Gross Unrealized Losses and Fair Value by Length of Time of Available-For-Sale Securities (Detail) (Available-for-Sale Securities, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Number of securities	15	7
Fair Value	$ 94,400	$ 46,404
Less than 12 months	508	231
More than 12 months	215	236
Total Unrealized Losses	723	467
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Number of securities		1
Fair Value		390
Less than 12 months		1
More than 12 months		0
Total Unrealized Losses		1
Mortgage-Backed
Schedule of Available-for-sale Securities [Line Items]
Number of securities	11	2
Fair Value	53,074	12,653
Less than 12 months	350	128
More than 12 months	0	0
Total Unrealized Losses	350	128
Corporate Debt
Schedule of Available-for-sale Securities [Line Items]
Number of securities		1
Fair Value		1,996
Less than 12 months		4
More than 12 months		0
Total Unrealized Losses		4
U.S. Government Agencies
Schedule of Available-for-sale Securities [Line Items]
Number of securities	3	2
Fair Value	39,840	29,900
Less than 12 months	158	98
More than 12 months	0	0
Total Unrealized Losses	158	98
Trust Preferred
Schedule of Available-for-sale Securities [Line Items]
Number of securities	1	1
Fair Value	1,486	1,465
Less than 12 months	0	0
More than 12 months	215	236
Total Unrealized Losses	$ 215	$ 236