Long-duration insurance contracts - Summary of weighted average discount rates, interest accretion rates established at contract inception and the average contract duration (Detail)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Weighted average discount rate	5.10%	5.30%	2.70%
Weighted average accretion rate	4.80%	4.80%	4.90%
Weighted average duration (in years)	18 years	17 years	22 years
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Weighted average discount rate	5.10%	4.70%	2.40%
Weighted average accretion rate	3.30%	3.40%	3.40%
Weighted average duration (in years)	13 years	14 years	15 years