Loans - Summary of Past Due Status of Loans With Payment Modifications (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Financing Receivable, Past Due [Line Items]
Modified loans, past due	$ 628
30 - 89 Days
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
90+ Days
Financing Receivable, Past Due [Line Items]
Modified loans, past due	166
Current
Financing Receivable, Past Due [Line Items]
Modified loans, past due	462
Commercial loans
Financing Receivable, Past Due [Line Items]
Modified loans, past due	616
Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Modified loans, past due	168
Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	398
Loan with payment modification subsequently charged-off	32
Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	50
Commercial loans | 30 - 89 Days
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Commercial loans | 30 - 89 Days | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Commercial loans | 30 - 89 Days | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Commercial loans | 30 - 89 Days | Global banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Commercial loans | 90+ Days
Financing Receivable, Past Due [Line Items]
Modified loans, past due	166
Commercial loans | 90+ Days | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Modified loans, past due	166
Commercial loans | 90+ Days | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Commercial loans | 90+ Days | Global banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Commercial loans | Current
Financing Receivable, Past Due [Line Items]
Modified loans, past due	450
Commercial loans | Current | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Modified loans, past due	2
Commercial loans | Current | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	398
Commercial loans | Current | Global banking
Financing Receivable, Past Due [Line Items]
Modified loans, past due	50
Consumer loans
Financing Receivable, Past Due [Line Items]
Modified loans, past due	12
Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Modified loans, past due	12
Consumer loans | 30 - 89 Days
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Consumer loans | 30 - 89 Days | Residential mortgages
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Consumer loans | 90+ Days
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Consumer loans | 90+ Days | Residential mortgages
Financing Receivable, Past Due [Line Items]
Modified loans, past due	0
Consumer loans | Current
Financing Receivable, Past Due [Line Items]
Modified loans, past due	12
Consumer loans | Current | Residential mortgages
Financing Receivable, Past Due [Line Items]
Modified loans, past due	$ 12