Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
ASSETS
Total securities available-for-sale	$ 551,896,000	$ 509,425,000
LIABILITIES
Total Liabilities		0
Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	264,184,000	234,751,000
Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	62,439,000	63,774,000
Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	47,552,000	48,669,000
Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	39,321,000	39,052,000
Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale	129,197,000	114,264,000
Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	9,203,000	8,915,000
Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale	551,896,000	509,425,000
Trading securities held in a Rabbi Trust	2,931,000	2,864,000
Total securities	554,827,000	512,289,000
Total Assets	568,358,000	526,106,000
LIABILITIES
Total Liabilities	13,390,000	13,647,000
Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	264,184,000	234,751,000
Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	62,439,000	63,774,000
Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	47,552,000	48,669,000
Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	39,321,000	39,052,000
Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale	129,197,000	114,264,000
Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	9,203,000	8,915,000
Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets	13,433,000	13,698,000
LIABILITIES
Derivative financial liabilities	13,390,000	13,647,000
Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets	93,000	85,000
Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets	5,000	34,000
Level 1 [Member] | Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale	190,000	202,000
Trading securities held in a Rabbi Trust	2,931,000	2,864,000
Total securities	3,121,000	3,066,000
Total Assets	3,121,000	3,066,000
LIABILITIES
Total Liabilities
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	190,000	202,000
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets
LIABILITIES
Derivative financial liabilities
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets
Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets
Level 2 [Member] | Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale	551,706,000	509,223,000
Trading securities held in a Rabbi Trust
Total securities	551,706,000	509,223,000
Total Assets	565,237,000	523,040,000
LIABILITIES
Total Liabilities	13,390,000	13,647,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	264,184,000	234,751,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	62,439,000	63,774,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	47,552,000	48,669,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale	39,321,000	39,052,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale	129,197,000	114,264,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale	9,013,000	8,713,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets	13,433,000	13,698,000
LIABILITIES
Derivative financial liabilities	13,390,000	13,647,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets	93,000	85,000
Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets	5,000	34,000
Level 3 [Member] | Fair Value Measurements, Recurring [Member]
ASSETS
Total securities available-for-sale
Trading securities held in a Rabbi Trust
Total securities
Total Assets
LIABILITIES
Total Liabilities
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Obligations of States and Political Subdivisions [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Marketable Equity Securities [Member]
ASSETS
Total securities available-for-sale
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Swaps [Member]
ASSETS
Derivative financial assets
LIABILITIES
Derivative financial liabilities
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Interest Rate Lock Commitments [Member]
ASSETS
Derivative financial assets
Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Forward Sale Contracts [Member]
ASSETS
Derivative financial assets