Carrying Amount and Fair Value of Company's Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Assets
Available-for-sale securities	$ 550,158	$ 534,358
Held-to-maturity securities	639	832
FDIC indemnification asset	40,389	48,149	49,155
Accrued interest receivable	8,010	7,842
Carrying (Reported) Amount, Fair Value Disclosure
Assets
Cash and cash equivalents	82,119	144,847
Available-for-sale securities	550,158	534,358
Held-to-maturity securities	627	816
Loans held for sale	4,621	6,672
Loans held for investment less allowance	1,668,376	1,698,883
FDIC indemnification asset	40,389	48,149
Accrued interest receivable	8,010	7,842
Derivative financial assets	17	144
Deferred compensation assets	3,861	3,625
Liabilities
Securities sold under agreements to repurchase	121,204	136,118
Accrued interest payable	2,308	2,481
FHLB and other indebtedness	165,877	177,435
Derivative financial liabilities	163	16
Deferred compensation liabilities	3,861	3,625
Carrying (Reported) Amount, Fair Value Disclosure \| Demand Deposits
Liabilities
Deposits Fair Value	349,972	343,352
Carrying (Reported) Amount, Fair Value Disclosure \| Interest-bearing Deposits
Liabilities
Deposits Fair Value	354,862	353,321
Carrying (Reported) Amount, Fair Value Disclosure \| Savings Deposits
Liabilities
Deposits Fair Value	513,781	500,276
Carrying (Reported) Amount, Fair Value Disclosure \| Bank Time Deposits
Liabilities
Deposits Fair Value	770,081	833,226
Estimate of Fair Value, Fair Value Disclosure
Assets
Cash and cash equivalents	82,119	144,847
Available-for-sale securities	550,158	534,358
Held-to-maturity securities	639	832
Loans held for sale	4,640	6,774
Loans held for investment less allowance	1,658,347	1,702,128
FDIC indemnification asset	40,389	48,149
Accrued interest receivable	8,010	7,842
Derivative financial assets	17	144
Deferred compensation assets	3,861	3,625
Liabilities
Securities sold under agreements to repurchase	124,427	142,417
Accrued interest payable	2,308	2,481
FHLB and other indebtedness	179,299	200,418
Derivative financial liabilities	163	16
Deferred compensation liabilities	3,861	3,625
Estimate of Fair Value, Fair Value Disclosure \| Demand Deposits
Liabilities
Deposits Fair Value	349,972	343,352
Estimate of Fair Value, Fair Value Disclosure \| Interest-bearing Deposits
Liabilities
Deposits Fair Value	354,862	353,321
Estimate of Fair Value, Fair Value Disclosure \| Savings Deposits
Liabilities
Deposits Fair Value	513,781	500,276
Estimate of Fair Value, Fair Value Disclosure \| Bank Time Deposits
Liabilities
Deposits Fair Value	775,067	842,331
Level 1
Assets
Cash and cash equivalents	82,119	144,847
Available-for-sale securities	5,413	3,511
Deferred compensation assets	3,861	3,625
Liabilities
Deferred compensation liabilities	3,861	3,625
Level 2
Assets
Available-for-sale securities	544,745	530,847
Held-to-maturity securities	639	832
Loans held for sale	4,640	6,774
Accrued interest receivable	8,010	7,842
Derivative financial assets	17	144
Liabilities
Securities sold under agreements to repurchase	124,427	142,417
Accrued interest payable	2,308	2,481
FHLB and other indebtedness	179,299	200,418
Derivative financial liabilities	163	16
Level 2 \| Demand Deposits
Liabilities
Deposits Fair Value	349,972	343,352
Level 2 \| Interest-bearing Deposits
Liabilities
Deposits Fair Value	354,862	353,321
Level 2 \| Savings Deposits
Liabilities
Deposits Fair Value	513,781	500,276
Level 2 \| Bank Time Deposits
Liabilities
Deposits Fair Value	775,067	842,331
Level 3
Assets
Loans held for investment less allowance	1,658,347	1,702,128
FDIC indemnification asset	$ 40,389	$ 48,149

Deferred compensation assets fair value.

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Deferred compensation liabilities fair value.

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Loans held for investment less allowance.

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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, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Carrying amount of receivable assets originating from the indemnification agreement with the Federal Deposit Insurance Corporation (FDIC), in which the FDIC is to partially cover losses.

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

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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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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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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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