Unrealized Gross Losses and Estimated Fair values of Investment Securities by Length of Time that Individual Securities in Each Category in Continuous Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 19,401	$ 48,020
Unrealized Losses	(84)	(336)
Fair Value	10,132	14,853
Unrealized Losses	(1,614)	(2,770)
Fair Value	29,533	62,873
Unrealized Losses	(1,698)	(3,106)
Obligations of U.S. government sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Fair Value		9,995
Unrealized Losses		(5)
Fair Value		9,995
Unrealized Losses		(5)
Collateralized Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value	19,401	38,025
Unrealized Losses	(84)	(331)
Fair Value	38	66
Fair Value	19,439	38,091
Unrealized Losses	(84)	(331)
Private issue collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Fair Value	10,094	10,641
Unrealized Losses	(1,614)	(1,916)
Fair Value	10,094	10,641
Unrealized Losses	(1,614)	(1,916)
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value		4,146
Unrealized Losses		(854)
Fair Value		4,146
Unrealized Losses		$ (854)