Loans and asset quality - Allowance for Credit Losses Activity (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 216	$ 224	$ 252
Charge-offs	0	(1)	(11)
Recoveries	0	1	0
Net (charge-offs) recoveries	0	0	(11)
Provision	141	(8)	7
Ending balance	288	216	248
Individually evaluated for impairment:
Loan balance	18	15	100
Allowance for loan losses	0	0	10
Collectively evaluated for impairment:
Loan balance		54,938	53,387
Allowance for loan losses		122	136
Collateral dependent loans	18
Fair value of collateral	26
Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	122
Ending balance	140	122	146
Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	94
Ending balance	148	94	102
Domestic \| Overdrafts
Collectively evaluated for impairment:
Loans		524	654
Domestic \| Margin loans
Collectively evaluated for impairment:
Loans		11,907	12,107
Domestic \| Other
Collectively evaluated for impairment:
Loans		1,167	1,152
Foreign
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	24	28	32
Charge-offs	0	0	0
Recoveries	0	0	0
Net (charge-offs) recoveries	0	0	0
Provision	0	(4)	(3)
Ending balance	0	24	29
Individually evaluated for impairment:
Loan balance	0	0	0
Allowance for loan losses	0	0	0
Collectively evaluated for impairment:
Loan balance		12,405	11,324
Allowance for loan losses		15	19
Foreign \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	15
Ending balance	0	15	19
Foreign \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	9
Ending balance	0	9	10
Commercial \| Domestic
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	60	61	81
Charge-offs	0	0	(11)
Recoveries	0	0	0
Net (charge-offs) recoveries	0	0	(11)
Provision	9	(1)	12
Ending balance	26	60	82
Individually evaluated for impairment:
Loan balance	0	0	96
Allowance for loan losses	0	0	10
Collectively evaluated for impairment:
Loan balance		1,442	1,626
Allowance for loan losses		11	14
Commercial \| Domestic \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	11
Ending balance	13	11	24
Commercial \| Domestic \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	49
Ending balance	13	49	58
Commercial \| Foreign
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	10
Ending balance		10
Commercial real estate \| Domestic
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	76	77	75
Charge-offs	0	0	0
Recoveries	0	0	0
Net (charge-offs) recoveries	0	0	0
Provision	118	(1)	(1)
Ending balance	208	76	74
Individually evaluated for impairment:
Loan balance	0	0	0
Allowance for loan losses	0	0	0
Collectively evaluated for impairment:
Loan balance		5,575	4,921
Allowance for loan losses		57	56
Commercial real estate \| Domestic \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	57
Ending balance	83	57	56
Commercial real estate \| Domestic \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	19
Ending balance	125	19	18
Financial institutions \| Domestic
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	20	21	22
Charge-offs	0	0	0
Recoveries	0	0	0
Net (charge-offs) recoveries	0	0	0
Provision	4	(1)	1
Ending balance	18	20	23
Individually evaluated for impairment:
Loan balance	0	0	0
Allowance for loan losses	0	0	0
Collectively evaluated for impairment:
Loan balance		4,852	4,652
Allowance for loan losses		5	10
Financial institutions \| Domestic \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	5
Ending balance	10	5	10
Financial institutions \| Domestic \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	15
Ending balance	8	15	13
Financial institutions \| Foreign
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	10
Ending balance	12	10
Lease financings \| Domestic
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3	3	5
Charge-offs	0	0	0
Recoveries	0	0	0
Net (charge-offs) recoveries	0	0	0
Provision	10	0	(1)
Ending balance	13	3	4
Individually evaluated for impairment:
Loan balance	0	0	0
Allowance for loan losses	0	0	0
Collectively evaluated for impairment:
Loan balance		537	653
Allowance for loan losses		3	4
Lease financings \| Domestic \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3
Ending balance	13	3	4
Lease financings \| Domestic \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance	0	0	0
Lease financings \| Foreign
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	4
Ending balance		4
Wealth management loans and mortgages \| Domestic
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	20	20	21
Charge-offs	0	0	0
Recoveries	0	0	0
Net (charge-offs) recoveries	0	0	0
Provision	1	0	0
Ending balance	9	20	21
Individually evaluated for impairment:
Loan balance	18	15	4
Allowance for loan losses	0	0	0
Collectively evaluated for impairment:
Loan balance		16,035	15,724
Allowance for loan losses		18	18
Wealth management loans and mortgages \| Domestic \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	18
Ending balance	7	18	18
Wealth management loans and mortgages \| Domestic \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2
Ending balance	2	2	3
Other residential mortgages \| Domestic
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13	14	16
Charge-offs	0	(1)	0
Recoveries	0	1	0
Net (charge-offs) recoveries	0	0	0
Provision	(1)	(1)	(1)
Ending balance	14	13	15
Individually evaluated for impairment:
Loan balance	0	0	0
Allowance for loan losses	0	0	0
Collectively evaluated for impairment:
Loan balance		494	574
Allowance for loan losses		13	15
Other residential mortgages \| Domestic \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13
Ending balance	14	13	15
Other residential mortgages \| Domestic \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance	0	0	0
All other \| Domestic
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0	0	0
Charge-offs		0	0
Recoveries		0	0
Net (charge-offs) recoveries		0	0
Provision		0	0
Ending balance		0	0
Individually evaluated for impairment:
Loan balance		0	0
Allowance for loan losses		0	0
Collectively evaluated for impairment:
Loan balance		13,598	13,913
Allowance for loan losses		0	0
All other \| Domestic \| Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0	0
All other \| Domestic \| Lending-related commitments
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 0
Ending balance		$ 0	$ 0

Loans and Allowance for Loan Losses Collectively Evalueated for Impairment [Abstract]

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Amount, after recovery, of writeoff of financing receivable, charged against allowance for credit loss.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Reflects the aggregate value of loans, trade receivables, securities and financial instruments that serve as collateral for obligations arising from a transfer of financial assets recorded as a secured borrowing.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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Fair value of the securities pledged as collateral against securities loaned.

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