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Derivative Financial Instruments (Schedule of Amounts Related to Non-Hedging Interest Rate and Commodity Derivatives) (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Interest Rate Contract [Member] | Other Non-Interest Income [Member] |  |  |
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items] |  |  |
Amount included in income or expense | $ 3,123 | $ 2,883 | $ 2,580
Interest Rate Contract [Member] | Other Non-Interest Expense [Member] |  |  |
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items] |  |  |
Amount included in income or expense | 1 | 0 | (43)
Commodity Contract [Member] | Other Non-Interest Income [Member] |  |  |
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items] |  |  |
Amount included in income or expense | 440 | 421 | 208
Foreign Exchange Contract [Member] | Other Non-Interest Income [Member] |  |  |
Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items] |  |  |
Amount included in income or expense | $ 300 | $ 30 | $ 78

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- Definition Other Non Interest Income Non Hedging Interest Rate Derivatives [Line Items] + References No definition available. + 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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