Loans - Summary of TDRs (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	$ 157	$ 200
Residential mortgage loan TDR carried at lower of amortized cost or fair value less cost to sell	95	104
Non Accrual loans included in TDR loan	67	115
Commercial loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	23	63
Additional commitments to lend to commercial borrowers with modified TDRs	14	13
Commercial loans: | Business and corporate banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	15	38
Commercial loans: | Global banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	8	25
Consumer loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	134	137
Consumer loans: | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	122	125
Consumer loans: | Home equity mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	9	9
Consumer loans: | Credit cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR Loans	$ 3	$ 3