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Loans (Troubled Debt Restructurings) (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | $ 13,426 | $ 15,911 | $ 60,510
Balance at Year-end | 11,674 | 0 | 58,484
Commercial Portfolio Segment [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 3,845 | 2,203 | 4,026
Balance at Year-end | 2,161 | 0 | 3,766
Commercial and Industrial Total Energy Loans [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 0 | 13,708 | 56,096
Balance at Year-end | 0 | 0 | 54,330
Commercial Real Estate, Buildings, Land and Other [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 9,457 | 0 | 0
Balance at Year-end | 9,393 | 0 | 0
Construction Loans [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 0 | 0 | 388
Balance at Year-end | 0 | 0 | 388
Total consumer real estate loans [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 124 | 0 | 0
Balance at Year-end | $ 120 | $ 0 | $ 0

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- Definition Amount, after troubled debt restructuring, of modified financing receivable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524 + Details
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