Disclosures About Fair Value of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets:
Investment securities available for sale	$ 1,149,162	$ 999,947
Investment securities held to maturity	468,452	568,208
Loans held for sale	3,022	7,216
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	142,501	154,905
Interest-bearing time deposits	66,763	35,027
Investment securities available for sale
Liabilities:
Deposits	6,083,491	5,741,019
Significant Other Observable Inputs (Level 2)
Borrowings:
Federal funds purchased	90,000	144,038
Securities sold under repurchase agreements	118,696	136,562
Federal Home Loan Bank advances	379,309	361,085
Subordinated debentures and term loans	124,806	120,085
Assets:
Investment securities available for sale	1,145,847	995,969
Investment securities held to maturity	458,087	556,305
Loans held for sale	3,022	7,216
Federal Home Loan Bank stock	24,588	23,825
Interest rate swap and cap asset	14,311	7,323
Interest receivable	38,531	37,130
Liabilities:
Deposits	1,522,591	1,406,526
Interest rate swap liability	14,150	8,688
Interest payable	5,920	4,390
Significant Unobservable Inputs (Level 3)
Assets:
Investment securities available for sale	3,315	3,978
Investment securities held to maturity	10,365	11,903
Loans	6,793,227	6,534,877
Carrying Amount
Borrowings:
Federal funds purchased	90,000	144,038
Securities sold under repurchase agreements	118,824	136,623
Federal Home Loan Bank advances	385,458	414,377
Subordinated debentures and term loans	138,408	139,349
Assets:
Cash and cash equivalents	142,501	154,905
Interest-bearing time deposits	66,763	35,027
Investment securities available for sale	1,149,162	999,947
Investment securities held to maturity	476,089	560,655
Loans held for sale	3,022	7,216
Loans	7,009,665	6,676,167
Federal Home Loan Bank stock	24,588	23,825
Interest rate swap and cap asset	14,311	7,323
Interest receivable	38,531	37,130
Liabilities:
Deposits	7,633,152	7,172,530
Interest rate swap liability	14,150	8,688
Interest payable	$ 5,920	$ 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 security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
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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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-Publisher FASB
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