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Long-duration insurance contracts - Summary of life, annuity and health insurance benefits liabilities (Detail) - USD ($) $ in Millions | Mar. 31, 2025 | Mar. 31, 2024
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Liabilities for Guarantees on Long-Duration Contracts [Line Items] |  |
Life, annuity and health insurance benefits | $ 17,734 | $ 17,987
Periodic Payment Annuity [Member] |  |
Liabilities for Guarantees on Long-Duration Contracts [Line Items] |  |
Life, annuity and health insurance benefits | 10,376 | 10,749
Life and Health [Member] |  |
Liabilities for Guarantees on Long-Duration Contracts [Line Items] |  |
Life, annuity and health insurance benefits | 4,485 | 4,259
Other [Member] |  |
Liabilities for Guarantees on Long-Duration Contracts [Line Items] |  |
Life, annuity and health insurance benefits | $ 2,873 | $ 2,979

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