Bank Premises and Equipment - Additional Information (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2022 USD ($) branch	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) branch	Jun. 30, 2021 USD ($)
Property, Plant and Equipment [Line Items]
Impairment losses on bank premises \| $	$ 1	$ 2	$ 1	$ 4
Closed in 2022
Property, Plant and Equipment [Line Items]
Number of branches held for sale \| branch	41		41

The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=126905981&loc=d3e2611-110228

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