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Loans (Troubled Debt Restructurings) (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | $ 17,524 | $ 13,426 | $ 15,911
Balance at Year-end | 8,552 | 11,674 | 0
Commercial Portfolio Segment [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 3,661 | 3,845 | 2,203
Balance at Year-end | 192 | 2,161 | 0
Commercial and Industrial Total Energy Loans [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 2,432 | 0 | 13,708
Balance at Year-end | 2,421 | 0 | 0
Commercial Real Estate, Buildings, Land and Other [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 9,310 | 9,457 | 0
Balance at Year-end | 4,922 | 9,393 | 0
Construction Loans [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 1,017 | 0 | 0
Balance at Year-end | 1,017 | 0 | 0
Total consumer real estate loans [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 0 | 124 | 0
Balance at Year-end | 0 | 120 | 0
Consumer Loan [Member] |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Balance at Restructure | 1,104 | 0 | 0
Balance at Year-end | $ 0 | $ 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=121611835&loc=SL6953676-111524 + Details
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- Definition Amount, before troubled debt restructuring, of financing receivable to be modified. + 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=121611835&loc=SL6953676-111524 + Details
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