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Significant Accounting Policies - Impact of new financial accounting standards (Details) - USD ($) $ in Thousands | Mar. 31, 2020 | Jan. 01, 2020 | Dec. 31, 2019
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Recently Issued Accounting Standards |  |  |
Change in Accounting Principle, Accounting Standards Update, Adopted [true false] |  | true |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  | $ (15,922)
Right of use asset | $ 9,074 |  | 9,490
Lease liability | $ 9,150 |  | $ 9,552
Allowance for credit losses on loans |  |  |
Recently Issued Accounting Standards |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  | $ 12,000 |
Post ASC 326 |  |  |
Recently Issued Accounting Standards |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  | (15,900) |
Post ASC 326 | Reserve for off-balance-sheet credit exposures |  |  |
Recently Issued Accounting Standards |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  | $ 3,900 |

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