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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Purchased impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	$ 55,149	$ 55,599	$ 42,252	$ 30,805
Interest income	(10,428)	(12,436)	(28,879)	(29,721)
Reclassifications from nonaccretable balance, net	172	542	31,520	42,621
Other
Balance at end of period	44,893	43,705	44,893	43,705
Other [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	622,093	733,161	638,272	807,960
Interest income	(60,786)	(74,936)	(190,072)	(228,908)
Reclassifications from nonaccretable balance, net			122,519	98,165
Other	6,254	1,382	(3,158)	(17,610)
Balance at end of period	$ 567,561	$ 659,607	$ 567,561	$ 659,607