Loans and Leases and the Allowance for Credit Losses - Summary of Changes in Accretable Yield for Acquired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	$ 575,863	$ 680,524
Interest income	(58,961)	(70,451)
Reclassifications from nonaccretable balance, net	37	10,997
Other	(838)	(9,733)
Balance at end of period	516,101	611,337
Purchased impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	37,230	42,252
Interest income	(6,328)	(8,704)
Reclassifications from nonaccretable balance, net	37	180
Other
Balance at end of period	30,939	33,728
Other [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	538,633	638,272
Interest income	(52,633)	(61,747)
Reclassifications from nonaccretable balance, net		10,817
Other	(838)	(9,733)
Balance at end of period	$ 485,162	$ 577,609