Loans - Summary of Receivables which were Modified and as Result Became Classified as TDR Loans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	$ 65	$ 224	$ 12
Commercial loans:
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	26	139	0
Commercial loans: | Business and corporate banking
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	11	95	0
Commercial loans: | Global banking
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	15	44	0
Consumer loans:
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	39	85	12
Consumer loans: | Residential mortgages
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	36	78	8
Consumer loans: | Home equity mortgages
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	1	3	1
Consumer loans: | Credit cards
Financing Receivable, Impaired [Line Items]
Loans which were modified and as a result became classified as TDR Loans	$ 2	$ 4	$ 3