Commitments, Credit Risk and Contingencies - Summary of Off-Balance Sheet Credit Risk Information (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Standby letters of credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Extended credit and standby letters of credit	$ 158	$ 150
Commitments to extend credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Extended credit and standby letters of credit	$ 9,285	$ 8,089

The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

Name:	us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant