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Loans (Troubled Debt Restructurings) (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Financing Receivable, Modifications [Line Items] |  |  |
Balance at Restructure | $ 91,418 | $ 709 | $ 8,916
Balance at Year-end | 44,863 | 536 | 8,339
Commercial Portfolio Segment [Member] |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Balance at Restructure | 2,148 | 709 | 5,795
Balance at Year-end | 1,022 | 536 | 5,391
Commercial and Industrial, Energy [Member] |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Balance at Restructure | 87,572 | 0 | 0
Balance at Year-end | 43,841 | 0 | 0
Commercial Real Estate, Buildings, Land and Other [Member] |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Balance at Restructure | 1,455 | 0 | 3,121
Balance at Year-end | 0 | 0 | 2,948
Construction Loans [Member] |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Balance at Restructure | 243 | 0 | 0
Balance at Year-end | $ 0 | $ 0 | $ 0

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- Definition Post-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953676-111524 + Details
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