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Loans - Gross Charge-Offs (Details) - USD ($) $ in Millions	12 Months Ended
Loans - Gross Charge-Offs (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 62	$ 26	$ 165
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0
One year prior to current year	0
Two years prior to current year	17
Three years prior to current year	0
Four years prior to current year	0
Prior	11
Revolving loans	20
Revolving Loans Converted to Term Loans	0
Total	48
Commercial loans \| Business and corporate banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0
One year prior to current year	0
Two years prior to current year	17
Three years prior to current year	0
Four years prior to current year	0
Prior	11
Revolving loans	20
Revolving Loans Converted to Term Loans	0
Total	48	9	29
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0
One year prior to current year	0
Two years prior to current year	0
Three years prior to current year	0
Four years prior to current year	0
Prior	6
Revolving loans	8
Total	14
Consumer loans \| Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0
One year prior to current year	0
Two years prior to current year	0
Three years prior to current year	0
Four years prior to current year	0
Prior	4
Revolving loans	0
Total	4
Consumer loans \| Home equity mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0
One year prior to current year	0
Two years prior to current year	0
Three years prior to current year	0
Four years prior to current year	0
Prior	1
Revolving loans	0
Total	1	1	5
Consumer loans \| Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0
One year prior to current year	0
Two years prior to current year	0
Three years prior to current year	0
Four years prior to current year	0
Prior	0
Revolving loans	8
Total	8	1	89
Consumer loans \| Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	0
One year prior to current year	0
Two years prior to current year	0
Three years prior to current year	0
Four years prior to current year	0
Prior	1
Revolving loans	0
Total	$ 1	$ 1	$ 10