Disclosures About Fair Value of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets:
Investment securities available for sale	$ 567,996	$ 536,201
Investment securities held to maturity	634,555	560,847
Loans held for sale	6,423	5,331
Carrying Amount
Assets:
Cash and due from banks	74,237	109,434
Interest-bearing time deposits	24,171	55,069
Investment securities available for sale	567,996	536,201
Investment securities held to maturity	621,818	559,378
Loans held for sale	6,423	5,331
Loans	3,706,871	3,564,539
Federal Reserve Bank and Federal Home Loan Bank stock	43,127	38,990
Interest rate swap and cap asset	3,109	4,009
Interest receivable	19,455	18,672
Liabilities:
Deposits	4,310,123	4,231,468
Borrowings:
Federal funds purchased	61,428	125,645
Securities sold under repurchase agreements	117,892	148,672
Federal Home Loan Bank advances	255,423	122,140
Subordinated debentures and term loans	126,874	126,807
Interest rate swap liability	4,547	3,953
Interest payable	3,819	1,771
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and due from banks	74,237	109,434
Interest-bearing time deposits	24,171	55,069
Liabilities:
Deposits	3,229,034	3,082,117
Significant Other Observable Inputs (Level 2)
Assets:
Investment securities available for sale	560,509	526,224
Investment securities held to maturity	595,817	525,998
Loans held for sale	6,423	5,331
Federal Reserve Bank and Federal Home Loan Bank stock	43,127	38,990
Interest rate swap and cap asset	3,109	4,009
Interest receivable	19,455	18,672
Liabilities:
Deposits	1,073,638	934,937
Borrowings:
Federal funds purchased	61,428	125,645
Securities sold under repurchase agreements	117,903	148,852
Federal Home Loan Bank advances	255,569	122,962
Subordinated debentures and term loans	101,257	82,607
Interest rate swap liability	4,547	3,953
Interest payable	3,819	1,771
Significant Unobservable Inputs (Level 3)
Assets:
Investment securities available for sale	7,487	9,977
Investment securities held to maturity	38,738	34,849
Loans	$ 3,667,454	$ 3,506,615

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Federal Home Loan Bank Advances Fair Value

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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 Rate Swap Liabilities Fair Value Disclosure

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Interest Rate Swaps Assets 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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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 of investments in debt securities classified as held-to-maturity.

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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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Amount classified as loans attributable to disposal group held for sale or disposed of. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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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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