Loans - Gross Charge-Offs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 5	$ 1	$ 16	$ 20
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			0
Three years prior to current year			0
Four years prior to current year			0
Prior			3
Revolving loans			3
Revolving Loans Converted to Term Loans			0
Total			6
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			0
Three years prior to current year			0
Four years prior to current year			0
Prior			3
Revolving loans			3
Revolving Loans Converted to Term Loans			0
Total	1	1	6	9
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			4
Total			10
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	0	0	1	1
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			4
Total	2	0	4	0
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	$ 0	$ 1	$ 0