Investment Securities - Age of Unrealized Losses and Fair Value of Related Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	$ 124,360	$ 85,657
Less than Twelve Months, Unrealized Losses	(760)	(1,087)
More than Twelve Months, Fair Value	48,802	63,222
More than Twelve Months, Unrealized Losses	(14,570)	(23,552)
Total, Fair Value	173,162	148,879
Total, Unrealized Losses	(15,330)	(24,639)
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	15,518	1,854
Less than Twelve Months, Unrealized Losses	(197)	(13)
More than Twelve Months, Fair Value		50
More than Twelve Months, Unrealized Losses		(1)
Total, Fair Value	15,518	1,904
Total, Unrealized Losses	(197)	(14)
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	80,152	33,520
Less than Twelve Months, Unrealized Losses	(355)	(152)
More than Twelve Months, Fair Value
More than Twelve Months, Unrealized Losses
Total, Fair Value	80,152	33,520
Total, Unrealized Losses	(355)	(152)
Trust preferred securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	28,690	35,527
Less than Twelve Months, Unrealized Losses	(208)	(730)
More than Twelve Months, Fair Value	48,802	55,612
More than Twelve Months, Unrealized Losses	(14,570)	(22,137)
Total, Fair Value	77,492	91,139
Total, Unrealized Losses	(14,778)	(22,867)
Corporate and other debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value		14,756
Less than Twelve Months, Unrealized Losses		(192)
More than Twelve Months, Fair Value		7,560
More than Twelve Months, Unrealized Losses		(1,414)
Total, Fair Value		22,316
Total, Unrealized Losses		$ (1,606)