Securities - Fair Value of Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	$ 514,839	$ 508,427
Gross Unrealized Gains	10,476	9,015
Held-to-maturity, Amortized Cost	9,910	9,910
Gross Unrealized Losses	(5,885)	(8,851)
Available-for-sale Securities, Fair Value	519,430	508,591
Held-to-maturity, Fair Value	9,910	9,910
U.S. Treasury and federal agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	43,098	43,808
Gross Unrealized Gains	121	133
Gross Unrealized Losses	(578)	(807)
Available-for-sale Securities, Fair Value	42,641	43,134
State and municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	174,538	176,670
Gross Unrealized Gains	5,623	4,405
Held-to-maturity, Amortized Cost	9,910	9,910
Gross Unrealized Losses	(1,828)	(3,177)
Held-to-maturity, Gross Unrealized Gains
Available-for-sale Securities, Fair Value	178,333	177,898
Held-to-maturity, Gross Unrealized Losses
Held-to-maturity, Fair Value	9,910	9,910
Federal agency collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	115,584	116,047
Gross Unrealized Gains	1,126	1,242
Gross Unrealized Losses	(1,874)	(2,583)
Available-for-sale Securities, Fair Value	114,836	114,706
Federal agency mortgage-backed pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	179,625	170,006
Gross Unrealized Gains	3,553	3,172
Gross Unrealized Losses	(1,605)	(2,284)
Available-for-sale Securities, Fair Value	181,573	170,894
Private labeled mortgage-backed pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	1,024	1,188
Gross Unrealized Gains	32	38
Gross Unrealized Losses
Available-for-sale Securities, Fair Value	1,056	1,226
Corporate notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	970	708
Gross Unrealized Gains	21	25
Gross Unrealized Losses
Available-for-sale Securities, Fair Value	$ 991	$ 733