Securities - Amortized Cost and Fair Value of Securities Available for Sale and Held to Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized cost within one year	$ 4,449	$ 3,643
Amortized cost one to five years	43,451	49,198
Amortized cost for five to ten years	111,942	106,225
Amortized cost for after ten years	58,764	62,120
Total amortized cost	218,606	221,186
Total available for sale investment securities, Amortized Cost	514,839	508,427
Within one year, amortized cost	9,910	9,910
One to five years, amortized cost
Total held to maturity investment securities, amortized cost	9,910	9,910
Fair value within one year	4,486	3,663
Fair value for one to five years	43,959	49,627
Fair value for five to ten years	114,654	107,424
Fair value for after ten years	58,866	61,051
Total fair value	221,965	221,765
Investment securities, available for sale	519,430	508,591
Within one year, fair value	9,910	9,910
One to five years, fair value
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
Investment securities, available for sale	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
Investment securities, available for sale	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
Investment securities, available for sale	$ 1,056	$ 1,226