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Variable interest entities and asset securitizations - Summary of Carrying Amount (Details) - Variable Interest Entity Primary Beneficiary - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
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Affordable Housing Projects |  |
Variable Interest Entity [Line Items] |  |
Investment in partnership carrying amount | $ 1,598 | $ 1,384
Unfunded commitments includes carrying amount of its investments | 658 | 467
Contingent commitments to provide additional capital contributions to partnerships | 88 | 69
Renewable Energy |  |
Variable Interest Entity [Line Items] |  |
Investment in partnership carrying amount | 115 | 135
Unfunded commitments includes carrying amount of its investments | 65 | 46
Other Projects |  |
Variable Interest Entity [Line Items] |  |
Investment in partnership carrying amount | 34 | 37
Unfunded commitments includes carrying amount of its investments | $ 0 | $ 0

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