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) - Accident and health insurance $ in Millions	Dec. 31, 2023 USD ($)
Reserve for life-contingent benefits:
Net outstanding liabilities	$ 1,227
Gross reserve for future policy benefits	1,347
Group and individual accident and health short-duration contracts
Reserve for life-contingent benefits:
Net outstanding liabilities	175
Recoverables	37
Long-duration accident and health insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	684
Long-duration traditional life insurance
Reserve for life-contingent benefits:
Net outstanding liabilities	330
Other contracts
Reserve for life-contingent benefits:
Net outstanding liabilities	29
Other accident and health short-duration contracts
Reserve for life-contingent benefits:
Recoverables	0
Insurance lines other than short-duration
Reserve for life-contingent benefits:
Recoverables	83
Unallocated loss adjustment expenses (“ULAE”)
Reserve for life-contingent benefits:
Net outstanding liabilities	9
Recoverables	$ 0