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Amount of commitment to lend additional funds to debtor experiencing financial difficulty for which creditor has modified terms of financing receivable.

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Allowance for credit losses - Allowance for loan losses - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Modifications [Line Items]
Outstanding balance of loans modified for borrowers under financial difficulties that were subject to payment default	$ 7.0	$ 25.0
Reduction in interest rate
Financing Receivable, Modifications [Line Items]
Outstanding balance of loans modified for borrowers under financial difficulties that were subject to payment default		1.0
Extension of maturity date
Financing Receivable, Modifications [Line Items]
Outstanding balance of loans modified for borrowers under financial difficulties that were subject to payment default	6.0	22.0
Combination of reduction of interest rate and extension of maturity
Financing Receivable, Modifications [Line Items]
Outstanding balance of loans modified for borrowers under financial difficulties that were subject to payment default	1.0	2.0
Commercial
Financing Receivable, Modifications [Line Items]
Outstanding commitments to lend additional funds to debtors owing receivables whose terms have been modified in troubled debt restructurings	$ 65.0	$ 65.0	$ 17.0