Loans and asset quality - Loan Distribution and Industry Concentrations (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 88,741	$ 80,615
Unearned income on lease financings	72	86
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,802	1,748
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	6,719	6,710
Financial institutions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	15,297	13,309
Wealth management loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	9,745	9,520
Wealth management mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	8,721	8,586
Other residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	1,665	1,820
Capital call financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	5,532	5,336
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,934	4,533
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	4,128	2,800
Margin loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 30,198	$ 26,253