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	Jun. 30, 2024	Jun. 30, 2023
Accident and health insurance
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	$ 5,703	$ 5,020
Expected future gross premiums, discounted	3,867	3,602
Expected future benefits and expenses, undiscounted	3,854	3,350
Expected future benefits and expenses, discounted	2,567	2,326
Traditional life
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	1,042	696
Expected future gross premiums, discounted	715	489
Expected future benefits and expenses, undiscounted	1,456	1,008
Expected future benefits and expenses, discounted	$ 697	$ 539