| **Acquisitions - Narrative (Details) $ / shares in Units, $ in Thousands** |           |           |          | 3 Months Ended | 12 Months Ended |
|----------------------------------------------------------------------------|-----------|-----------|----------|----------------|-----------------|
||
| IAB                                                                        |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Shares purchased (in shares) | shares                                      |      |      | 495,112  |           |            |
| Percentage of interest acquired                                            |      |      | 12.10%   | 12.10%         |            |
| Value of acquired shares                                                   |      |      | $ 19,800 |           |            |
| Purchase price per share (usd per share) | $ / shares                      |      |      | $ 40.00  |           |            |
| Number of banking centers acquired | bank_branch                           | 16        |      |     |           |            |
| Stock issued as a part of acquisition (in shares) | shares                 | 6,000,000 |      |     |           |            |
| Issuance of common stock related to acquisition                            | $ 238,800 |      |     |           |            |
| Total purchase price                                                       | 258,600   |      |     |           |            |
| Fair value of equity interest after adjustment                             |      |      |     | $ 19,800       |            |
| Remeasurement loss                                                         |      |      |     | $ 50           |            |
| Other intangible assets                                                    | 17,403    |      |     |           |            |
| Operating revenue                                                          |      |      |     |           | $ 21,400        |
| IAB | Core deposits                                                        |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Other intangible assets                                                    | $ 13,638  |      |     |           |            |
| Acquired intangible asset, expected useful life                            | 10 years  |      |     |           |            |
| IAB | Noncompete agreements                                                |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Other intangible assets                                                    | $ 3,765   |      |     |           |            |
| Acquired intangible asset, expected useful life                            | 2 years   |      |     |           |            |
| IAB | Common Stock                                                         |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Number of shares of common stock                                           | 1.653     |      |     |           |            |
| Arlington Bank                                                             |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Percentage of interest acquired                                            |      | 100.00%   |     |           |            |
| Number of banking centers acquired | bank_branch                           |      | 3         |     |           |            |
| Stock issued as a part of acquisition (in shares) | shares                 |      | 2,100,000 |     |           |            |
| Issuance of common stock related to acquisition                            |      | $ 82,600  |     |           |            |
| Other intangible assets                                                    |      | 4,526     |     |           |            |
| Operating revenue                                                          |      |      |     |           | 9,000           |
| Arlington Bank | Core deposits                                             |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Other intangible assets                                                    |      | $ 4,526   |     |           |            |
| Acquired intangible asset, expected useful life                            |      | 10 years  |     |           |            |
| Arlington Bank | Common Stock                                              |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Number of shares of common stock                                           |      | 2.7245    |     |           |            |
| Arlington Bank and IAB | Expenses directly attributable to acquisitions    |      |      |     |           |            |
| **Business Acquisition [Line Items]**                                      |      |      |     |           |            |
| Non-recurring expenses                                                     |      |      |     |           | $ 15,400        |

| X                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Business Acquisition, Shares Acquired
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| X                                                                                                                                                                                                                                                                          |
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Business Acquisition, Shares Acquired, Value
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No definition available.
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| X                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Business Combination, Pro Forma Information, Expenses, Net Of Tax
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| X                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Business Combinations, Acquiree, Shares of Stock Received For Each Share Currently Owned
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| X                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of Banking Centers
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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No definition available.
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| - Definition
Percentage of voting equity interests acquired at the acquisition date in the business combination.
+ References
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| - Definition
Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.
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No definition available.
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of identifiable intangible assets recognized as of the acquisition date.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value at acquisition-date of the equity interest in the acquiree held by the acquirer, immediately before the acquisition date for businesses combined in stages.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
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| - Definition
In a business combination achieved in stages, this element represents the amount of loss recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.
+ References
No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of shares of stock issued during the period pursuant to acquisitions.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Value of stock issued pursuant to acquisitions during the period.
+ References
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