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v3.20.4

Summary of Significant Accounting Policies (Impact of Adoption of New Accounting Standard Related to CECL) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Jan. 01, 2020 | Dec. 31, 2019 | Jan. 01, 2019 | Dec. 31, 2018 | Jan. 01, 2018 | Dec. 31, 2017
--- | --- | --- | --- | --- | --- | --- | ---
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss | $ 160 |  | $ 0 |  |  |  |
Financing Receivable, Allowance for Credit Loss | 263,177 |  | 132,167 |  |  |  |
Off-Balance Sheet, Credit Loss, Liability | 44,152 |  | 500 |  | $ 500 |  | $ 428
Cumulative effect of accounting change |  |  | (29,252) |  | (14,672) |  | (2,285)
Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | $ (29,300) | (29,252) | $ (14,700) | (14,672) | $ (2,300) | (2,285)
Commercial Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 73,843 |  | 51,593 |  | 48,580 |  | 59,614
Commercial Portfolio Segment [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | (16,798) |  |  |  |  |
Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 39,553 |  | 37,382 |  | 29,052 |  | 51,528
Commercial and Industrial Total Energy Loans [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | 8,258 |  |  |  |  |
Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 134,892 |  | 31,037 |  | 38,777 |  | 30,948
Commercial Real Estate Portfolio Segment [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | 10,680 |  |  |  |  |
Total consumer real estate loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 7,926 |  | 4,113 |  | 6,103 |  | 5,657
Total consumer real estate loans [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | (1,890) |  |  |  |  |
Consumer Loan [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 6,963 |  | 8,042 |  | 9,620 |  | 7,617
Consumer Loan [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | 1,776 |  |  |  |  |
Loans Receivable [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss | 263,177 |  | 132,167 |  | $ 132,132 |  | $ 155,364
Loans Receivable [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | 2,026 |  |  |  |  |
US Treasury [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | 0 |  |  |  |  |
Residential Mortgage Backed Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 |  | 0 |  |  |  |
Residential Mortgage Backed Securities [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | 0 |  |  |  |  |
States and Political Subdivisions [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 160 |  | 0 |  |  |  |
States and Political Subdivisions [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | (170) |  |  |  |  |
Other [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss | 0 |  | 0 |  |  |  |
Other [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | 0 |  |  |  |  |
Debt Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss | $ 160 |  | $ 0 |  |  |  |
Debt Securities [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | (170) |  |  |  |  |
Commitments to Extend Credit [Member] | Retained Earnings [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Cumulative effect of accounting change |  | (31,108) |  |  |  |  |
Pre-Adoption Allowance [Member] | Commercial Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 51,593 |  |  |  |  |
Pre-Adoption Allowance [Member] | Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 37,382 |  |  |  |  |
Pre-Adoption Allowance [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 31,037 |  |  |  |  |
Pre-Adoption Allowance [Member] | Total consumer real estate loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 4,113 |  |  |  |  |
Pre-Adoption Allowance [Member] | Consumer Loan [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 8,042 |  |  |  |  |
Pre-Adoption Allowance [Member] | Loans Receivable [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 132,167 |  |  |  |  |
Pre-Adoption Allowance [Member] | US Treasury [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Pre-Adoption Allowance [Member] | Residential Mortgage Backed Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Pre-Adoption Allowance [Member] | States and Political Subdivisions [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Pre-Adoption Allowance [Member] | Other [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Pre-Adoption Allowance [Member] | Debt Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Pre-Adoption Allowance [Member] | Commitments to Extend Credit [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability |  | 500 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Commercial Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 21,263 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | (10,453) |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | (13,519) |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Total consumer real estate loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 2,392 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Consumer Loan [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | (2,248) |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Loans Receivable [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | (2,565) |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | US Treasury [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Residential Mortgage Backed Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | States and Political Subdivisions [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 215 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Other [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Debt Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 215 |  |  |  |  |
Accounting Standards Update 2016-13 [Member] | Commitments to Extend Credit [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability |  | 39,377 |  |  |  |  |
Post-Adoption Allowance [Member] | Commercial Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 72,856 |  |  |  |  |
Post-Adoption Allowance [Member] | Commercial and Industrial Total Energy Loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 26,929 |  |  |  |  |
Post-Adoption Allowance [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 17,518 |  |  |  |  |
Post-Adoption Allowance [Member] | Total consumer real estate loans [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 6,505 |  |  |  |  |
Post-Adoption Allowance [Member] | Consumer Loan [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 5,794 |  |  |  |  |
Post-Adoption Allowance [Member] | Loans Receivable [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Loss |  | 129,602 |  |  |  |  |
Post-Adoption Allowance [Member] | US Treasury [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Post-Adoption Allowance [Member] | Residential Mortgage Backed Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Post-Adoption Allowance [Member] | States and Political Subdivisions [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 215 |  |  |  |  |
Post-Adoption Allowance [Member] | Other [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 0 |  |  |  |  |
Post-Adoption Allowance [Member] | Debt Securities [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss |  | 215 |  |  |  |  |
Post-Adoption Allowance [Member] | Commitments to Extend Credit [Member] |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability |  | $ 39,877 |  |  |  |  |

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