| **Acquisitions - Pro Forma Financial Information (Details) - Arlington Bank and IAB - USD ($) $ / shares in Units, $ in Thousands** | 3 Months Ended | 9 Months Ended | 12 Months Ended |
|-------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|-----------------|
||
| **Business Acquisition [Line Items]**                                                                                               |           |           |            |
| Total revenue (net interest income plus other income)                                                                               | $ 96,178       | $ 281,392      | $ 353,732       |
| Net income                                                                                                                          | $ 19,603       | $ 70,651       | $ 95,288        |
| Basic (in dollars per share)                                                                                                        | $ 0.40         | $ 1.44         | $ 1.95          |
| Diluted (in dollars per share)                                                                                                      | $ 0.39         | $ 1.43         | $ 1.94          |

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+ References
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| - Definition
The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
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| - Definition
The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.
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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.
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| - Definition
The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.
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| X                                                                                                                                                                                         |
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