Securities - Fair Value of Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	$ 508,427	$ 463,306
Held-to-maturity, Amortized Cost	9,910
Gross Unrealized Gains	9,015	19,663
Gross Unrealized Losses	(8,851)	(168)
Available-for-sale Securities, Fair Value	508,591	482,801
Held-to-maturity, Fair Value	9,910	0
U.S. Treasury and federal agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	43,808	51,458
Gross Unrealized Gains	133	351
Gross Unrealized Losses	(807)	(30)
Available-for-sale Securities, Fair Value	43,134	51,779
State and municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	176,670	162,147
Held-to-maturity, Amortized Cost	9,910
Gross Unrealized Gains	4,405	10,842
Held-to-maturity, Gross Unrealized Gains
Gross Unrealized Losses	(3,177)	(84)
Held-to-maturity, Gross Unrealized Losses
Available-for-sale Securities, Fair Value	177,898	172,905
Held-to-maturity, Fair Value	9,910
Federal agency collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	116,047	95,337
Gross Unrealized Gains	1,242	1,533
Gross Unrealized Losses	(2,583)	(39)
Available-for-sale Securities, Fair Value	114,706	96,831
Federal agency mortgage-backed pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	170,006	152,372
Gross Unrealized Gains	3,172	6,847
Gross Unrealized Losses	(2,284)	(15)
Available-for-sale Securities, Fair Value	170,894	159,204
Private labeled mortgage-backed pools [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	1,188	1,960
Gross Unrealized Gains	38	71
Gross Unrealized Losses
Available-for-sale Securities, Fair Value	1,226	2,031
Corporate notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available for sale investment securities, Amortized Cost	708	32
Gross Unrealized Gains	25	19
Gross Unrealized Losses
Available-for-sale Securities, Fair Value	$ 733	$ 51