Securities - Components of Available for Sale Portfolio (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	$ 343,683	$ 361,503
Available-for-sale securities, Gross unrealized gains	10,787	406
Available-for-sale securities, Gross unrealized losses	(1)	(4,239)
Available-for-sale securities, Total fair value	354,469	357,670
U.S. Treasury and Government Sponsored Entities' Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	188,311	221,500
Available-for-sale securities, Gross unrealized gains	7,416	159
Available-for-sale securities, Gross unrealized losses		(3,009)
Available-for-sale securities, Total fair value	195,727	218,650
States of the U.S. and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	49,409	10,848
Available-for-sale securities, Gross unrealized gains	1,357	192
Available-for-sale securities, Gross unrealized losses	(1)
Available-for-sale securities, Total fair value	50,765	11,040
Mortgage-Backed GSE Securities: Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	105,963	129,155
Available-for-sale securities, Gross unrealized gains	2,014	55
Available-for-sale securities, Gross unrealized losses		(1,230)
Available-for-sale securities, Total fair value	$ 107,977	$ 127,980

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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Amount of debt securities categorized neither as held-to-maturity nor trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562

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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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