Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Reconciliation of the Net Incurred and Paid Claims Development to Reserve for Property and Casualty Insurance Claims and Claims Expense (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Reserve for life-contingent benefits:
Gross reserve for future policy benefits	$ 41,917	$ 39,858
Accident and health insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	252
Gross reserve for future policy benefits	269
Group and individual accident and health short-duration contracts | Accident and health insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	186
Recoverables	17
Long-duration accident and health insurance | Accident and health insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	45
Long-duration traditional life insurance | Accident and health insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	7
Other contracts | Accident and health insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	5
ULAE | Accident and health insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	$ 9