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Derivatives - Additional Information (Detail) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2015 USD ($) Derivatives | Sep. 30, 2014 USD ($) | Sep. 30, 2015 USD ($) Derivatives | Sep. 30, 2014 USD ($) | Dec. 31, 2014 USD ($)
Risk participation Agreements [Line Items] |  |  |  |  |
HedgedItemsOfCashFlowHedge | $ 200,000 |  | $ 200,000 |  |
Derivative Instruments Designated As Hedging Instruments Interest Income | $ 565 | $ 29 | $ 1,503 | $ 29 |
Risk Participation Agreements Purchased [Domain] |  |  |  |  |
Risk participation Agreements [Line Items] |  |  |  |  |
Number of interest rate swaps | Derivatives | 15 |  | 15 |  |
Risk Participation Agreements Sold [Domain] |  |  |  |  |
Risk participation Agreements [Line Items] |  |  |  |  |
Number of interest rate swaps | Derivatives | 3 |  | 3 |  |
Designated as Hedging Instrument [Member] |  |  |  |  |
Risk participation Agreements [Line Items] |  |  |  |  |
Derivative, Notional Amount | $ 200,000 |  | $ 200,000 |  | $ 100,000
Three Year Maturity [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |
Risk participation Agreements [Line Items] |  |  |  |  |
Derivative, Notional Amount | 85,000 |  | 85,000 |  |
Four Year Maturity [Member] | Designated as Hedging Instrument [Member] |  |  |  |  |
Risk participation Agreements [Line Items] |  |  |  |  |
Derivative, Notional Amount | $ 115,000 |  | $ 115,000 |  |

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- Definition [Line Items] for Risk participation Agreements [Table] + References No definition available. + Details
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Number of credit risk derivative instruments held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5579245-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5580258-113959 + Details
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