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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Purchased Impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	$ 33,728	$ 22,565	$ 42,252	$ 30,805
Interest income	(9,747)	(9,621)	(18,451)	(17,285)
Reclassifications from (to) nonaccretable balance, net	31,168	42,655	31,348	42,079
Other
Balance at end of period	55,149	55,599	55,149	55,599
Other [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	577,609	747,466	638,272	807,960
Interest income	(67,539)	(80,249)	(129,286)	(153,972)
Reclassifications from (to) nonaccretable balance, net	111,702	97,165	122,519	98,165
Other	321	(31,221)	(9,412)	(18,992)
Balance at end of period	$ 622,093	$ 733,161	$ 622,093	$ 733,161