Securities Available-for-Sale - Fair Value and Age of Gross Unrealized Losses by Investment Category (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014 security	Dec. 31, 2013 security
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	39	41
Available-for-sale Securities, Less Than 12 Months, Fair Value	$ 294,095	$ 274,942
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(4,295)	(6,913)
Available-for-sale, Securities, 12 Months or More, Number of Positions	2	2
Available-for-sale Securities, 12 Months or More, Fair Value	10,370	10,088
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(548)	(863)
Available-for-sale Securities, Fair Value, Total	304,465	285,030
Available-for-sale, Securities, Number of Positions	41	43
Available-for-sale Securities, Unrealized Losses, Total	(4,843)	(7,776)
Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	19	16
Available-for-sale Securities, Less Than 12 Months, Fair Value	171,730	126,017
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(2,216)	(2,581)
Available-for-sale, Securities, 12 Months or More, Number of Positions	0	0
Available-for-sale Securities, 12 Months or More, Fair Value	0	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	0	0
Available-for-sale Securities, Fair Value, Total	171,730	126,017
Available-for-sale, Securities, Number of Positions	19	16
Available-for-sale Securities, Unrealized Losses, Total	(2,216)	(2,581)
Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	3	3
Available-for-sale Securities, Less Than 12 Months, Fair Value	39,265	39,522
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(368)	(603)
Available-for-sale, Securities, 12 Months or More, Number of Positions	0	0
Available-for-sale Securities, 12 Months or More, Fair Value	0	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	0	0
Available-for-sale Securities, Fair Value, Total	39,265	39,522
Available-for-sale, Securities, Number of Positions	3	3
Available-for-sale Securities, Unrealized Losses, Total	(368)	(603)
Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	3	2
Available-for-sale Securities, Less Than 12 Months, Fair Value	23,002	22,822
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(391)	(685)
Available-for-sale, Securities, 12 Months or More, Number of Positions	0	0
Available-for-sale Securities, 12 Months or More, Fair Value	0	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	0	0
Available-for-sale Securities, Fair Value, Total	23,002	22,822
Available-for-sale, Securities, Number of Positions	3	2
Available-for-sale Securities, Unrealized Losses, Total	(391)	(685)
Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	3	4
Available-for-sale Securities, Less Than 12 Months, Fair Value	30,436	39,052
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(919)	(1,305)
Available-for-sale, Securities, 12 Months or More, Number of Positions	0	0
Available-for-sale Securities, 12 Months or More, Fair Value	0	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	0	0
Available-for-sale Securities, Fair Value, Total	30,436	39,052
Available-for-sale, Securities, Number of Positions	3	4
Available-for-sale Securities, Unrealized Losses, Total	(919)	(1,305)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	11	16
Available-for-sale Securities, Less Than 12 Months, Fair Value	29,662	47,529
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(401)	(1,739)
Available-for-sale, Securities, 12 Months or More, Number of Positions	2	2
Available-for-sale Securities, 12 Months or More, Fair Value	10,370	10,088
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(548)	(863)
Available-for-sale Securities, Fair Value, Total	40,032	57,617
Available-for-sale, Securities, Number of Positions	13	18
Available-for-sale Securities, Unrealized Losses, Total	(949)	(2,602)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	39	41
Available-for-sale Securities, Less Than 12 Months, Fair Value	294,095	274,942
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(4,295)	(6,913)
Available-for-sale, Securities, 12 Months or More, Number of Positions	2	2
Available-for-sale Securities, 12 Months or More, Fair Value	10,370	10,088
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(548)	(863)
Available-for-sale Securities, Fair Value, Total	304,465	285,030
Available-for-sale, Securities, Number of Positions	41	43
Available-for-sale Securities, Unrealized Losses, Total	(4,843)	(7,776)
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	0	0
Available-for-sale Securities, Less Than 12 Months, Fair Value	0	0
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	0	0
Available-for-sale, Securities, 12 Months or More, Number of Positions	0	0
Available-for-sale Securities, 12 Months or More, Fair Value	0	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	0	0
Available-for-sale Securities, Fair Value, Total	0	0
Available-for-sale, Securities, Number of Positions	0	0
Available-for-sale Securities, Unrealized Losses, Total	$ 0	$ 0