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Goodwill - Narrative (Details) - USD ($) |  | 12 Months Ended |  |
--- | --- | --- | --- | ---
May 19, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Jul. 14, 2017 | Dec. 31, 2016
Business Acquisition [Line Items] |  |  |  |  |
Goodwill |  | $ 445,355,000 | $ 445,355,000 |  | $ 244,000,000
Measurement period adjustment |  |  | (469,000) |  |
Goodwill impairment loss |  | $ 0 | $ 0 |  |
IAB |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Goodwill |  |  |  | $ 153,636,000 |
Arlington Bank |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Goodwill | $ 47,719,000 |  |  |  |
Measurement period adjustment | $ 469,000 |  |  |  |

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