Loans and Allowance for Loan Losses - Summary of Subsequent Default (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021 USD ($) loan	Sep. 30, 2020 USD ($) loan	Sep. 30, 2021 USD ($) loan	Sep. 30, 2020 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	0	1	2	1
Recorded Investment \| $	$ 0	$ 40	$ 460	$ 40
Business banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	0	0	1	0
Recorded Investment \| $	$ 0	$ 0	$ 404	$ 0
Consumer home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts \| loan	0	1	1	1
Recorded Investment \| $	$ 0	$ 40	$ 56	$ 40

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No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

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- Definition

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

+ References

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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