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Long-duration insurance contracts - Summary of gross premiums earned and net interest expense (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
Annuities [Member] |  |
Liability for Future Policy Benefit, Activity [Line Items] |  |
Net Interest Expense | $ 550 | $ 537
Life and Health [Member] |  |
Liability for Future Policy Benefit, Activity [Line Items] |  |
Gross Premiums | 3,830 | 3,627
Net Interest Expense | $ 135 | $ 221

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