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Summary of Significant Accounting Policies - Impact of ASU 2016-13 (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Jan. 01, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | --- | ---
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | $ 7,225,860 |  | $ 7,137,152 |
Allowance for credit losses on loans | (117,612) | $ (62,224) | (62,224) | $ (60,996)
Total loans | 7,108,248 | 7,074,928 | 7,074,928 |
Net deferred tax asset | 18,193 | 13,206 | 13,206 |
Allowance for credit losses on unfunded loan commitments | 4,467 | 3,113 | 3,112 | 2,139
Retained earnings | 710,061 | 761,083 | 761,083 |
As Reported Under ASU 2016-13 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Allowance for credit losses on loans |  | (89,577) |  |
Total loans |  | 7,047,575 |  |
Net deferred tax asset |  | 19,317 |  |
Allowance for credit losses on unfunded loan commitments |  | 4,462 | 4,461 | 2,139
Retained earnings |  | 738,493 |  |
Impact of ASU 2016-13 Adoption |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Allowance for credit losses on loans |  | (27,353) | (27,346) |
Total loans |  | (27,353) |  |
Net deferred tax asset |  | 6,111 |  |
Allowance for credit losses on unfunded loan commitments |  | 1,349 | 1,349 | 0
Retained earnings |  | (22,590) |  |
Commercial |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 5,977,643 |  | 5,756,971 |
Commercial | Commercial real estate |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 2,791,947 | 3,416,518 | 3,059,592 |
Allowance for credit losses on loans | (65,656) |  | (30,577) | (33,707)
Commercial | Commercial real estate | As Reported Under ASU 2016-13 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | 2,946,319 |  |
Commercial | Commercial real estate | Impact of ASU 2016-13 Adoption |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | (470,199) |  |
Allowance for credit losses on loans |  |  | (4,810) |
Commercial | Commercial and industrial |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 1,559,552 | 1,720,833 | 1,480,529 |
Allowance for credit losses on loans | (16,100) |  | (15,681) | (11,596)
Commercial | Commercial and industrial | As Reported Under ASU 2016-13 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | 1,458,541 |  |
Commercial | Commercial and industrial | Impact of ASU 2016-13 Adoption |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | (262,292) |  |
Allowance for credit losses on loans |  | (9,900) | (7,853) |
Commercial | Commercial construction |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 466,077 | 375,445 | 370,060 |
Allowance for credit losses on loans | (7,239) |  | (7,900) | (7,983)
Commercial | Commercial construction | As Reported Under ASU 2016-13 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | 345,263 |  |
Commercial | Commercial construction | Impact of ASU 2016-13 Adoption |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | (30,182) |  |
Allowance for credit losses on loans |  |  | 3,376 |
Commercial | Business banking |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 1,160,067 | 0 | 846,790 |
Allowance for credit losses on loans | (15,917) |  | 0 |
Commercial | Business banking | As Reported Under ASU 2016-13 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | 1,092,908 |  |
Commercial | Business banking | Impact of ASU 2016-13 Adoption |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | 1,092,908 |  |
Allowance for credit losses on loans |  |  | (12,898) |
Consumer |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 1,248,217 |  | 1,380,181 |
Consumer | Commercial construction |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  |  | 8,390 |
Consumer | Consumer real estate |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 1,167,332 | 1,545,323 | 1,295,207 |
Allowance for credit losses on loans | (10,014) |  | (6,337) | (6,187)
Consumer | Consumer real estate | As Reported Under ASU 2016-13 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | 1,235,352 |  |
Consumer | Consumer real estate | Impact of ASU 2016-13 Adoption |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | (309,971) |  |
Allowance for credit losses on loans |  |  | (4,525) |
Consumer | Other consumer |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance | 80,885 | 79,033 | 84,974 |
Allowance for credit losses on loans | $ (2,686) |  | (1,729) | $ (1,523)
Consumer | Other consumer | As Reported Under ASU 2016-13 |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | 58,769 |  |
Consumer | Other consumer | Impact of ASU 2016-13 Adoption |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Loans held for investment, outstanding balance |  | $ (20,264) |  |
Allowance for credit losses on loans |  |  | $ (636) |

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