Loans and Related Allowance for Loan and Lease Losses - Major Classifications of Net Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable Gross	$ 586,329		$ 533,710			$ 470,584
Less: Allowance for loan and lease losses	6,334	$ 6,366	6,385	$ 6,320	$ 6,346	6,846	$ 7,046	$ 7,779
Net loans	579,995		527,325			463,738
Commercial And Industrial [Member]
Financing Receivable Gross	59,376		42,536			34,928
Less: Allowance for loan and lease losses	513	484	867	578	610	642	614	1,732
Real Estate Construction Porfolio Segment [Member]
Financing Receivable Gross	17,633		22,137			30,296
Less: Allowance for loan and lease losses	138	159	276	334	363	868	576	1,123
Real Estate Mortgage Portfolio Segment [Member] \| Residential Loan [Member]
Financing Receivable Gross	258,952		232,478			210,096
Less: Allowance for loan and lease losses	2,761	2,788	3,139	3,426	3,347	3,703	3,664	2,872
Real Estate Mortgage Portfolio Segment [Member] \| Commercial Loans [Member]
Financing Receivable Gross	245,636		231,701			190,685
Less: Allowance for loan and lease losses	2,895	2,909	2,078	1,939	1,978	1,576	2,170	1,991
Consumer Portfolio Segment [Member]
Financing Receivable Gross	4,732		4,858			4,579
Less: Allowance for loan and lease losses	$ 27	$ 26	$ 25	$ 43	$ 48	$ 57	$ 22	$ 61

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section 50
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SAB Topic 6.L.1)
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 310
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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-Section S99
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-Subparagraph (SX 210.9-03.7)
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