Aggregate Activity in Allowance For Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Allowance Excluding Purchased Credit Impaired	Mar. 31, 2013 Allowance Excluding Purchased Credit Impaired	Mar. 31, 2014 Purchased Credit Impaired	Mar. 31, 2013 Purchased Credit Impaired	Dec. 31, 2012 Purchased Credit Impaired
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 24,077	$ 25,770	$ 23,322	$ 25,762	$ 755	$ 8	$ 8
Provision for loan losses	1,590	1,142	1,852	1,142	(262)
Benefit attributable to the FDIC indemnification asset	203				203
Provision for loan losses charged to operations	1,793	1,142	1,852	1,142	(59)
Provision for loan losses recorded through the FDIC indemnification asset	(203)				(203)
Charge-offs	(2,216)	(2,759)	(2,216)	(2,759)
Recoveries	347	697	347	697
Net charge-offs	(1,869)	(2,062)	(1,869)	(2,062)
Ending balance	$ 23,798	$ 24,850	$ 23,305	$ 24,842	$ 493	$ 8	$ 8