discount rate	2,229	2,266
Beginning balance at original discount rate	2,260	2,272
Effect of changes in cash flow assumptions			(8)	0
Effect of actual variances from expected experience			(11)	3
Adjusted balance as of beginning-of-year			2,241	2,275
Issuances	72	78
Interest accrual	66	65
Benefit payments	(150)	(152)
Effect of cumulative changes in discount rate assumptions	(177)	(147)
Balance as of end-of-period	2,052	2,119
Net balance as of end-of-period	2,052	2,119	2,009
Less: Reinsurance recoverables	1,461	1,578
Net balance as of end-of-period, net of reinsurance	$ 591	$ 541
Weighted-average duration of future policyholder benefit liability	8 years	9 years
Deferred profit liability	$ 88	$ 60
Payout Annuities | Cumulative Effect, Period of Adoption, Adjustment
Present Value of Expected Net Premiums
Balance as of beginning-of-year	0	0
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	(251)	(187)
Traditional Life
Present Value of Expected Net Premiums
Balance as of beginning-of-year	5,873	6,200
Beginning balance at original discount rate	6,148	6,348
Effect of changes in cash flow assumptions			(405)	28
Effect of actual variances from expected experience			(53)	(59)
Adjusted balance as of beginning-of-year			5,690	6,317
Issuances	213	289
Interest accrual	181	188
Net premiums collected	(564)	(596)
Flooring impact of LFPB	(8)	1
Ending balance at original discount rate	5,512	6,199
Effect of cumulative changes in discount rate assumptions	(81)	(19)
Balance as of end-of-period	5,431	6,180
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	9,647	10,041
Ending balance at original discount rate	9,292	10,104
Beginning balance at original discount rate	10,085	10,230
Effect of changes in cash flow assumptions			(573)	(68)
Effect of actual variances from expected experience			(48)	(70)
Adjusted balance as of beginning-of-year			9,464	$ 10,092
Issuances	213	289
Interest accrual	292	299
Benefit payments	(677)	(576)
Effect of cumulative changes in discount rate assumptions	(119)	14
Balance as of end-of-period	9,173	10,118
Net balance as of end-of-period	3,742	3,938	$ 3,774
Less: Reinsurance recoverables	290	388
Net balance as of end-of-period, net of reinsurance	$ 3,452	$ 3,550
Weighted-average duration of future policyholder benefit liability	8 years	9 years
Impact on net premiums, policyholder behavior	$ 38	$ 10
Impact on net premiums, mortality	15	49
Decrease in the liability based on policyholder behavior	51	4
Effect on liability based on mortality	3	74
Traditional Life | Cumulative Effect, Period of Adoption, Adjustment
Present Value of Expected Net Premiums
Balance as of beginning-of-year	(275)	(148)
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	$ (438)	$ (189)