Loans and Leases and the Allowance for Credit Losses - Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 962,752	$ 921,373	$ 955,992	$ 919,562
Provision for credit losses	32,000	30,000	81,000	68,000
Net charge-offs
Charge-offs	(46,870)	(32,962)	(105,582)	(80,438)
Recoveries	22,614	11,576	39,086	22,863
Net charge-offs	(24,256)	(21,386)	(66,496)	(57,575)
Ending balance	970,496	929,987	970,496	929,987
Commercial, Financial, Leasing, etc. [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	323,866	281,069	300,404	288,038
Provision for credit losses	(10,919)	9,737	13,445	11,179
Net charge-offs
Charge-offs	(7,487)	(7,728)	(13,636)	(20,078)
Recoveries	10,619	3,672	15,866	7,611
Net charge-offs	3,132	(4,056)	2,230	(12,467)
Ending balance	316,079	286,750	316,079	286,750
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	331,985	317,375	326,831	307,927
Provision for credit losses	15,823	(3,652)	19,836	11,890
Net charge-offs
Charge-offs	(733)	(3,470)	(2,005)	(10,149)
Recoveries	2,599	1,041	5,012	1,626
Net charge-offs	1,866	(2,429)	3,007	(8,523)
Ending balance	349,674	311,294	349,674	311,294
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	68,371	60,741	72,238	61,910
Provision for credit losses	4,404	1,624	5,622	2,584
Net charge-offs
Charge-offs	(5,090)	(3,309)	(12,062)	(6,427)
Recoveries	1,975	1,238	3,862	2,227
Net charge-offs	(3,115)	(2,071)	(8,200)	(4,200)
Ending balance	69,660	60,294	69,660	60,294
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	160,819	186,052	178,320	186,033
Provision for credit losses	22,681	21,016	42,574	40,590
Net charge-offs
Charge-offs	(33,560)	(18,455)	(77,879)	(43,784)
Recoveries	7,421	5,625	14,346	11,399
Net charge-offs	(26,139)	(12,830)	(63,533)	(32,385)
Ending balance	157,361	194,238	157,361	194,238
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	77,711	76,136	78,199	75,654
Provision for credit losses	11	1,275	(477)	1,757
Net charge-offs
Ending balance	$ 77,722	$ 77,411	$ 77,722	$ 77,411