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	$ 42,128		$ 40,002
Reduction in liability, due to the net effect of changes in the cash flow assumptions	161	$ 102
Actual effect on liability, based on policyholder behavior		66
Actual effect on liability, based on mortality		25
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 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 changes in cash flow assumptions			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	2,008	2,084
Beginning balance of original discount rate	2,259	2,271
Effect of changes in cash flow assumptions			(8)	0
Effect of actual variances from expected experience			(11)	3
Effect of cumulative changes in discount rate assumptions	(176)	(147)
Adjusted balance as of beginning-of-year			2,240	2,274
Issuances	73	78
Interest accrual	66	65
Benefit payments	(151)	(152)
Ending balance at original discount rate	2,228	2,265
Balance as of end-of-period	2,052	2,118
Net balance as of end-of-period	2,052	2,118	2,008
Less: Reinsurance recoverables	1,477	1,590
Net balance as of end-of-period, net of reinsurance	$ 575	$ 528
Weighted-average duration of future policyholder benefit liability (years)	8 years	9 years
Deferred profit liability	$ 88	$ 60
Payout Annuities | Cumulative effect from adoption of new accounting standards
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	5,751	6,084
Beginning balance at original discount rate	6,028	6,236
Effect of actual variances from expected experience			(21)	(29)
Adjusted balance as of beginning-of-year			5,611	6,204
Issuances	213	289
Interest accrual	177	184
Net premiums collected	(551)	(581)
Flooring impact of LFPB	(5)	1
Ending balance at original discount rate	5,445	6,097
Effect of changes in cash flow assumptions			(396)	(3)
Effect of cumulative changes in discount rate assumptions	(84)	(23)
Balance as of end-of-period	5,361	6,074
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	9,255	9,637
Beginning balance of original discount rate	9,701	9,839
Effect of changes in cash flow assumptions			(557)	(105)
Effect of actual variances from expected experience			(2)	(41)
Effect of cumulative changes in discount rate assumptions	(130)	(3)
Adjusted balance as of beginning-of-year			9,142	9,693
Issuances	213	289
Interest accrual	279	285
Benefit payments	(640)	(530)
Ending balance at original discount rate	8,994	9,737
Balance as of end-of-period	8,864	9,734
Net balance as of end-of-period	3,503	3,660	3,504
Less: Reinsurance recoverables	167	215
Net balance as of end-of-period, net of reinsurance	$ 3,336	$ 3,445
Weighted-average duration of future policyholder benefit liability (years)	9 years	9 years
Expected effect on liability, based on policyholder behavior		$ 44
Expected effect on liability, based on mortality		15
Traditional Life | Cumulative effect from adoption of new accounting standards
Present Value of Expected Net Premiums
Balance as of beginning-of-year	$ (277)	(152)
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	(446)	(202)
Group Protection
Present Value of Expected Net Premiums
Effect of cumulative changes in discount rate assumptions			(550)	(490)
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	5,628	5,689
Beginning balance of original discount rate	6,178	6,179
Effect of changes in cash flow assumptions			(66)	(2)
Effect of actual variances from expected experience			(191)	(278)
Effect of cumulative changes in discount rate assumptions	(371)	(375)
Adjusted balance as of beginning-of-year			5,921	$ 5,899
Issuances	1,176	1,236
Interest accrual	148	138
Benefit payments	(1,080)	(1,125)
Ending balance at original discount rate	6,165	6,148
Balance as of end-of-period	5,794	5,773
Net balance as of end-of-period	5,794		$ 5,628
Less: Reinsurance recoverables	4,213	4,153
Net balance as of end-of-period, net of reinsurance	$ 1,581	$ 1,620
Weighted-average duration of future policyholder benefit liability (years)	5 years	5 years