Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary Of Activity In Allowance For Credit Losses) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	$ 96,922	$ 107,351
Other adjustments	(148)	(229)
Reclassification from (to) allowance for unfunded lending-related commitments	(18)	(213)
Charge-offs	(9,017)	(13,161)
Recoveries	1,232	1,233
Provision for credit losses	3,304	15,367
Allowance for loan losses at period end	92,275	110,348
Allowance for unfunded lending-related commitments at period end	737	15,287
Allowance for credit losses at period end	93,012	125,635
Allowance for credit losses at period end, Individually evaluated for impairment	8,294	29,273
Allowance for credit losses at period end, Collectively evaluated for impairment	84,559	96,155
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	159	207
Loans at period end, Individually evaluated for impairment	144,985	203,554
Loans at period end, Collectively evaluated for impairment	12,485,216	11,133,896
Loans at period end, Loans acquired with deteriorated credit quality	502,959	562,862
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	23,092	28,794
Other adjustments	(15)	(3)
Reclassification from (to) allowance for unfunded lending-related commitments	0	0
Charge-offs	(648)	(4,540)
Recoveries	317	295
Provision for credit losses	1,943	4,406
Allowance for loan losses at period end	24,689	28,952
Allowance for unfunded lending-related commitments at period end	0	0
Allowance for credit losses at period end	24,689	28,952
Allowance for credit losses at period end, Individually evaluated for impairment	3,107	3,682
Allowance for credit losses at period end, Collectively evaluated for impairment	21,512	25,270
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	70	0
Loans at period end, Individually evaluated for impairment	18,350	27,447
Loans at period end, Collectively evaluated for impairment	3,410,011	2,840,405
Loans at period end, Loans acquired with deteriorated credit quality	10,836	4,843
Commercial real-estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	48,658	52,135
Other adjustments	(121)	(217)
Reclassification from (to) allowance for unfunded lending-related commitments	(18)	(213)
Charge-offs	(4,493)	(3,299)
Recoveries	145	368
Provision for credit losses	434	7,634
Allowance for loan losses at period end	44,605	56,408
Allowance for unfunded lending-related commitments at period end	737	15,287
Allowance for credit losses at period end	45,342	71,695
Allowance for credit losses at period end, Individually evaluated for impairment	4,041	23,089
Allowance for credit losses at period end, Collectively evaluated for impairment	41,301	48,409
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	0	197
Loans at period end, Individually evaluated for impairment	99,480	145,203
Loans at period end, Collectively evaluated for impairment	4,087,171	3,790,445
Loans at period end, Loans acquired with deteriorated credit quality	75,604	54,817
Home equity
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	12,611	12,734
Other adjustments	(1)	0
Reclassification from (to) allowance for unfunded lending-related commitments	0	0
Charge-offs	(2,267)	(2,397)
Recoveries	257	162
Provision for credit losses	366	1,623
Allowance for loan losses at period end	10,966	12,122
Allowance for unfunded lending-related commitments at period end	0	0
Allowance for credit losses at period end	10,966	12,122
Allowance for credit losses at period end, Individually evaluated for impairment	596	1,748
Allowance for credit losses at period end, Collectively evaluated for impairment	10,370	10,374
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	0	0
Loans at period end, Individually evaluated for impairment	7,537	16,057
Loans at period end, Collectively evaluated for impairment	700,211	743,161
Loans at period end, Loans acquired with deteriorated credit quality	0	0
Residential real-estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	5,108	5,560
Other adjustments	(2)	(9)
Reclassification from (to) allowance for unfunded lending-related commitments	0	0
Charge-offs	(226)	(1,728)
Recoveries	131	5
Provision for credit losses	(320)	1,312
Allowance for loan losses at period end	4,691	5,140
Allowance for unfunded lending-related commitments at period end	0	0
Allowance for credit losses at period end	4,691	5,140
Allowance for credit losses at period end, Individually evaluated for impairment	455	598
Allowance for credit losses at period end, Collectively evaluated for impairment	4,147	4,532
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	89	10
Loans at period end, Individually evaluated for impairment	18,026	12,984
Loans at period end, Collectively evaluated for impairment	405,668	346,835
Loans at period end, Loans acquired with deteriorated credit quality	3,075	833
Premium finance receivables
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	5,583	6,096
Other adjustments	(9)	0
Reclassification from (to) allowance for unfunded lending-related commitments	0	0
Charge-offs	(1,210)	(1,068)
Recoveries	321	294
Provision for credit losses	897	749
Allowance for loan losses at period end	5,582	6,071
Allowance for unfunded lending-related commitments at period end	0	0
Allowance for credit losses at period end	5,582	6,071
Allowance for credit losses at period end, Individually evaluated for impairment	0	0
Allowance for credit losses at period end, Collectively evaluated for impairment	5,582	6,071
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	0	0
Loans at period end, Individually evaluated for impairment	0	0
Loans at period end, Collectively evaluated for impairment	3,724,493	3,250,941
Loans at period end, Loans acquired with deteriorated credit quality	413,202	499,731
Consumer and other
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	1,870	2,032
Other adjustments	0	0
Reclassification from (to) allowance for unfunded lending-related commitments	0	0
Charge-offs	(173)	(129)
Recoveries	61	109
Provision for credit losses	(16)	(357)
Allowance for loan losses at period end	1,742	1,655
Allowance for unfunded lending-related commitments at period end	0	0
Allowance for credit losses at period end	1,742	1,655
Allowance for credit losses at period end, Individually evaluated for impairment	95	156
Allowance for credit losses at period end, Collectively evaluated for impairment	1,647	1,499
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	0	0
Loans at period end, Individually evaluated for impairment	1,592	1,863
Loans at period end, Collectively evaluated for impairment	157,662	162,109
Loans at period end, Loans acquired with deteriorated credit quality	$ 242	$ 2,638