Loans - Loans Classified as TDR Loans (Detail) - Consumer loans: - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans which were classified as TDR loans during previous 12 months which became contractually delinquent	$ 0	$ 3
Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans which were classified as TDR loans during previous 12 months which became contractually delinquent	$ 0	$ 3

Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration