Securities Available-for-Sale - Amortized Cost and Fair Value of Available-for-Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 548,395	$ 510,399
Fair Value	551,896	509,425
Obligations of U.S. Government Corporations and Agencies, and Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	14,180
Due after one year through five years, Amortized Cost	183,013
Due after five years through ten years, Amortized Cost	103,528
Due after ten years, Amortized Cost	91,235
Available-for-sale Securities, Debt Maturities, Amortized Cost	391,956
Due in one year or less, Fair Value	14,306
Due after one year through five years, Fair Value	183,694
Due after five years through ten years, Fair Value	103,277
Due after ten years, Fair Value	92,104
Fair Value, Debt securities	393,381
Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	62,114	63,776
Fair Value	62,439	63,774
Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	46,519	47,934
Fair Value	47,552	48,669
Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	40,227	40,357
Fair Value	39,321	39,052
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	540,816	502,820
Fair Value	542,693	500,510
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,579	7,579
Fair Value	$ 9,203	$ 8,915