| **Disclosures About Fair Value of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands** | Mar. 31, 2018 | Dec. 31, 2017 |
|------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Assets:**                                                                                                                                    |          |          |
| Investment securities available for sale                                                                                                       | $ 1,003,799   | $ 999,947     |
| Investment securities held to maturity                                                                                                         | 538,399       | 568,208       |
| Loans held for sale                                                                                                                            | 4,469         | 7,216         |
| Quoted Prices in Active Markets for Identical Assets (Level 1)                                                                                 |          |          |
| **Assets:**                                                                                                                                    |          |          |
| Cash and cash equivalents                                                                                                                      | 128,828       | 154,905       |
| Interest-bearing time deposits                                                                                                                 | 24,233        | 35,027        |
| Investment securities available for sale                                                                                                       |               |               |
| **Liabilities:**                                                                                                                               |          |          |
| Deposits                                                                                                                                       | 5,849,466     | 5,741,019     |
| Significant Other Observable Inputs (Level 2)                                                                                                  |          |          |
| **Assets:**                                                                                                                                    |          |          |
| Investment securities available for sale                                                                                                       | 999,833       | 995,969       |
| Investment securities held to maturity                                                                                                         | 527,253       | 556,305       |
| Loans held for sale                                                                                                                            | 4,469         | 7,216         |
| Federal Home Loan Bank stock                                                                                                                   | 24,588        | 23,825        |
| Interest rate swap and cap asset                                                                                                               | 11,634        | 7,323         |
| Interest receivable                                                                                                                            | 35,223        | 37,130        |
| **Liabilities:**                                                                                                                               |          |          |
| Deposits                                                                                                                                       | 1,450,066     | 1,406,526     |
| **Borrowings:**                                                                                                                                |          |          |
| Federal funds purchased                                                                                                                        | 50,000        | 144,038       |
| Securities sold under repurchase agreements                                                                                                    | 138,770       | 136,562       |
| Federal Home Loan Bank advances                                                                                                                | 443,804       | 361,085       |
| Subordinated debentures and term loans                                                                                                         | 123,485       | 120,085       |
| Interest rate swap liability                                                                                                                   | 12,065        | 8,688         |
| Interest payable                                                                                                                               | 5,376         | 4,390         |
| Significant Unobservable Inputs (Level 3)                                                                                                      |          |          |
| **Assets:**                                                                                                                                    |          |          |
| Investment securities available for sale                                                                                                       | 3,966         | 3,978         |
| Investment securities held to maturity                                                                                                         | 11,146        | 11,903        |
| Loans                                                                                                                                          | 6,649,237     | 6,534,877     |
| Carrying Amount                                                                                                                                |          |          |
| **Assets:**                                                                                                                                    |          |          |
| Cash and cash equivalents                                                                                                                      | 128,828       | 154,905       |
| Interest-bearing time deposits                                                                                                                 | 24,233        | 35,027        |
| Investment securities available for sale                                                                                                       | 1,003,799     | 999,947       |
| Investment securities held to maturity                                                                                                         | 540,021       | 560,655       |
| Loans held for sale                                                                                                                            | 4,469         | 7,216         |
| Loans                                                                                                                                          | 6,825,276     | 6,676,167     |
| Federal Home Loan Bank stock                                                                                                                   | 24,588        | 23,825        |
| Interest rate swap and cap asset                                                                                                               | 11,634        | 7,323         |
| Interest receivable                                                                                                                            | 35,223        | 37,130        |
| **Liabilities:**                                                                                                                               |          |          |
| Deposits                                                                                                                                       | 7,327,635     | 7,172,530     |
| **Borrowings:**                                                                                                                                |          |          |
| Federal funds purchased                                                                                                                        | 50,000        | 144,038       |
| Securities sold under repurchase agreements                                                                                                    | 138,910       | 136,623       |
| Federal Home Loan Bank advances                                                                                                                | 449,419       | 414,377       |
| Subordinated debentures and term loans                                                                                                         | 138,297       | 139,349       |
| Interest rate swap liability                                                                                                                   | 12,065        | 8,688         |
| Interest payable                                                                                                                               | $ 5,376       | $ 4,390       |

| X                                                                                                                                                                                                                                |
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Borrowed Funds [Abstract]
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| - Definition
Interest Bearing Deposits with Banks, Fair Value Disclosure
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Interest Payable Fair Value Disclosure
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Interest Receivable, Fair Value Disclosure
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.
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| - Definition
Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of short term borrowing where a bank borrows, at the federal funds rate, from another bank.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of investments in debt securities classified as held-to-maturity.
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| - Definition
Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.
+ References
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| - Definition
Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.
+ References
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| - Definition
The face amount of loans that will be sold to other entities.
+ References
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| - Definition
Fair value portion of other liabilities.
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| - Definition
Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.
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