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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 | 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] |  |  |
Undiscounted expected future benefits | $ 31,066 | $ 31,156 | $ 30,260
Life and Health [Member] |  |  |
Liability for Future Policy Benefit, Activity [Line Items] |  |  |
Undiscounted expected future gross premiums | 117,078 | 109,321 | 102,768
Discounted expected future gross premiums | 66,692 | 66,460 | 64,378
Undiscounted expected future benefits | $ 111,630 | $ 104,544 | $ 98,224

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