Loans - Summary of the Financial Effect of Loan Payment Modifications (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Commercial loans \| Business and corporate banking
Financing Receivable, Modified [Line Items]
Weighted-Average Interest Rate Reduction	1.10%	0.00%	0.70%	0.30%
Weighted-Average Term Extension / Payment Deferral (in years)	2 years 8 months 12 days	1 year 7 months 6 days	1 year 4 months 24 days	1 year 8 months 12 days
Commercial loans \| Business and corporate banking \| Principal Forgiven
Financing Receivable, Modified [Line Items]
Principal Forgiven (in millions)	$ 0	$ 0	$ 0	$ 0
Commercial loans \| Real estate, including construction
Financing Receivable, Modified [Line Items]
Weighted-Average Interest Rate Reduction	0.00%	0.00%	0.00%	5.60%
Weighted-Average Term Extension / Payment Deferral (in years)	3 months 18 days	2 years 2 months 12 days	3 months 18 days	3 years 1 month 6 days
Commercial loans \| Real estate, including construction \| Principal Forgiven
Financing Receivable, Modified [Line Items]
Principal Forgiven (in millions)	$ 0	$ 0	$ 0	$ 0
Consumer loans \| Residential mortgages
Financing Receivable, Modified [Line Items]
Weighted-Average Interest Rate Reduction	0.00%		1.00%	0.50%
Weighted-Average Term Extension / Payment Deferral (in years)	6 months		8 months 12 days	7 months 6 days
Consumer loans \| Residential mortgages \| Principal Forgiven
Financing Receivable, Modified [Line Items]
Principal Forgiven (in millions)	$ 0		$ 0	$ 0

Amount of increase (decrease) in amortized cost excluding accrued interest, of financing receivable modified for debtor experiencing financial difficulty.

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