Loans and asset quality - Credit Risk Indicators Narrative (Details) - USD ($)	6 Months Ended	12 Months Ended
Jun. 30, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of exposure to investment grade securities	96.00%
Percentage of financial institution exposure secured	65.00%
Percent of financial institution exposure expiring within one year	84.00%
Loans	$ 69,347,000,000	$ 67,787,000,000
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)	61.00%
Loans	$ 8,777,000,000	8,200,000,000
Wealth management mortgages \| California \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	22.00%
Wealth management mortgages \| New York \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	15.00%
Wealth management mortgages \| Florida \| Geographic Concentration Risk \| Revenue Benchmark
Accounts, Notes, Loans and Financing Receivable [Line Items]
Geographic concentrations (percent)	10.00%
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)	45.00%
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	$ 369,000,000	299,000,000
Fixed-Rate Jumbo Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan to value ratio at origination (percent)	69.00%
Loans	$ 96,000,000
Margin loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	19,316,000,000	22,487,000,000
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	3,800,000,000
Overdrafts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 3,793,000,000	$ 3,060,000,000
Overdraft repayment period	2 days	2 days

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Percentage of Exposure to Investment Grade Securities

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