Long-duration insurance contracts - Summary of weighted average discount rates, interest accretion rates established at contract inception and the average contract duration (Detail)	Jun. 30, 2023	Jun. 30, 2022
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Weighted average discount rate	5.30%	4.70%
Weighted average accretion rate	4.80%	4.90%
Weighted average duration (in years)	18 years	18 years
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Weighted average discount rate	5.00%	4.50%
Weighted average accretion rate	3.30%	3.30%
Weighted average duration (in years)	14 years	14 years