Credit Quality Assessment (Summary Information on Allowance for Loan and Lease Loss Activity) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Credit Quality Assessment [Abstract]
Balance at beginning of year			$ 37,802	$ 38,766	$ 38,766
Provision (credit) for loan and lease losses	$ 1,218	$ 158	1,815	(824)
Loan and lease charge-offs			(1,837)	(1,176)	(2,687)
Loan and lease recoveries			933	1,193	1,886
Net charge-offs			(904)	17	(801)
Balance at period end	$ 38,713	$ 37,959	$ 38,713	$ 37,959	$ 37,802