Variable interest entities and asset securitizations - Summary of Carrying Amount (Details) - Variable Interest Entity Primary Beneficiary - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Affordable Housing Projects
Variable Interest Entity [Line Items]
Investment in partnership carrying amount	$ 1,384	$ 1,340
Unfunded commitments includes carrying amount of its investments	467	410
Contingent commitments to provide additional capital contributions to partnerships	69	55
Renewable Energy
Variable Interest Entity [Line Items]
Investment in partnership carrying amount	135	80
Unfunded commitments includes carrying amount of its investments	46	31
Other Projects
Variable Interest Entity [Line Items]
Investment in partnership carrying amount	37	41
Unfunded commitments includes carrying amount of its investments	$ 0	$ 0