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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
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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

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