Allowance for Loan Losses - Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2016 USD ($) SecurityLoan	Sep. 30, 2015 USD ($) SecurityLoan	Sep. 30, 2016 USD ($) SecurityLoan	Sep. 30, 2015 USD ($) SecurityLoan
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number \| SecurityLoan	10	6	19	14
Pre-mod outstanding principal balance	$ 674	$ 1,565	$ 1,496	$ 2,424
Post-mod outstanding principal balance	682	1,564	1,542	2,431
Financial impact due to TDR taken as additional provision	$ 21	$ 5	$ 146	$ 262
Number that defaulted during the period \| SecurityLoan	2	2	3	5
Recorded investment of TDRs that defaulted during the period	$ 243	$ 368	$ 330	$ 550
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	$ 0	$ 0	$ 0	$ 0
Home Equity Lines of Credit [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number \| SecurityLoan	2	1	6	1
Pre-mod outstanding principal balance	$ 113	$ 142	$ 408	$ 141
Post-mod outstanding principal balance	$ 114	$ 141	411	$ 141
Financial impact due to TDR taken as additional provision			$ 73
Number that defaulted during the period \| SecurityLoan	1	1	1	2
Recorded investment of TDRs that defaulted during the period	$ 229	$ 125	$ 229	$ 172
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	$ 0	$ 0	$ 0	$ 0
C&I [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number \| SecurityLoan	3	2	4	5
Pre-mod outstanding principal balance	$ 65	$ 37	$ 77	$ 506
Post-mod outstanding principal balance	66	37	77	507
Financial impact due to TDR taken as additional provision	15	5	23	254
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	0	0	$ 0	$ 0
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number \| SecurityLoan			1	1
Pre-mod outstanding principal balance			$ 105	$ 69
Post-mod outstanding principal balance			105	74
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	0	0	0	0
Auto Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	0	0	0	0
Construction [Member] \| Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	0	0	0	0
Construction [Member] \| Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	$ 0	0	$ 0	$ 0
RE Mortgage [Member] \| Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number \| SecurityLoan	2		3	1
Pre-mod outstanding principal balance	$ 318		$ 650	$ 108
Post-mod outstanding principal balance	324		656	110
Financial impact due to TDR taken as additional provision	$ 6		$ 50	$ 8
Number that defaulted during the period \| SecurityLoan	1		2	1
Recorded investment of TDRs that defaulted during the period	$ 14		$ 101	$ 98
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	$ 0	$ 0	$ 0	$ 0
RE Mortgage [Member] \| Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number \| SecurityLoan	2	3	4	4
Pre-mod outstanding principal balance	$ 170	$ 1,386	$ 248	$ 1,511
Post-mod outstanding principal balance	170	$ 1,386	285	1,510
Financial impact due to TDR taken as additional provision				$ (5)
Number that defaulted during the period \| SecurityLoan		1		2
Recorded investment of TDRs that defaulted during the period		$ 243		$ 280
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	$ 0	0	$ 0	$ 0
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number \| SecurityLoan	1		1	2
Pre-mod outstanding principal balance	$ 8		$ 8	$ 89
Post-mod outstanding principal balance	8		8	89
Financial impact due to TDR taken as additional provision				5
Financial impact due to the default of previous TDR taken as charge-offs or additional provisions	$ 0	$ 0	$ 0	$ 0

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Financial Impact due to troubled debt restructure charge offs or additional provision.

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Financing receivable modification post modification recorded investment.

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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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Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524

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