Loans and Leases (Schedule of Changes in Accretable Discount Related to Purchased Credit Impaired Loans) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Balance - beginning of period	$ 50,527	$ 4,881
Tower acquisition	0	54,418
Accretion recognized during the period	(4,902)	(13,674)
Net reclassification from non-accretable to accretable	12,299	12,299
Balance - end of period	$ 57,924	$ 57,924