Future Contract Benefits - Summary of Changes in Present Values of LFPB (UL and Other) (Details) - UL and Other - 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
Balance as of beginning-of-year	$ 16,062	$ 15,000
Effect of cumulative changes in shadow balance in AOCI	(2,174)	(1,863)	$ (2,673)	$ (2,222)
Balance as of beginning-of-year, excluding shadow balance in AOCI	18,735	17,222
Effect of changes in cash flow assumptions			121	244
Effect of actual variances from expected experience			$ 183	$ 170
Adjusted balance as of beginning-of-year	19,039	17,636
Interest accrual	700	639
Net assessments collected	922	860
Benefit payments	(850)	(718)
Balance as of end-of-year, excluding shadow balance in AOCI	19,811	18,417
Balance as of end-of-period	17,637	16,554
Less: Reinsurance recoverables	5,414	5,139
Net balance as of end-of-period, net of reinsurance	$ 12,223	$ 11,415
Weighted-average duration of future policyholder benefit liability	16 years	16 years
Unfavorable impact to the liability due to mortality	$ (193)	$ (160)
Effect of actual variances from expected experience, net of reinsurance	$ 88	$ 115