Loans and Leases (Schedule of Changes in Accretable Discount Related to Credit Impaired Acquired Loans) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Changes In Accretable Discount [Line Items]
Balance - beginning of period	$ 58,817		$ 56,799		$ 62,868		$ 4,881
Tower acquisition	0		0		0		54,418
Accretion to interest income	(5,723)		(6,272)		(12,293)		(8,772)
Net reclassification (to) from non-accretable to accretable	(3,907)	[1]	0	[1]	(1,388)	[1]	0	[1]
Balance - end of period	$ 49,187		$ 50,527		$ 49,187		$ 50,527

[1] Resulting from decline in future interest earnings due to prepayments of performing loans.