Loans and Leases (Allowance For Loan And Lease Losses By Portfolio Segment) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance, beginning of period				$ 194,320	$ 194,320			$ 174,990	$ 194,320	$ 174,990	$ 159,264
Provision (benefit) charged to expense	$ 13,000	$ 10,150	$ 7,250	10,500	12,500	$ 14,250	$ 14,000	15,600	40,900	56,350	49,300
Losses charged off									(44,927)	(46,912)	(43,560)
Recoveries									9,701	9,892	9,986
Balance, end of period	199,994			194,320	194,320	194,320		174,990	194,320	174,990	159,264	$ 194,320	$ 174,990
Individually evaluated for impairment	16,554					18,593							22,204
Collectively evaluated for impairment	183,440					175,727							152,786
Individually evaluated for impairment	246,753											249,355	279,171
Collectively evaluated for impairment	17,277,105											16,777,233	15,392,564
Total Loans and Leases	17,523,858											17,026,588	15,671,735
Residential Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance, beginning of period				23,226	23,226			25,876	23,226	25,876	25,452
Provision (benefit) charged to expense									(2,692)	230	6,057
Losses charged off									(2,500)	(4,636)	(6,508)
Recoveries									1,024	1,756	875
Balance, end of period	19,058			23,226	23,226	23,226		25,876	23,226	25,876	25,452	23,226	25,876
Individually evaluated for impairment	4,805					8,090							10,364
Collectively evaluated for impairment	14,253					15,136							15,512
Individually evaluated for impairment	114,295											119,424	134,448
Collectively evaluated for impairment	4,376,583											4,135,258	3,926,553
Total Loans and Leases	4,490,878											4,254,682	4,061,001
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance, beginning of period				45,233	45,233			42,052	45,233	42,052	43,518
Provision (benefit) charged to expense									9,367	18,507	11,847
Losses charged off									(24,447)	(20,669)	(17,679)
Recoveries									6,037	5,343	4,366
Balance, end of period	36,190			45,233	45,233	45,233		42,052	45,233	42,052	43,518	45,233	42,052
Individually evaluated for impairment	1,668					2,903							3,477
Collectively evaluated for impairment	34,522					42,330							38,575
Individually evaluated for impairment	45,436											45,719	48,425
Collectively evaluated for impairment	2,544,789											2,638,781	2,654,135
Total Loans and Leases	2,590,225											2,684,500	2,702,560
Commercial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance, beginning of period				71,905	71,905			59,977	71,905	59,977	47,068
Provision (benefit) charged to expense									23,417	28,662	21,693
Losses charged off									(8,147)	(18,360)	(11,522)
Recoveries									2,358	1,626	2,738
Balance, end of period	89,533			71,905	71,905	71,905		59,977	71,905	59,977	47,068	71,905	59,977
Individually evaluated for impairment	9,786					7,422							5,197
Collectively evaluated for impairment	79,747					64,483							54,780
Individually evaluated for impairment	72,471											53,037	56,581
Collectively evaluated for impairment	5,296,223											4,887,894	4,259,418
Total Loans and Leases	5,368,694											4,940,931	4,315,999
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance, beginning of period				47,477	47,477			41,598	47,477	41,598	37,148
Provision (benefit) charged to expense									11,040	7,930	11,381
Losses charged off									(9,275)	(2,682)	(7,578)
Recoveries									165	631	647
Balance, end of period	49,407			47,477	47,477	47,477		41,598	47,477	41,598	37,148	47,477	41,598
Individually evaluated for impairment	272					169							3,163
Collectively evaluated for impairment	49,135					47,308							38,435
Individually evaluated for impairment	11,226											24,755	39,295
Collectively evaluated for impairment	4,512,602											4,486,091	3,952,354
Total Loans and Leases	4,523,828											4,510,846	3,991,649
Finance Leases Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance, beginning of period				6,479	6,479			5,487	6,479	5,487	6,078
Provision (benefit) charged to expense									(232)	1,021	(1,678)
Losses charged off									(558)	(565)	(273)
Recoveries									117	536	1,360
Balance, end of period	5,806			$ 6,479	$ 6,479	6,479		$ 5,487	$ 6,479	$ 5,487	$ 6,078	6,479	5,487
Individually evaluated for impairment	23					9							3
Collectively evaluated for impairment	5,783					$ 6,470							5,484
Individually evaluated for impairment	3,325											6,420	422
Collectively evaluated for impairment	546,908											629,209	600,104
Total Loans and Leases	$ 550,233											$ 635,629	$ 600,526