Disclosures About Fair Value of Assets and Liabilities - Estimated Fair Values of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets:
Investment securities available for sale	$ 538,055us-gaap_AvailableForSaleSecurities	$ 549,543us-gaap_AvailableForSaleSecurities
Investment securities held to maturity	670,611	647,723
Loans held for sale	6,392us-gaap_LoansReceivableHeldForSaleNet	7,235us-gaap_LoansReceivableHeldForSaleNet
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	89,243	118,616
Interest-bearing time deposits	83,228	47,520
Liabilities:
Deposits	3,518,556	3,523,199
Significant Other Observable Inputs (Level 2)
Assets:
Investment securities available for sale	531,857	542,897
Investment securities held to maturity	638,360	614,457
Loans held for sale	6,392	7,235
Federal Reserve Bank and Federal Home Loan Bank stock	41,273	41,353
Interest rate swap and cap asset	4,851	3,867
Interest receivable	19,557	19,984
Liabilities:
Deposits	1,116,309	1,099,610
Borrowings:
Federal funds purchased		15,381
Securities sold under repurchase agreements	134,035	124,539
Federal Home Loan Bank advances	167,903	146,669
Subordinated debentures and term loans	85,413	92,802
Interest rate swap liability	8,569	6,537
Interest payable	3,685	3,201
Significant Unobservable Inputs (Level 3)
Assets:
Investment securities available for sale	6,198	6,646
Investment securities held to maturity	32,251	33,266
Loans	3,867,719	3,810,912
Carrying Amount
Assets:
Cash and cash equivalents	89,243	118,616
Interest-bearing time deposits	83,228	47,520
Investment securities available for sale	538,055	549,543
Investment securities held to maturity	651,418	631,088
Loans held for sale	6,392	7,235
Loans	3,902,731	3,860,901
Federal Reserve Bank and Federal Home Loan Bank stock	41,273	41,353
Interest rate swap and cap asset	4,851	3,867
Interest receivable	19,557	19,984
Liabilities:
Deposits	4,648,075	4,640,694
Borrowings:
Federal funds purchased		15,381
Securities sold under repurchase agreements	134,023	124,539
Federal Home Loan Bank advances	166,326	145,264
Subordinated debentures and term loans	126,875	126,810
Interest rate swap liability	8,569	6,537
Interest payable	$ 3,685	$ 3,201

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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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-Subparagraph (SX 210.9-03.13(3)(a))

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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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