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Loans and Related Allowance for Loan and Lease Losses - Classes of the Loan Portfolio Summarized by Nonaccrual Loans and Still Accruing (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans, nonacrrual status	$ 6,490	$ 7,545	$ 7,347
Loans, 90+ days past due and accruing	0	2	165
Commercial And Industrial [Member]
Loans, nonacrrual status	920	1,450	365
Loans, 90+ days past due and accruing	0	0	0
Real Estate Construction Porfolio Segment [Member]
Loans, nonacrrual status	17	130	587
Loans, 90+ days past due and accruing	0	0	0
Real Estate Mortgage Portfolio Segment [Member] | Residential Loan [Member]
Loans, nonacrrual status	3,822	4,122	5,310
Loans, 90+ days past due and accruing	0	0	165
Real Estate Mortgage Portfolio Segment [Member] | Commercial Loans [Member]
Loans, nonacrrual status	1,730	1,842	1,083
Loans, 90+ days past due and accruing	0	0	0
Consumer Portfolio Segment [Member]
Loans, nonacrrual status	0	1	2
Loans, 90+ days past due and accruing	$ 0	$ 2	$ 0

X

- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ 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 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Recorded investment in financing receivables that are on nonaccrual status as of 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 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524

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- Details

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- Details

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