Loans and Related Allowance for Loan and Lease Losses - Past Due Financing Receivables (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans, current balance	$ 583,017	$ 529,146	$ 465,164
Loans, past due	3,312	4,564	5,420
Total loans	586,329	533,710	470,584
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, past due	1,308	1,912	2,471
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, past due	639	121	434
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, past due	1,365	2,531	2,515
Commercial And Industrial [Member]
Loans, current balance	58,889	41,544	34,480
Loans, past due	487	992	448
Total loans	59,376	42,536	34,928
Commercial And Industrial [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, past due	59	225	349
Commercial And Industrial [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, past due	92	26	68
Commercial And Industrial [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, past due	336	741	31
Real Estate Construction Porfolio Segment [Member]
Loans, current balance	17,633	22,137	30,296
Loans, past due	0
Total loans	17,633	22,137	30,296
Real Estate Construction Porfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, past due	0	0
Real Estate Construction Porfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, past due	0	0
Real Estate Construction Porfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, past due	0	0
Real Estate Mortgage Portfolio Segment [Member] \| Residential Loan [Member]
Loans, current balance	257,068	229,725	205,753
Loans, past due	1,884	2,753	4,343
Total loans	258,952	232,478	210,096
Real Estate Mortgage Portfolio Segment [Member] \| Commercial Loans [Member]
Loans, current balance	244,771	230,903	190,088
Loans, past due	865	798	597
Total loans	245,636	231,701	190,685
Real Estate Mortgage Portfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member] \| Residential Loan [Member]
Loans, past due	1,052	1,482	2,065
Real Estate Mortgage Portfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member] \| Commercial Loans [Member]
Loans, past due	121	189	30
Real Estate Mortgage Portfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member] \| Residential Loan [Member]
Loans, past due	547	92	363
Real Estate Mortgage Portfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member] \| Commercial Loans [Member]
Loans, past due
Real Estate Mortgage Portfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Residential Loan [Member]
Loans, past due	285	1,179	1,915
Real Estate Mortgage Portfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member] \| Commercial Loans [Member]
Loans, past due	744	609	567
Consumer Portfolio Segment [Member]
Loans, current balance	4,656	4,837	4,547
Loans, past due	76	21	32
Total loans	4,732	4,858	4,579
Consumer Portfolio Segment [Member] \| Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, past due	$ 76	16	27
Consumer Portfolio Segment [Member] \| Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, past due		3	3
Consumer Portfolio Segment [Member] \| Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, past due		$ 2	$ 2

Financing receivables that are current.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

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- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524

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