Loans and asset quality - Allowance for Credit Losses Activity (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 224	$ 241	$ 400	$ 241	$ 479
Charge-offs	0	0	(1)	0	(2)
Recoveries	1	1	3	2	5
Net (charge-offs) recoveries	1	1	2	2	3
Provision	18	(18)	(83)	0	(163)
Ending balance	243	224	319	243	319
Allowance for loan losses	181	171	269	181	269	$ 196
Allowance for lending-related commitments	62	53	50	62	50	45
Individually evaluated for impairment:
Loan balance	136	140	44	136	44
Allowance for loan losses	1	2	3	1	3
Provision for other credit losses	29	20	3	49	6
Fair value of collateral	179	183	50	179	50
Asset Pledged as Collateral
Individually evaluated for impairment:
Loan balance	136	140	44	136	44
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	12	12	11	12	16
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0	0
Provision	4	0	(3)	4	(8)
Ending balance	16	12	8	16	8
Allowance for loan losses	4	2	3	4	3
Allowance for lending-related commitments	12	10	5	12	5
Individually evaluated for impairment:
Loan balance	0	0	0	0	0
Allowance for loan losses	0	0	0	0	0
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	176	199	365	199	430
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0	0
Provision	8	(23)	(76)	(15)	(141)
Ending balance	184	176	289	184	289
Allowance for loan losses	147	142	248	147	248
Allowance for lending-related commitments	37	34	41	37	41
Individually evaluated for impairment:
Loan balance	121	121	26	121	26
Allowance for loan losses	1	1	3	1	3
Financial institutions
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	15	13	6	13	10
Charge-offs	0	0	0	0	0
Recoveries	0	0	2	0	2
Net (charge-offs) recoveries	0	0	2	0	2
Provision	6	2	(2)	8	(6)
Ending balance	21	15	6	21	6
Allowance for loan losses	10	7	3	10	3
Allowance for lending-related commitments	11	8	3	11	3
Individually evaluated for impairment:
Loan balance	0	0	0	0	0
Allowance for loan losses	0	0	0	0	0
Lease financings
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1	1	2	1	2
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0	0
Provision	0	0	0	0	0
Ending balance	1	1	2	1	2
Allowance for loan losses	1	1	2	1	2
Allowance for lending-related commitments	0	0	0	0	0
Individually evaluated for impairment:
Loan balance	0	0	0	0	0
Allowance for loan losses	0	0	0	0	0
Wealth management loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1	1	0	1	1
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0	0
Provision	0	0	1	0	0
Ending balance	1	1	1	1	1
Allowance for loan losses	1		1	1	1	1
Allowance for lending-related commitments	0		0	0	0	0
Individually evaluated for impairment:
Loan balance	0		0	0	0	0
Allowance for loan losses	0		0	0	0	$ 0
Wealth management mortgages
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	9	6	6	6	7
Charge-offs	0	0	0	0	(1)
Recoveries	0	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0	(1)
Provision	(2)	3	(2)	1	(2)
Ending balance	7	9	4	7	4
Allowance for loan losses	6	8	3	6	3
Allowance for lending-related commitments	1	1	1	1	1
Individually evaluated for impairment:
Loan balance	14	18	17	14	17
Allowance for loan losses	0	1	0	0	0
Other residential mortgages
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	7	7	9	7	13
Charge-offs	0	0	(1)	0	(1)
Recoveries	1	1	1	2	3
Net (charge-offs) recoveries	1	1	0	2	2
Provision	(1)	(1)	(1)	(2)	(7)
Ending balance	7	7	8	7	8
Allowance for loan losses	7	7	8	7	8
Allowance for lending-related commitments	0	0	0	0	0
Individually evaluated for impairment:
Loan balance	1	1	1	1	1
Allowance for loan losses	0	0	0	0	0
Capital call financing
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3	2	1	2	0
Charge-offs	0	0	0	0	0
Recoveries	0	0	0	0	0
Net (charge-offs) recoveries	0	0	0	0	0
Provision	3	1	0	4	1
Ending balance	6	3	1	6	1
Allowance for loan losses	5	3	1	5	1
Allowance for lending-related commitments	1	0	0	1	0
Individually evaluated for impairment:
Loan balance	0	0	0	0	0
Allowance for loan losses	$ 0	$ 0	$ 0	$ 0	$ 0