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Derivatives - Additional Information (Detail) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 USD ($) Derivative | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Derivative [Line Items] |  |  |
Number of participation agreements for interest rate swaps, participant | Derivative | 36 |  |
Number of participation agreements for interest rate swaps, lead bank | Derivative | 9 |  |
Derivative, Gain (Loss) on Derivative, Net | $ (473) | $ 219 | $ (274)
Interest Rate Swap [Member] | Cash Flow Hedging [Member] |  |  |
Derivative [Line Items] |  |  |
Number of interest rate swap contracts | Derivative | 3 |  |
Derivative, notional amount | $ 150,000 |  |
Collateral Already Posted, Aggregate Fair Value | 150,000 |  |
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, notional amount | 150,000 | 200,000 |
Interest Rate Swap [Member] | Interest Income [Member] | Designated as Hedging Instrument [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Gain (Loss) on Derivative, Net | 452 | 1,627 | 2,049
Interest Rate Swap [Member] | Other Income [Member] | Designated as Hedging Instrument [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Gain (Loss) on Derivative, Net | 119 | 70 | 64
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, notional amount | 10,077 | 4,749 |
Derivative, Underlying Asset Carrying Value | 10,000 | 4,700 |
Derivative Liability, Fair Value, Gross Asset | 10,100 | 4,700 |
Foreign Exchange Contract [Member] | Other Income [Member] | Designated as Hedging Instrument [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Gain (Loss) on Derivative, Net | 4 | (5) | 0
Forward Contracts [Member] | Designated as Hedging Instrument [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, notional amount | 17,000 | 0 |
Derivative, Underlying Asset Carrying Value | 14,300 |  |
Derivative Liability, Fair Value, Gross Asset | 14,700 |  |
Derivative Liability, Notional Amount | 13,800 |  |
Forward Contracts [Member] | Other Income [Member] | Designated as Hedging Instrument [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, Gain (Loss) on Derivative, Net | (19) | $ 0 | $ 0
Three Year [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, notional amount | $ 35,000 |  |
Derivative, Term of Contract | 3 years |  |
Four Year [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative, notional amount | $ 115,000 |  |
Derivative, Term of Contract | 4 years |  |

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- Definition Derivative, Underlying Asset Carrying Value + References No definition available. + Details
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- Definition Derivative, Underlying Asset Fair Value + References No definition available. + Details
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- Definition Number of Participation Agreements, Interest Rate Derivatives Held as a Participant + 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 The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624258-113959 + Details
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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + Details
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- Definition Nominal or face amount used to calculate payments on the derivative liability. + References Reference 1: 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=84234895&loc=SL5580258-113959 Reference 2: 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=84234895&loc=SL5579245-113959 + Details
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- Definition 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. + References No definition available. + Details
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- Definition The number of derivative instruments of a particular group held by the entity. + References Reference 1: 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=84234895&loc=SL5580258-113959 Reference 2: 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=84234895&loc=SL5579245-113959 + Details
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- Definition Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Number of interest rate derivative instruments held by the entity at the reporting date. + References Reference 1: 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=84234895&loc=SL5580258-113959 Reference 2: 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=84234895&loc=SL5579245-113959 + Details
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