Loans and Allowance for Credit Losses - Troubled Debt Restructured Loans and Commitments (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 11,589	$ 13,579
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	81	223
Letter of Credit [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	60	60
Unused lines of Credit [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	21	163
Accrual Loans [Member] [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring	7,078	7,542
Non Accrual Loans [Member]
Financing Receivable, Troubled Debt Restructurings [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 4,511	$ 6,037

Financing Receivable, Troubled Debt Restructurings [Line Items] [Line Items]

No definition available.

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- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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- Definition

Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

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