Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	$ 326,117us-gaap_AvailableForSaleSecurities	$ 519,820us-gaap_AvailableForSaleSecurities
Derivatives assets	5us-gaap_DerivativeAssets	84us-gaap_DerivativeAssets
Derivative Liabilities	214us-gaap_DerivativeLiabilities	41us-gaap_DerivativeLiabilities
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	326,117	519,820
Fair value loans	3,406	4,404
Deferred compensation assets	3,380	4,200
Derivatives assets	5	84
Deferred compensation liabilities	3,380	4,200
Derivative Liabilities	214	41
Recurring \| US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities		9,013
Recurring \| Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	138,915	144,280
Recurring \| Single Issue Trust Preferred Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	46,137	46,234
Recurring \| Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	5,109	4,871
Recurring \| Agency Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	102,119	300,386
Recurring \| Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	239	5,247
Recurring \| Forward Sale Loan Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives assets	5	41
Recurring \| U.S. Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	33,598
Recurring \| Non Agency Residential Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities		9,789
Interest Rate Swaps Agreement \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives assets		43
Derivative Liabilities	209
IRLCs \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	5	41
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	221	251
Level 1 \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	221	251
Deferred compensation assets	3,380	4,200
Deferred compensation liabilities	3,380	4,200
Level 1 \| Recurring \| Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	221	251
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	325,896	519,569
Fair value loans	3,406	4,404
Derivatives assets	5	84
Derivative Liabilities	214	41
Level 2 \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	325,896	519,569
Fair value loans	3,406	4,404
Derivatives assets	5	84
Derivative Liabilities	214	41
Level 2 \| Recurring \| US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities		9,013
Level 2 \| Recurring \| Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	138,915	144,280
Level 2 \| Recurring \| Single Issue Trust Preferred Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	46,137	46,234
Level 2 \| Recurring \| Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	5,109	4,871
Level 2 \| Recurring \| Agency Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	102,119	300,386
Level 2 \| Recurring \| Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	18	4,996
Level 2 \| Recurring \| Forward Sale Loan Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives assets	5	41
Level 2 \| Recurring \| U.S. Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	33,598
Level 2 \| Recurring \| Non Agency Residential Mortgage Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities		9,789
Level 2 \| Interest Rate Swaps Agreement \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives assets		43
Derivative Liabilities	209
Level 2 \| IRLCs \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	$ 5	$ 41

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Deferred compensation liabilities.

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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 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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