Loans - Summary of Receivables which were Modified and as Result Became Classified as TDR Loans (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	$ 107	$ 17	$ 118	$ 75
Commercial loans
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	99	0	101	41
Commercial loans | Business and corporate banking
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	99	0	101	26
Commercial loans | Global banking
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	0	0	0	15
Consumer loans
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	8	17	17	34
Consumer loans | Residential mortgages
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	5	16	12	32
Consumer loans | Home equity mortgages
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	2	1	2	1
Consumer loans | Credit cards
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	$ 1	$ 0	$ 3	$ 1