Loans and the Allowance for Credit Losses - Loans Identified as TDRs (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) Contract	Dec. 31, 2019 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	8	11
Pre-Modification Outstanding Recorded Investment	$ 460	$ 1,093
Post-Modification Outstanding Recorded Investment	$ 443	$ 1,037
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract		2
Pre-Modification Outstanding Recorded Investment		$ 57
Post-Modification Outstanding Recorded Investment		$ 48
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract		1
Pre-Modification Outstanding Recorded Investment		$ 610
Post-Modification Outstanding Recorded Investment		$ 603
Commercial Real Estate [Member] \| Commercial Real Estate - Improved Property [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract		1
Pre-Modification Outstanding Recorded Investment		$ 610
Post-Modification Outstanding Recorded Investment		$ 603
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	3	4
Pre-Modification Outstanding Recorded Investment	$ 360	$ 194
Post-Modification Outstanding Recorded Investment	$ 350	$ 177
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	4	2
Pre-Modification Outstanding Recorded Investment	$ 93	$ 187
Post-Modification Outstanding Recorded Investment	$ 86	$ 181
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	1	2
Pre-Modification Outstanding Recorded Investment	$ 7	$ 45
Post-Modification Outstanding Recorded Investment	$ 7	$ 28

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Number of financing receivables that have been modified by troubled debt restructurings.

+ 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

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Amount, after troubled debt restructuring, of modified financing receivable.

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Amount, before troubled debt restructuring, of financing receivable to be modified.

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