Future Contract Benefits - Summary of Changes in Present Values of LFPB (Group Protection) (Details) - Group Protection - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Present Value of Expected LFPB
Balance as of beginning-of-year	$ 5,689	$ 5,462
Effect of cumulative changes in discount rate assumptions			$ (490)	$ (597)
Beginning balance at 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
Less: reinsurance recoverables	120	117
Net balance as of end-of-period, net of reinsurance	$ 5,653	$ 5,256
Weighted-average duration of future policyholder benefit liability	5 years	5 years