Fair Values of Financial Instruments - Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Investment securities available for sale	$ 658,400	$ 549,543
Investment securities held to maturity	632,380	647,723
Loans held for sale	9,894	7,235
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	102,170	118,616
Interest-bearing time deposits	32,315	47,520
Liabilities:
Deposits	4,095,004	3,532,199
Significant Other Observable Inputs (Level 2)
Assets:
Investment securities available for sale	652,468	542,897
Investment securities held to maturity	598,082	614,457
Loans held for sale	9,894	7,235
Federal Reserve and Federal Home Loan Bank stock	37,633	41,353
Interest rate swap asset	4,974	3,867
Interest receivable	24,415	19,984
Liabilities:
Deposits	1,177,142	1,099,610
Borrowings:
Federal funds purchased	49,721	15,381
Securities sold under repurchase agreements	155,325	124,539
Federal Home Loan Bank advances	236,375	146,669
Subordinated debentures and term loans	103,643	92,802
Interest rate swap liability	8,070	6,537
Interest payable	3,092	3,201
Significant Unobservable Inputs (Level 3)
Assets:
Investment securities available for sale	5,932	6,646
Investment securities held to maturity	34,298	33,266
Loans	4,539,940	3,810,912
Carrying Amount
Assets:
Cash and cash equivalents	102,170	118,616
Interest-bearing time deposits	32,315	47,520
Investment securities available for sale	658,400	549,543
Investment securities held to maturity	618,599	631,088
Loans held for sale	9,894	7,235
Loans	4,631,369	3,860,901
Federal Reserve and Federal Home Loan Bank stock	37,633	41,353
Interest rate swap asset	4,974	3,867
Interest receivable	24,415	19,984
Liabilities:
Deposits	5,289,647	4,640,694
Borrowings:
Federal funds purchased	49,721	15,381
Securities sold under repurchase agreements	155,325	124,539
Federal Home Loan Bank advances	235,652	145,264
Subordinated debentures and term loans	127,846	126,810
Interest rate swap liability	8,070	6,537
Interest payable	$ 3,092	$ 3,201

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

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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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