Loans and asset quality - Loan Modifications (Details) $ in Millions	3 Months Ended
Jun. 30, 2026 USD ($) loan	Jun. 30, 2025 loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified after 12 months	$ 0
Commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans modified \| loan	2	0
Outstanding recorded investment Post- modification	$ 67
Commercial real estate \| Unfunded Loan Commitment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Outstanding recorded investment Post- modification	$ 1

Financing Receivable, Number Of Contracts Modified

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- Definition

Amortized cost excluding accrued interest, of financing receivable 12 months after modification for debtor experiencing financial difficulty.

+ References

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-Topic 310
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- Definition

Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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