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Short-term Borrowings - Interest Expense on Short-Term Borrowings (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Interest On Short Term Borrowings [Line Items] |  |  |
Total interest on short-term borrowings | $ 8,799 | $ 8,076 | $ 5,018
Federal funds purchased |  |  |
Interest On Short Term Borrowings [Line Items] |  |  |
Total interest on short-term borrowings | 77 | 41 | 54
Borrowings from FHLB |  |  |
Interest On Short Term Borrowings [Line Items] |  |  |
Total interest on short-term borrowings | 8,360 | 7,765 | 4,684
Securities sold under agreements to repurchase |  |  |
Interest On Short Term Borrowings [Line Items] |  |  |
Total interest on short-term borrowings | $ 362 | $ 270 | $ 280

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- Definition Interest On Short Term Borrowings [Line Items] + References No definition available. + Details
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- Definition The aggregate interest expense incurred on short-term borrowings including commercial paper and Federal funds purchased and securities sold under agreements to repurchase. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.7) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
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