Fair Value (Financial Assets and Liabilities at Dates Indicated that Were Accounted for or Disclosed at Fair Value) (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	$ 13,899,000	$ 10,512,000
Investments available-for-sale (at fair value)	657,709,000	672,209,000
Marketable Equity Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	723,000	723,000
Fair Value, Measurements, Recurring | Residential Mortgage Loans Held For Sale
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	13,899,000	10,512,000
Fair Value, Measurements, Recurring | U.S. Government Agencies
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	143,895,000	141,679,000
Fair Value, Measurements, Recurring | State and municipal
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	165,786,000	167,052,000
Fair Value, Measurements, Recurring | Mortgage-Backed
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	346,303,000	361,519,000
Fair Value, Measurements, Recurring | Corporate Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Trust Preferred
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	1,002,000	1,236,000
Fair Value, Measurements, Recurring | Marketable Equity Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	723,000	723,000
Fair Value, Measurements, Recurring | Interest Rate Swap Agreements
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other assets	1,561,000	1,501,000
Other liabilities	(1,561,000)	(1,501,000)
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential Mortgage Loans Held For Sale
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Government Agencies
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and municipal
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-Backed
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Trust Preferred
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Marketable Equity Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest Rate Swap Agreements
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other assets	0	0
Other liabilities	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Residential Mortgage Loans Held For Sale
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	13,899,000	10,512,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Government Agencies
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	143,895,000	141,679,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | State and municipal
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	165,786,000	167,052,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage-Backed
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	346,303,000	361,519,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Trust Preferred
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Marketable Equity Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	723,000	723,000
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest Rate Swap Agreements
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other assets	1,561,000	1,501,000
Other liabilities	(1,561,000)	(1,501,000)
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Residential Mortgage Loans Held For Sale
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Residential mortgage loans held for sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Government Agencies
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | State and municipal
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-Backed
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate Debt
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Trust Preferred
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	1,002,000	1,236,000
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Marketable Equity Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments available-for-sale (at fair value)	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Interest Rate Swap Agreements
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other assets	0	0
Other liabilities	$ 0	$ 0