Fair Value of Assets and Liabilities - Additional information (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Securities available for sale	$ 239,922	$ 303,628
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Securities available for sale	1,790	$ 1,489
Significant Unobservable Inputs (Level 3) [Member] \| Trust Preferred Securities [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Securities available for sale	$ 1,800

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

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