Future Contract Benefits - Summary of Changes in Present Values of LFPB (UL and Other) (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
Actual effect on liability, based on mortality		$ 25
UL and Other
Present Value of Expected Future Policy Benefits
Balance as of beginning-of-year	$ 16,663	15,752
Effect of cumulative changes in discount rate assumptions	(1,043)	(619)	$ (1,515)	$ (853)
Balance as of beginning-of-year, excluding shadow balance in AOCI	18,178	16,605
Effect of changes in cash flow assumptions			120	207
Effect of actual variances from expected experience			$ 182	$ 170
Adjusted balance as of beginning-of-year	18,480	16,982
Interest accrual	686	623
Net assessments collected	1,012	946
Benefit payments	(850)	(718)
Balance as of end-of-year, excluding shadow balance in AOCI	19,328	17,833
Balance as of end-of-period	18,285	17,215
Less: Reinsurance recoverables	11,532	10,499
Net balance as of end-of-period, net of reinsurance	$ 6,753	$ 6,715
Weighted-average duration of future policyholder benefit liability (years)	16 years	16 years
Actual effect on liability, based on mortality	$ 193	$ 160
Effect of actual variances from expected experience, net of reinsurance	$ 12	$ 110