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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	$ 92,253	$ 106,842	$ 96,922	$ 107,351
Other adjustments	(335)	(205)	(588)	(743)
Reclassification from (to) allowance for unfunded lending-related commitments	62	284	(102)	136
Charge-offs	(8,102)	(12,815)	(24,978)	(45,752)
Recoveries	1,113	1,502	3,620	4,116
Provision for credit losses	6,028	11,580	16,145	42,080
Allowance for loan losses at period end	91,019	107,188	91,019	107,188
Allowance for unfunded lending-related commitments at period end	822	1,267	822	1,267
Allowance for credit losses at period end	91,841	108,455	91,841	108,455
Allowance for credit losses at period end, Individually evaluated for impairment	6,660	14,975	6,660	14,975
Allowance for credit losses at period end, Collectively evaluated for impairment	84,962	93,259	84,962	93,259
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	219	221	219	221
Loans at period end, Individually evaluated for impairment	130,944	178,761	130,944	178,761
Loans at period end, Collectively evaluated for impairment	13,440,901	11,872,979	13,440,901	11,872,979
Loans at period end, Loans acquired with deteriorated credit quality	480,214	529,299	480,214	529,299
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	26,038	28,737	23,092	28,794
Other adjustments	(32)	(15)	(69)	(19)
Reclassification from (to) allowance for unfunded lending-related commitments	0	0	0	0
Charge-offs	(832)	(3,281)	(3,864)	(8,914)
Recoveries	296	756	883	1,319
Provision for credit losses	2,442	2,044	7,870	7,061
Allowance for loan losses at period end	27,912	28,241	27,912	28,241
Allowance for unfunded lending-related commitments at period end	0	0	0	0
Allowance for credit losses at period end	27,912	28,241	27,912	28,241
Allowance for credit losses at period end, Individually evaluated for impairment	2,296	5,498	2,296	5,498
Allowance for credit losses at period end, Collectively evaluated for impairment	25,427	22,636	25,427	22,636
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	189	107	189	107
Loans at period end, Individually evaluated for impairment	16,568	24,688	16,568	24,688
Loans at period end, Collectively evaluated for impairment	3,663,804	3,075,094	3,663,804	3,075,094
Loans at period end, Loans acquired with deteriorated credit quality	9,299	9,339	9,299	9,339
Commercial real-estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	40,702	51,950	48,658	52,135
Other adjustments	(265)	(193)	(482)	(621)
Reclassification from (to) allowance for unfunded lending-related commitments	62	284	(102)	136
Charge-offs	(4,510)	(6,982)	(11,354)	(25,228)
Recoveries	275	272	762	1,224
Provision for credit losses	2,395	5,488	1,177	23,173
Allowance for loan losses at period end	38,659	50,819	38,659	50,819
Allowance for unfunded lending-related commitments at period end	822	1,267	822	1,267
Allowance for credit losses at period end	39,481	52,086	39,481	52,086
Allowance for credit losses at period end, Individually evaluated for impairment	3,507	5,892	3,507	5,892
Allowance for credit losses at period end, Collectively evaluated for impairment	35,967	46,080	35,967	46,080
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	7	114	7	114
Loans at period end, Individually evaluated for impairment	89,201	124,401	89,201	124,401
Loans at period end, Collectively evaluated for impairment	4,360,556	3,963,310	4,360,556	3,963,310
Loans at period end, Loans acquired with deteriorated credit quality	60,618	58,399	60,618	58,399
Home equity
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	13,918	14,205	12,611	12,734
Other adjustments	(1)	0	(3)	0
Reclassification from (to) allowance for unfunded lending-related commitments	0	0	0	0
Charge-offs	(748)	(711)	(3,745)	(4,893)
Recoveries	99	43	478	376
Provision for credit losses	(308)	1,824	3,619	7,144
Allowance for loan losses at period end	12,960	15,361	12,960	15,361
Allowance for unfunded lending-related commitments at period end	0	0	0	0
Allowance for credit losses at period end	12,960	15,361	12,960	15,361
Allowance for credit losses at period end, Individually evaluated for impairment	292	2,447	292	2,447
Allowance for credit losses at period end, Collectively evaluated for impairment	12,668	12,914	12,668	12,914
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	0	0	0	0
Loans at period end, Individually evaluated for impairment	5,922	11,152	5,922	11,152
Loans at period end, Collectively evaluated for impairment	714,136	725,468	714,136	725,468
Loans at period end, Loans acquired with deteriorated credit quality	0	0	0	0
Residential real-estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	3,733	4,825	5,108	5,560
Other adjustments	(2)	(4)	(6)	(98)
Reclassification from (to) allowance for unfunded lending-related commitments	0	0	0	0
Charge-offs	(205)	(328)	(1,120)	(2,573)
Recoveries	111	64	316	87
Provision for credit losses	405	700	(256)	2,281
Allowance for loan losses at period end	4,042	5,257	4,042	5,257
Allowance for unfunded lending-related commitments at period end	0	0	0	0
Allowance for credit losses at period end	4,042	5,257	4,042	5,257
Allowance for credit losses at period end, Individually evaluated for impairment	512	886	512	886
Allowance for credit losses at period end, Collectively evaluated for impairment	3,530	4,371	3,530	4,371
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	0	0	0	0
Loans at period end, Individually evaluated for impairment	18,383	16,746	18,383	16,746
Loans at period end, Collectively evaluated for impairment	449,241	379,462	449,241	379,462
Loans at period end, Loans acquired with deteriorated credit quality	2,695	1,499	2,695	1,499
Premium finance receivables
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	6,309	5,268	5,583	6,096
Other adjustments	(35)	7	(28)	(5)
Reclassification from (to) allowance for unfunded lending-related commitments	0	0	0	0
Charge-offs	(1,557)	(1,297)	(4,259)	(3,671)
Recoveries	290	316	925	889
Provision for credit losses	1,260	1,193	4,046	2,178
Allowance for loan losses at period end	6,267	5,487	6,267	5,487
Allowance for unfunded lending-related commitments at period end	0	0	0	0
Allowance for credit losses at period end	6,267	5,487	6,267	5,487
Allowance for credit losses at period end, Individually evaluated for impairment	0	0	0	0
Allowance for credit losses at period end, Collectively evaluated for impairment	6,267	5,487	6,267	5,487
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	0	0	0	0
Loans at period end, Individually evaluated for impairment	0	0	0	0
Loans at period end, Collectively evaluated for impairment	4,104,695	3,560,337	4,104,695	3,560,337
Loans at period end, Loans acquired with deteriorated credit quality	407,602	459,883	407,602	459,883
Consumer and other
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses at beginning of period	1,553	1,857	1,870	2,032
Other adjustments	0	0	0	0
Reclassification from (to) allowance for unfunded lending-related commitments	0	0	0	0
Charge-offs	(250)	(216)	(636)	(473)
Recoveries	42	51	256	221
Provision for credit losses	(166)	331	(311)	243
Allowance for loan losses at period end	1,179	2,023	1,179	2,023
Allowance for unfunded lending-related commitments at period end	0	0	0	0
Allowance for credit losses at period end	1,179	2,023	1,179	2,023
Allowance for credit losses at period end, Individually evaluated for impairment	53	252	53	252
Allowance for credit losses at period end, Collectively evaluated for impairment	1,103	1,771	1,103	1,771
Allowance for credit losses at period end, Loans acquired with deteriorated credit quality	23	0	23	0
Loans at period end, Individually evaluated for impairment	870	1,774	870	1,774
Loans at period end, Collectively evaluated for impairment	148,469	169,308	148,469	169,308
Loans at period end, Loans acquired with deteriorated credit quality	$ 0	$ 179	$ 0	$ 179