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Loans - Troubled Debt Restructurings (Detail) - USD ($) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2016 | Mar. 31, 2015
Financing Receivable, Modifications [Line Items] |  |
Balance at time of restructuring | $ 62,808 | $ 709
Balance at period end | 61,347 | 613
Commercial Portfolio Segment [Member] |  |
Financing Receivable, Modifications [Line Items] |  |
Balance at time of restructuring | 19 | 709
Balance at period end | 17 | 613
Commercial and industrial, Energy [Member] |  |
Financing Receivable, Modifications [Line Items] |  |
Balance at time of restructuring | 62,546 | 0
Balance at period end | 61,095 | 0
Construction Loans [Member] |  |
Financing Receivable, Modifications [Line Items] |  |
Balance at time of restructuring | 243 | 0
Balance at period end | $ 235 | $ 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=49124121&loc=SL6953676-111524 + Details
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