Investment Securities Available for Sale - Reconciliation of Available for Sale Securities in Continuous Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012 Securities	Dec. 31, 2011 Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	22	9
Less than 12 months, Fair value	$ 81,972	$ 23,024
Less than 12 months, Gross unrealized losses	736	192
12 months or longer, Number of securities	10	7
12 months or longer, Fair value	12,017	16,773
12 months or longer, Gross unrealized losses	110	198
Total number of securities	32	16
Total Fair value	93,989	39,797
Total Gross unrealized losses	846	390
State and municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	1
Less than 12 months, Fair value	1,091
Less than 12 months, Gross unrealized losses	1
12 months or longer, Number of securities
12 months or longer, Fair value
12 months or longer, Gross unrealized losses
Total number of securities	1
Total Fair value	1,091
Total Gross unrealized losses	1
Collateralized mortgage obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	12	9
Less than 12 months, Fair value	35,463	23,024
Less than 12 months, Gross unrealized losses	219	192
12 months or longer, Number of securities	10	7
12 months or longer, Fair value	12,017	16,773
12 months or longer, Gross unrealized losses	110	198
Total number of securities	22	16
Total Fair value	47,480	39,797
Total Gross unrealized losses	329	390
Other mortgage-backed (federal agencies) [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	1
Less than 12 months, Fair value	4,903
Less than 12 months, Gross unrealized losses	6
Total number of securities	1
Total Fair value	4,903
Total Gross unrealized losses	6
SBA Loan-Backed (Federal Agency) [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	8
Less than 12 months, Fair value	40,515
Less than 12 months, Gross unrealized losses	510
Total number of securities	8
Total Fair value	40,515
Total Gross unrealized losses	$ 510