Loans and the Allowance for Credit Losses - Loans Identified as TDRs (Detail) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021 USD ($) Contract	Jun. 30, 2020 USD ($) Contract	Jun. 30, 2021 USD ($) Contract	Jun. 30, 2020 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	3	2	3	4
Pre-Modification Outstanding Recorded Investment	$ 2,097	$ 57	$ 2,120	$ 390
Post-Modification Outstanding Recorded Investment	$ 2,113	$ 56	$ 2,113	$ 384
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	2		2	2
Pre-Modification Outstanding Recorded Investment	$ 2,041		$ 2,064	$ 332
Post-Modification Outstanding Recorded Investment	$ 2,057		$ 2,057	$ 328
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	1	1	1	1
Pre-Modification Outstanding Recorded Investment	$ 56	$ 49	$ 56	$ 50
Post-Modification Outstanding Recorded Investment	$ 56	$ 48	$ 56	$ 48
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract		1		1
Pre-Modification Outstanding Recorded Investment		$ 8		$ 8
Post-Modification Outstanding Recorded Investment		$ 8		$ 8

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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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=123577603&loc=SL6953676-111524

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

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- Definition

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

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