Loans and Leases and the Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 970,496	$ 929,987	$ 955,992	$ 919,562
Provision for credit losses	47,000	44,000	128,000	112,000
Net charge-offs
Charge-offs	(59,275)	(53,141)	(164,857)	(133,579)
Recoveries	17,900	12,952	56,986	35,815
Net charge-offs	(41,375)	(40,189)	(107,871)	(97,764)
Ending balance	976,121	933,798	976,121	933,798
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	316,079	286,750	300,404	288,038
Provision for credit losses	26,222	21,507	39,667	32,686
Net charge-offs
Charge-offs	(21,075)	(26,912)	(34,711)	(46,990)
Recoveries	6,958	5,322	22,824	12,933
Net charge-offs	(14,117)	(21,590)	(11,887)	(34,057)
Ending balance	328,184	286,667	328,184	286,667
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	349,674	311,294	326,831	307,927
Provision for credit losses	9,963	1,879	29,799	13,769
Net charge-offs
Charge-offs	(1,564)	(2,203)	(3,569)	(12,352)
Recoveries	1,704	2,119	6,716	3,745
Net charge-offs	140	(84)	3,147	(8,607)
Ending balance	359,777	313,089	359,777	313,089
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	69,660	60,294	72,238	61,910
Provision for credit losses	(6,232)	(3,155)	(610)	(571)
Net charge-offs
Charge-offs	(6,754)	(3,268)	(18,816)	(9,695)
Recoveries	1,919	1,125	5,781	3,352
Net charge-offs	(4,835)	(2,143)	(13,035)	(6,343)
Ending balance	58,593	54,996	58,593	54,996
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	157,361	194,238	178,320	186,033
Provision for credit losses	16,539	24,448	59,113	65,038
Net charge-offs
Charge-offs	(29,882)	(20,758)	(107,761)	(64,542)
Recoveries	7,319	4,386	21,665	15,785
Net charge-offs	(22,563)	(16,372)	(86,096)	(48,757)
Ending balance	151,337	202,314	151,337	202,314
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	77,722	77,411	78,199	75,654
Provision for credit losses	508	(679)	31	1,078
Net charge-offs
Ending balance	$ 78,230	$ 76,732	$ 78,230	$ 76,732