| **Acquisitions - Schedule of Acquired Loan Data (Details) (Details) - USD ($) $ in Thousands**                      | Dec. 31, 2017 | Jul. 14, 2017 | May 19, 2017 |
|---------------------------------------------------------------------------------------------------------------------|---------------|---------------|--------------|
| **Business Acquisition [Line Items]**                                                                               |          |          |         |
| Fair Value of Acquired Loans at Acquisition Date, subject to ASC 310-30                                             | $ 7,463       |          |         |
| Gross Contractual Amounts Receivable at Acquisition Date, subject to ASC 310-30                                     | 20,314        |          |         |
| IAB                                                                                                                 |          |          |         |
| **Business Acquisition [Line Items]**                                                                               |          |          |         |
| Fair Value of Acquired Loans at Acquisition Date, subject to ASC 310-30                                             | 4,838         | $ 4,838       |         |
| Gross Contractual Amounts Receivable at Acquisition Date, subject to ASC 310-30                                     | 14,131        | 14,131        |         |
| Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, subject to ASC 310-30     |          | 8,352         |         |
| Fair Value of Acquired Loans at Acquisition Date, not subject to ASC 310-30                                         |          | 720,544       |         |
| Gross Contractual Amounts Receivable at Acquisition Date, not subject to ASC 310-30                                 |          | 864,613       |         |
| Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, not subject to ASC 310-30 |          | $ 9,786       |         |
| Arlington Bank                                                                                                      |          |          |         |
| **Business Acquisition [Line Items]**                                                                               |          |          |         |
| Fair Value of Acquired Loans at Acquisition Date, subject to ASC 310-30                                             | 2,625         |          | $ 2,625      |
| Gross Contractual Amounts Receivable at Acquisition Date, subject to ASC 310-30                                     | $ 6,183       |          | 6,183        |
| Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, subject to ASC 310-30     |          |          | 2,891        |
| Fair Value of Acquired Loans at Acquisition Date, not subject to ASC 310-30                                         |          |          | 222,055      |
| Gross Contractual Amounts Receivable at Acquisition Date, not subject to ASC 310-30                                 |          |          | 308,857      |
| Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected, not subject to ASC 310-30 |          |          | $ 2,741      |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, Cash Flows Not Expected to be Collected at Acquisition
+ References
No definition available.
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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.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the best estimate at the acquisition date of the contractual cash flows not expected to be collected, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of acquired receivable from business combination, excluding certain loans and debt securities acquired in transfer.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the gross contractual amounts receivable, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of contractually required payments receivable at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.
+ References
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| X                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|
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