Loans and asset quality - Credit Risk Profile by Origination (Details) $ in Millions	Jun. 30, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	$ 3,926
2019	4,407
2018	2,267
2017	2,951
2016	2,747
Prior to 2016	5,263
Amortized cost	29,628
Converted to term loans - Amortized cost	29
Total	51,218
Accrued interest receivable	77
Wealth management mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	491
2019	1,126
2018	719
2017	1,360
2016	1,736
Prior to 2016	2,976
Amortized cost	37
Converted to term loans - Amortized cost	0
Total	8,445
Wealth management loans and mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	525
2019	1,207
2018	731
2017	1,531
2016	1,792
Prior to 2016	3,096
Amortized cost	6,993
Converted to term loans - Amortized cost	0
Total	15,875
Accrued interest receivable	27
Other residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	450
Amortized cost	0
Converted to term loans - Amortized cost	0
Total	450
Accrued interest receivable	2
Other loans
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	0
Amortized cost	1,530
Converted to term loans - Amortized cost	0
Total	1,530
Accrued interest receivable	1
Margin loans
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	2,552
2019	1,000
2018	0
2017	0
2016	0
Prior to 2016	0
Amortized cost	9,357
Converted to term loans - Amortized cost	0
Total	12,909
Accrued interest receivable	11
Investment grade | Loans receivable
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	34
2019	81
2018	12
2017	171
2016	56
Prior to 2016	85
Amortized cost	6,877
Converted to term loans - Amortized cost	0
Total	7,316
Non-investment grade | Loans receivable
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	0
2019	0
2018	0
2017	0
2016	0
Prior to 2016	35
Amortized cost	79
Converted to term loans - Amortized cost	0
Total	114
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	147
2019	282
2018	118
2017	554
2016	60
Prior to 2016	0
Amortized cost	1,284
Converted to term loans - Amortized cost	0
Total	2,445
Accrued interest receivable	3
Commercial | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	107
2019	213
2018	106
2017	554
2016	57
Prior to 2016	0
Amortized cost	1,054
Converted to term loans - Amortized cost	0
Total	2,091
Commercial | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	40
2019	69
2018	12
2017	0
2016	3
Prior to 2016	0
Amortized cost	230
Converted to term loans - Amortized cost	0
Total	354
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	577
2019	1,622
2018	1,265
2017	729
2016	852
Prior to 2016	634
Amortized cost	520
Converted to term loans - Amortized cost	29
Total	6,228
Accrued interest receivable	8
Commercial real estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	500
2019	1,212
2018	806
2017	550
2016	431
Prior to 2016	422
Amortized cost	292
Converted to term loans - Amortized cost	0
Total	4,213
Commercial real estate | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	77
2019	410
2018	459
2017	179
2016	421
Prior to 2016	212
Amortized cost	228
Converted to term loans - Amortized cost	29
Total	2,015
Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	80
2019	276
2018	133
2017	125
2016	14
Prior to 2016	181
Amortized cost	9,944
Converted to term loans - Amortized cost	0
Total	10,753
Accrued interest receivable	25
Financial institutions | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	27
2019	247
2018	133
2017	125
2016	14
Prior to 2016	181
Amortized cost	7,934
Converted to term loans - Amortized cost	0
Total	8,661
Financial institutions | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	53
2019	29
2018	0
2017	0
2016	0
Prior to 2016	0
Amortized cost	2,010
Converted to term loans - Amortized cost	0
Total	2,092
Lease financings
Financing Receivable, Credit Quality Indicator [Line Items]
YTD20	45
2019	20
2018	20
2017	12
2016	29
Prior to 2016	902
Amortized cost	0
Converted to term loans - Amortized cost	0
Total	1,028
Accrued interest receivable	$ 0