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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Purchased Impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	$ 26,082	$ 55,149	$ 37,230	$ 42,252
Interest income	(4,149)	(10,428)	(15,583)	(28,879)
Reclassifications from nonaccretable balance, net	129	172	415	31,520
Other
Balance at end of period	22,062	44,893	22,062	44,893
Other [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	450,970	622,093	538,633	638,272
Interest income	(39,019)	(60,786)	(135,105)	(190,072)
Reclassifications from nonaccretable balance, net	9,673		10,448	122,519
Other	1,870	6,254	9,518	(3,158)
Balance at end of period	$ 423,494	$ 567,561	$ 423,494	$ 567,561