Future Contract Benefits - Summary of Changes in Present Values of Expected Net Premiums and LFPB (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Present Value of Expected LFPB
Net balance as of end-of-period	$ 41,409		$ 40,174
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 LFPB
Balance as of beginning-of-year	2,084	2,003
Beginning balance of original discount rate	2,271	2,266
Effect of changes in cash flow assumptions			0	17
Effect of actual variances from expected experience			3	(1)
Adjusted balance as of beginning-of-year	2,274	2,282
Issuances	78	83
Interest accrual	65	64
Benefit payments	(152)	(142)
Ending balance at original discount rate	2,265	2,287
Effect of cumulative changes in discount rate assumptions	(147)	(344)
Balance as of end-of-period	2,118	1,943
Net balance as of end-of-period	2,118	1,943	2,084
Less: reinsurance recoverables	1,590	11
Net balance as of end-of-period, net of reinsurance	$ 528	$ 1,932
Weighted-average duration of future policyholder benefit liability (years)	9 years	9 years
Deferred profit liability	$ 60	$ 38
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 LFPB
Balance as of beginning-of-year	(187)	(263)
Traditional Life
Present Value of Expected Net Premiums
Balance as of beginning-of-year	6,084	5,896
Beginning balance at original discount rate	6,236	6,480
Effect of changes in cash flow assumptions			(3)	(5)
Effect of actual variances from expected experience			(29)	(262)
Adjusted balance as of beginning-of-year			6,204	6,213
Issuances	289	460
Interest accrual	184	176
Net premiums collected	(581)	(588)
Flooring impact of LFPB	1	3
Ending balance at original discount rate	6,097	6,264
Effect of cumulative changes in discount rate assumptions	(23)	(527)
Balance as of end-of-period	6,074	5,737
Present Value of Expected LFPB
Balance as of beginning-of-year	9,637	9,086
Beginning balance of original discount rate	9,839	9,879
Effect of changes in cash flow assumptions			(105)	(21)
Effect of actual variances from expected experience			(41)	(289)
Adjusted balance as of beginning-of-year	9,693	9,569
Issuances	289	460
Interest accrual	285	270
Benefit payments	(530)	(479)
Ending balance at original discount rate	9,737	9,820
Effect of cumulative changes in discount rate assumptions	(3)	(831)
Balance as of end-of-period	9,734	8,989
Net balance as of end-of-period	3,660	3,252	3,553
Less: reinsurance recoverables	215	232
Net balance as of end-of-period, net of reinsurance	$ 3,445	$ 3,020
Weighted-average duration of future policyholder benefit liability (years)	9 years	10 years
Traditional Life | Cumulative effect from adoption of new accounting standards
Present Value of Expected Net Premiums
Balance as of beginning-of-year	$ (152)	$ (584)
Present Value of Expected LFPB
Balance as of beginning-of-year	(202)	(793)
Group Protection
Present Value of Expected Net Premiums
Effect of cumulative changes in discount rate assumptions			(490)	(597)
Present Value of Expected LFPB
Balance as of beginning-of-year	5,689	5,462
Beginning balance of original discount rate	6,179	6,059
Effect of changes in cash flow assumptions			(2)	(27)
Effect of actual variances from expected experience			(278)	$ (233)
Adjusted balance as of beginning-of-year	5,899	5,799
Issuances	1,236	1,267
Interest accrual	138	122
Benefit payments	(1,125)	(1,095)
Ending balance at original discount rate	6,148	6,093
Effect of cumulative changes in discount rate assumptions	(375)	(720)
Balance as of end-of-period	5,773	5,373
Net balance as of end-of-period	5,773		$ 5,689
Less: reinsurance recoverables	4,153	117
Net balance as of end-of-period, net of reinsurance	$ 1,620	$ 5,256
Weighted-average duration of future policyholder benefit liability (years)	5 years	5 years