Loans and asset quality - Allowance for Credit Losses Activity (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 322	$ 370	$ 319	$ 366
Charge-offs	0	(10)	0	(20)
Recoveries	1	5	12	6
Net (charge-offs) recoveries	1	(5)	12	(14)
Provision	(11)	(20)	(19)	(7)
Ending balance	312	345	312	345
Allowance for loan losses	222	275	222	275	$ 245
Allowance for lending-related commitments	90	70	90	70	$ 74
Individually evaluated for impairment:
Loan balance	59	199	59	199
Allowance for loan losses	6	52	6	52
Provision (benefit) for other credit losses	3	3	4	8
Fair value of collateral	75	169	75	169
Asset Pledged as Collateral
Individually evaluated for impairment:
Loan balance	59	199	59	199
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	12	15	10	20
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0
Provision	3	(2)	5	(7)
Ending balance	15	13	15	13
Allowance for loan losses	3	2	3	2
Allowance for lending-related commitments	12	11	12	11
Individually evaluated for impairment:
Loan balance	0	0	0	0
Allowance for loan losses	0	0	0	0
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	248	326	262	315
Charge-offs	0	(10)	0	(20)
Recoveries	0	5	11	5
Net (charge-offs) recoveries	0	(5)	11	(15)
Provision	(26)	(30)	(51)	(9)
Ending balance	222	291	222	291
Allowance for loan losses	170	245	170	245
Allowance for lending-related commitments	52	46	52	46
Individually evaluated for impairment:
Loan balance	50	198	50	198
Allowance for loan losses	6	52	6	52
Financial institutions
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	32	16	25	19
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0
Provision	10	9	17	6
Ending balance	42	25	42	25
Allowance for loan losses	22	13	22	13
Allowance for lending-related commitments	20	12	20	12
Individually evaluated for impairment:
Loan balance	0	0	0	0
Allowance for loan losses	0	0	0	0
Wealth management loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	8	1	5	1
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0
Provision	0	0	3	0
Ending balance	8	1	8	1
Allowance for loan losses	6	1	6	1
Allowance for lending-related commitments	2	0	2	0
Individually evaluated for impairment:
Loan balance	0	0	0	0
Allowance for loan losses	0	0	0	0
Wealth management mortgages
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	8	6	7	6
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0
Provision	0	0	1	0
Ending balance	8	6	8	6
Allowance for loan losses	7	6	7	6
Allowance for lending-related commitments	1	0	1	0
Individually evaluated for impairment:
Loan balance	7	1	7	1
Allowance for loan losses	0	0	0	0
Other residential mortgages
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	4	2	2	2
Charge-offs	0	0	0	0
Recoveries	1	0	1	1
Net (charge-offs) recoveries	1	0	1	1
Provision	0	0	2	(1)
Ending balance	5	2	5	2
Allowance for loan losses	5	2	5	2
Allowance for lending-related commitments	0	0	0	0
Individually evaluated for impairment:
Loan balance	2	0	2	0
Allowance for loan losses	0	0	0	0
Capital call financing
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	10	4	8	3
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0
Provision	2	3	4	4
Ending balance	12	7	12	7
Allowance for loan losses	9	6	9	6
Allowance for lending-related commitments	3	1	3	1
Individually evaluated for impairment:
Loan balance	0	0	0	0
Allowance for loan losses	$ 0	$ 0	$ 0	$ 0

Financing Receivable, Allowance for Credit Loss and Off Balance Sheet Credit Loss, Liability

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Financing Receivable, Allowance for Credit Loss and Off Balance Sheet Credit Loss, Liability, Expense (Reversal)

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Financing Receivable, Allowance for Credit Loss and Off Balance Sheet Credit Loss, Liability, Recovery

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Financing Receivable, Allowance for Credit Loss and Off Balance Sheet Credit Loss, Liability, Writeoff

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Financing Receivable, Allowance for Credit Loss and Off Balance Sheet Credit Loss, Liability, Writeoff, after Recovery

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Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

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Amount of allowance for credit loss on financing receivable evaluated on individual basis. Excludes financing receivable evaluated on collective basis.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of financing receivable individually evaluated for credit loss. Excludes financing receivable collectively evaluated for credit loss.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of expense related to credit loss from transactions other than loan and lease transactions.

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- Definition

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

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