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, 2023	Jun. 30, 2022
Accident and health insurance
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	$ 5,020	$ 5,133
Expected future gross premiums, discounted	3,602	3,833
Expected future benefits and expenses, undiscounted	3,350	3,416
Expected future benefits and expenses, discounted	2,326	2,433
Traditional life
Liability for Future Policy Benefit, Activity [Line Items]
Expected future gross premiums, undiscounted	696	636
Expected future gross premiums, discounted	489	457
Expected future benefits and expenses, undiscounted	1,008	956
Expected future benefits and expenses, discounted	$ 539	$ 561