Securities - Gross Unrealized Losses and Fair Value of Company's Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	$ 241,541	$ 41,837
Fair value more than 12 months	11,807
Total fair value	253,348	41,837
Unrealized losses less than 12 months	(8,205)	(168)
Unrealized losses more than 12 months	(646)
Total unrealized losses	(8,851)	(168)
U.S. Treasury and federal agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	32,099	13,064
Fair value more than 12 months
Total fair value	32,099	13,064
Unrealized losses less than 12 months	(807)	(30)
Unrealized losses more than 12 months
Total unrealized losses	(807)	(30)
State and municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	57,078	11,928
Fair value more than 12 months	3,206
Total fair value	60,284	11,928
Unrealized losses less than 12 months	(2,993)	(84)
Unrealized losses more than 12 months	(184)
Total unrealized losses	(3,177)	(84)
Federal agency collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	64,445	12,719
Fair value more than 12 months	8,601
Total fair value	73,046	12,719
Unrealized losses less than 12 months	(2,121)	(39)
Unrealized losses more than 12 months	(462)
Total unrealized losses	(2,583)	(39)
Federal agency mortgage-backed pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value less than 12 months	87,919	4,126
Fair value more than 12 months
Total fair value	87,919	4,126
Unrealized losses less than 12 months	(2,284)	(15)
Unrealized losses more than 12 months
Total unrealized losses	$ (2,284)	$ (15)