Reserve for Future Policy Benefits and Contractholder Funds - Schedule of Undiscounted and Discounted Expected Gross Premiums and Expected Future Benefits and Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accident and health
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	$ 5,696	$ 5,339	$ 4,919
Expected future gross premiums, discounted	3,870	3,744	3,517
Expected future benefits and expenses, undiscounted	4,049	3,578	3,243
Expected future benefits and expenses, discounted	2,700	2,453	2,229
Traditional life
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	1,028	896	679
Expected future gross premiums, discounted	716	623	465
Expected future benefits and expenses, undiscounted	1,379	1,301	978
Expected future benefits and expenses, discounted	$ 698	$ 657	$ 524