Long-duration insurance contracts - Summary of undiscounted and discounted expected future gross premiums to be collected and undiscounted expected future benefits for periodic payment annuities and life and health insurance (Detail) - USD ($) $ in Millions	Jun. 30, 2023	Jun. 30, 2022
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future benefits	$ 31,232	$ 31,084
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Undiscounted expected future gross premiums	108,089	107,647
Discounted expected future gross premiums	65,599	64,832
Undiscounted expected future benefits	$ 103,012	$ 102,305