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

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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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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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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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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Fair value portion of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Fair value of investments in debt securities classified as held-to-maturity.

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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.

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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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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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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.

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The face amount of loans that will be sold to other entities.

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Fair value portion of other liabilities.

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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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