Securities - Components of Available for Sale Portfolio (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	$ 255,676	$ 271,705
Available-for-sale securities, Gross unrealized gains	100	1,016
Available-for-sale securities, Gross unrealized losses	(8,146)	(2,160)
Available-for-sale securities, Total fair value	247,630	270,561
U.S. Treasury and Government Sponsored Entities' Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	124,639	124,982
Available-for-sale securities, Gross unrealized gains		19
Available-for-sale securities, Gross unrealized losses	(4,201)	(1,184)
Available-for-sale securities, Total fair value	120,438	123,817
States of the U.S. and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	48,414	58,806
Available-for-sale securities, Gross unrealized gains	65	955
Available-for-sale securities, Gross unrealized losses	(834)	(138)
Available-for-sale securities, Total fair value	47,645	59,623
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	489
Available-for-sale securities, Total fair value	489
Mortgage-Backed GSE Securities: Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Total amortized cost	82,134	87,917
Available-for-sale securities, Gross unrealized gains	35	42
Available-for-sale securities, Gross unrealized losses	(3,111)	(838)
Available-for-sale securities, Total fair value	$ 79,058	$ 87,121

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)
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-Publisher FASB
-Name Accounting Standards Codification
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-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
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-Name Accounting Standards Codification
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-Section 45
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-Publisher FASB
-Name Accounting Standards Codification
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