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Loans (Allowance for Credit Losses By Loan Class in Accordance With Methodology Used Prior to CECL) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | $ 132,167
Commercial Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 51,593
Commercial and Industrial Total Energy Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 37,382
Commercial Real Estate Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 31,037
Total consumer real estate loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 4,113
Consumer Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 8,042
Historical Valuation Allowances [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 69,087
Historical Valuation Allowances [Member] | Commercial Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 29,015
Historical Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 7,873
Historical Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 21,947
Historical Valuation Allowances [Member] | Total consumer real estate loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 2,690
Historical Valuation Allowances [Member] | Consumer Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 7,562
Specific Valuation Allowances [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses | $ 15,279 | 28,483
Specific Valuation Allowances [Member] | Commercial Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses | 5,321 | 7,849
Specific Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses | 9,427 | 20,246
Specific Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 383
Specific Valuation Allowances [Member] | Total consumer real estate loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses | 0 | 0
Specific Valuation Allowances [Member] | Consumer Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses | $ 18 | 5
General Valuation Allowances [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 19,732
General Valuation Allowances [Member] | Commercial Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 9,840
General Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 5,196
General Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 4,201
General Valuation Allowances [Member] | Total consumer real estate loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 904
General Valuation Allowances [Member] | Consumer Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | (409)
Macroeconomic Valuation Allowances [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 14,865
Macroeconomic Valuation Allowances [Member] | Commercial Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 4,889
Macroeconomic Valuation Allowances [Member] | Commercial and Industrial Total Energy Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 4,067
Macroeconomic Valuation Allowances [Member] | Commercial Real Estate Portfolio Segment [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 4,506
Macroeconomic Valuation Allowances [Member] | Total consumer real estate loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | 519
Macroeconomic Valuation Allowances [Member] | Consumer Loan [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Portion of allowance for loan losses |  | $ 884

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