Investment Securities Available for Sale - Reconciliation of Available for Sale Securities in Continuous Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013 Securities	Dec. 31, 2012 Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	28	16
Less than 12 months, Fair value	$ 92,701	$ 63,002
Less than 12 months, Gross unrealized losses	1,560	564
12 months or longer, Number of securities	8	9
12 months or longer, Fair value	5,707	9,547
12 months or longer, Gross unrealized losses	34	46
Total number of securities	36	25
Total Fair value	98,408	72,549
Total Gross unrealized losses	1,594	610
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	1,087
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	1,087
Total Gross unrealized losses	1
Collateralized mortgage obligations (federal agencies) [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	18	7
Less than 12 months, Fair value	62,043	23,301
Less than 12 months, Gross unrealized losses	1,080	109
12 months or longer, Number of securities	8	9
12 months or longer, Fair value	5,707	9,547
12 months or longer, Gross unrealized losses	34	46
Total number of securities	26	16
Total Fair value	67,750	32,848
Total Gross unrealized losses	1,114	155
Other mortgage-backed (federal agencies) [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	2	3
Less than 12 months, Fair value	5,646	14,586
Less than 12 months, Gross unrealized losses	72	92
12 months or longer, Number of securities
12 months or longer, Fair value
12 months or longer, Gross unrealized losses
Total number of securities	2	3
Total Fair value	5,646	14,586
Total Gross unrealized losses	72	92
SBA Loan-Backed (Federal Agency) [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Number of securities	7	6
Less than 12 months, Fair value	23,925	25,115
Less than 12 months, Gross unrealized losses	407	363
12 months or longer, Number of securities
12 months or longer, Fair value
12 months or longer, Gross unrealized losses
Total number of securities	7	6
Total Fair value	23,925	25,115
Total Gross unrealized losses	$ 407	$ 363