Fair Value - Carrying Amount and Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 51,635	$ 27,928	$ 33,866	$ 29,633
Interest bearing time deposits with other banks	225us-gaap_TimeDepositsAtCarryingValue	225us-gaap_TimeDepositsAtCarryingValue
Securities available for sale	655,400us-gaap_AvailableForSaleSecurities	685,720us-gaap_AvailableForSaleSecurities
Trading securities	4,502us-gaap_TradingSecurities	4,505us-gaap_TradingSecurities
Loans held for sale	1,661us-gaap_LoansReceivableHeldForSaleNet	887us-gaap_LoansReceivableHeldForSaleNet
Net loans	1,338,444	1,337,916
FHLB and other equity interests	4,923	6,695
LIABILITIES
Deposits	(1,867,381)us-gaap_Deposits	(1,847,079)us-gaap_Deposits
Subordinated debentures	(20,620)us-gaap_SubordinatedDebt	(20,620)us-gaap_SubordinatedDebt
Carrying Amount [Member]
ASSETS
Cash and cash equivalents	51,635	27,928
Interest bearing time deposits with other banks	225	225
Securities available for sale	655,400	685,720
Trading securities	4,502	4,505
Loans held for sale	1,661	887
Net loans	1,338,444	1,337,916
FHLB and other equity interests	4,923	6,695
Accrued interest receivable	7,667	7,441
LIABILITIES
Deposits	(1,867,381)	(1,847,079)
FHLB and other borrowings	(75,652)	(111,695)
Subordinated debentures	(20,620)	(20,620)
Interest rate swaps	(974)	(946)
Accrued interest payable	(923)	(804)
Total Fair Value [Member]
ASSETS
Cash and cash equivalents	51,635	27,928
Interest bearing time deposits with other banks	225	224
Securities available for sale	655,400	685,720
Trading securities	4,502	4,505
Loans held for sale	1,712	938
Net loans	1,356,178	1,337,537
Accrued interest receivable	7,667	7,441
LIABILITIES
Deposits	(1,867,553)	(1,846,208)
FHLB and other borrowings	(76,217)	(111,821)
Subordinated debentures	(11,415)	(11,395)
Interest rate swaps	(974)	(946)
Accrued interest payable	(923)	(804)
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
ASSETS
Cash and cash equivalents	51,635	27,928
Interest bearing time deposits with other banks	0	0
Securities available for sale	1,005	1,002
Trading securities	4,290	4,296
Loans held for sale	0	0
Net loans	0	0
Accrued interest receivable	6	5
LIABILITIES
Deposits	(1,655,195)	(1,670,172)
FHLB and other borrowings	0	0
Subordinated debentures	0	0
Interest rate swaps	0	0
Accrued interest payable	(362)	(358)
Significant Other Observable Inputs (Level 2) [Member]
ASSETS
Cash and cash equivalents	0	0
Interest bearing time deposits with other banks	225	224
Securities available for sale	653,490	683,813
Trading securities	212	209
Loans held for sale	1,712	938
Net loans	0	0
Accrued interest receivable	3,850	3,503
LIABILITIES
Deposits	(212,358)	(176,036)
FHLB and other borrowings	(76,217)	(111,821)
Subordinated debentures	(11,415)	(11,395)
Interest rate swaps	(974)	(946)
Accrued interest payable	(545)	(430)
Significant Unobservable Inputs (Level 3) [Member]
ASSETS
Cash and cash equivalents	0	0
Interest bearing time deposits with other banks	0	0
Securities available for sale	905	905
Trading securities	0	0
Loans held for sale	0	0
Net loans	1,356,178	1,337,537
Accrued interest receivable	3,811	3,933
LIABILITIES
Deposits	0	0
FHLB and other borrowings	0	0
Subordinated debentures	0	0
Interest rate swaps	0	0
Accrued interest payable	$ (16)	$ (16)

Federal home loan bank treasury tax and loan and other borrowings.

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

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Amount 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Amount of interest payable on debt, including, but not limited to, trade payables.

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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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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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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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Includes other investments and securities that are not at fair value as of the balance sheet date and those that are not accounted for under the equity method.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Any certificate of deposit or savings account held by a bank or other financial institution for a short-term specified period of time. Because of their short-term, time deposits are considered 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. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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