Loans and asset quality - Credit Risk Indicators Narrative (Details) - USD ($)	6 Months Ended	12 Months Ended
Jun. 30, 2026	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of exposure to investment grade securities	96.00%
Percentage of financial institution exposure secured	59.00%
Percent of financial institution exposure expiring within one year	75.00%
Loans	$ 88,741,000,000	$ 80,615,000,000
Reverse repurchase agreements, allowance for credit loss	$ 0	0
Wealth management mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan to value ratio at origination (percent)	62.00%
Loans	$ 8,721,000,000	8,586,000,000
Wealth management mortgages \| California \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	20.00%
Wealth management mortgages \| New York \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	14.00%
Wealth management mortgages \| Florida \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	12.00%
Wealth management mortgages \| Massachusetts \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	8.00%
Wealth management mortgages \| Other \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	46.00%
Total wealth management loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of past due mortgages (less than)	1.00%
Other residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 1,665,000,000	1,820,000,000
Margin loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 30,198,000,000	26,253,000,000
Minimum collateral margin	1
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 4,100,000,000
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 4,128,000,000	$ 2,800,000,000
Overdraft repayment period	2 days	2 days

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Loan To Value Ratio

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Percentage Of Financial Institution Exposure To Investment Grade Securities

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

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Percentage of financing receivable balance that is past due.

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Amount of allowance for credit loss on security purchased under agreement to resell.

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