Loans and the Allowance for Credit Losses - TDRs Defaulted Later Restructured (Detail) $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($) Default	Jun. 30, 2018 USD ($) Default
Financing Receivable, Modifications [Line Items]
Number of Defaults \| Default	2	3
Recorded Investment \| $	$ 110	$ 273
Commercial Real Estate - Improved Property [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults \| Default		1
Recorded Investment \| $		$ 145
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults \| Default		1
Recorded Investment \| $		$ 145
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults \| Default	1	1
Recorded Investment \| $	$ 97	$ 121
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults \| Default	1
Recorded Investment \| $	$ 13
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of Defaults \| Default		1
Recorded Investment \| $		$ 7

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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=118936363&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=118936363&loc=SL6953682-111524

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