Loans - Loans by Class Modified as Troubled Debt Restructurings (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($) Loans	Dec. 31, 2015 USD ($) Loans	Dec. 31, 2014 USD ($) Loans
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	15	16
Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	7	8
Commercial Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	8	8
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	0	0
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	0	0
Credit Cards [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	0	0
Trouble Debt Restructuring [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	1	1	4
Pre-Modification Outstanding Recorded Investment \| $	$ 109	$ 1,327	$ 7,194
Post-Modification Outstanding Recorded Investment \| $	$ 109	$ 1,327	$ 7,194
Trouble Debt Restructuring [Member] \| Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	1	1	1
Pre-Modification Outstanding Recorded Investment \| $	$ 109	$ 1,327	$ 2,315
Post-Modification Outstanding Recorded Investment \| $	$ 109	$ 1,327	$ 2,315
Trouble Debt Restructuring [Member] \| Commercial Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	0	0	3
Pre-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 4,879
Post-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 4,879
Trouble Debt Restructuring [Member] \| Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	0	0	0
Pre-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 0
Trouble Debt Restructuring [Member] \| Consumer [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	0	0	0
Pre-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 0
Trouble Debt Restructuring [Member] \| Credit Cards [Member]
Financing Receivable, Impaired [Line Items]
Number of Loans \| Loans	0	0	0
Pre-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 0
Post-Modification Outstanding Recorded Investment \| $	$ 0	$ 0	$ 0

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953676-111524

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

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