Loans and the Allowance for Credit Losses - Loans Identified as TDRs (Detail) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($) Contract	Jun. 30, 2018 USD ($) Contract	Jun. 30, 2019 USD ($) Contract	Jun. 30, 2018 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	2	4	9	11
Pre-Modification Outstanding Recorded Investment	$ 243	$ 68	$ 639	$ 278
Post-Modification Outstanding Recorded Investment	$ 196	$ 65	$ 581	$ 252
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	1	1	1	1
Pre-Modification Outstanding Recorded Investment	$ 44	$ 9	$ 44	$ 10
Post-Modification Outstanding Recorded Investment	$ 40	$ 9	$ 40	$ 9
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract			4	5
Pre-Modification Outstanding Recorded Investment			$ 194	$ 203
Post-Modification Outstanding Recorded Investment			$ 188	$ 185
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract		2	1	4
Pre-Modification Outstanding Recorded Investment		$ 39	$ 15	$ 45
Post-Modification Outstanding Recorded Investment		$ 36	$ 13	$ 38
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of Modifications \| Contract	1	1	3	1
Pre-Modification Outstanding Recorded Investment	$ 199	$ 20	$ 386	$ 20
Post-Modification Outstanding Recorded Investment	$ 156	$ 20	$ 340	$ 20

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=118936363&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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