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Allowance for Credit Losses - Collateral Dependent Loans by Class of Loan (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Jan. 01, 2020 | Dec. 31, 2019
--- | --- | --- | ---
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | $ 7,225,860 |  | $ 7,137,152
Real Estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 108,525 |  |
Blanket Lien |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 16,699 |  |
Investment/Cash |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Other |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 689 |  |
Commercial |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 5,977,643 |  | 5,756,971
Commercial | Commercial real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 2,791,947 | $ 3,416,518 | 3,059,592
Commercial | Commercial real estate | Real Estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 100,450 |  |
Commercial | Commercial real estate | Blanket Lien |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Commercial real estate | Investment/Cash |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Commercial real estate | Other |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Commercial and industrial |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 1,559,552 | 1,720,833 | 1,480,529
Commercial | Commercial and industrial | Real Estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 1,040 |  |
Commercial | Commercial and industrial | Blanket Lien |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 15,080 |  |
Commercial | Commercial and industrial | Investment/Cash |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Commercial and industrial | Other |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Other Consumer |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 466,077 | 375,445 | 370,060
Commercial | Other Consumer | Real Estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 3,552 |  |
Commercial | Other Consumer | Blanket Lien |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Other Consumer | Investment/Cash |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Other Consumer | Other |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Business banking |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 1,160,067 | 0 | 846,790
Commercial | Business banking | Real Estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 3,085 |  |
Commercial | Business banking | Blanket Lien |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 1,619 |  |
Commercial | Business banking | Investment/Cash |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Commercial | Business banking | Other |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 689 |  |
Consumer |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 1,248,217 |  | 1,380,181
Consumer | Other Consumer |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance |  |  | 8,390
Consumer | Consumer real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 1,167,332 | $ 1,545,323 | $ 1,295,207
Consumer | Consumer real estate | Real Estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 398 |  |
Consumer | Consumer real estate | Blanket Lien |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Consumer | Consumer real estate | Investment/Cash |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | 0 |  |
Consumer | Consumer real estate | Other |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Loans held for investment, outstanding balance | $ 0 |  |

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