Loans, Allowance for Loan Losses, and Credit Quality Loans by Past Due Status (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summarized details of Loans
30-59 Days Past Due	$ 39,373	$ 43,388
60-89 Days Past Due	22,705	33,281
90 Days or More Past Due	64,922	86,863
Total Past Due	127,000	163,532
Current	17,466,846	15,732,729
Total loans	17,593,846	15,896,261
Percent of current nonaccrual loans	54.00%	42.00%
Commercial And Industrial Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	5,338	4,388
60-89 Days Past Due	10,908	5,200
90 Days or More Past Due	10,408	10,964
Total Past Due	26,654	20,552
Current	5,879,248	4,802,128
Total loans	5,905,902	4,822,680
Commercial Real Estate Owner Occupied Portfolio [Member]
Summarized details of Loans
30-59 Days Past Due	11,626	3,497
60-89 Days Past Due	2,240	3,815
90 Days or More Past Due	8,596	11,125
Total Past Due	22,462	18,437
Current	985,475	1,096,278
Total loans	1,007,937	1,114,715
Finance Leases Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or More Past Due	513	69
Total Past Due	513	69
Current	51,016	55,414
Total loans	51,529	55,483
Commercial And Business Lending [Member]
Summarized details of Loans
30-59 Days Past Due	16,964	7,885
60-89 Days Past Due	13,148	9,015
90 Days or More Past Due	19,517	22,158
Total Past Due	49,629	39,058
Current	6,915,739	5,953,820
Total loans	6,965,368	5,992,878
Commercial Real Estate Investor Portfolio Segment [Member]
Summarized details of Loans
30-59 Days Past Due	2,569	12,489
60-89 Days Past Due	955	15,033
90 Days or More Past Due	12,765	20,466
Total Past Due	16,289	47,988
Current	3,040,196	2,891,468
Total loans	3,056,485	2,939,456
Commercial Real Estate Construction Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	1,038	3,212
60-89 Days Past Due	106	1,118
90 Days or More Past Due	798	2,267
Total Past Due	1,942	6,597
Current	1,007,014	889,651
Total loans	1,008,956	896,248
Commercial Real Estate Lending [Member]
Summarized details of Loans
30-59 Days Past Due	3,607	15,701
60-89 Days Past Due	1,061	16,151
90 Days or More Past Due	13,563	22,733
Total Past Due	18,231	54,585
Current	4,047,210	3,781,119
Total loans	4,065,441	3,835,704
Commercial Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	20,571	23,586
60-89 Days Past Due	14,209	25,166
90 Days or More Past Due	33,080	44,891
Total Past Due	67,860	93,643
Current	10,962,949	9,734,939
Total loans	11,030,809	9,828,582
Home Equity [Member]
Summarized details of Loans
30-59 Days Past Due	9,652	10,336
60-89 Days Past Due	4,852	3,704
90 Days or More Past Due	10,654	14,677
Total Past Due	25,158	28,717
Current	1,610,900	1,796,297
Total loans	1,636,058	1,825,014
Installment and Credit Cards [Member]
Summarized details of Loans
30-59 Days Past Due	1,282	1,014
60-89 Days Past Due	785	289
90 Days or More Past Due	1,458	926
Total Past Due	3,525	2,229
Current	450,694	404,845
Total loans	454,219	407,074
Residential, Prime, Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	7,868	8,452
60-89 Days Past Due	2,859	4,122
90 Days or More Past Due	19,730	26,369
Total Past Due	30,457	38,943
Current	4,442,303	3,796,648
Total loans	4,472,760	3,835,591
Consumer Loan [Member]
Summarized details of Loans
30-59 Days Past Due	18,802	19,802
60-89 Days Past Due	8,496	8,115
90 Days or More Past Due	31,842	41,972
Total Past Due	59,140	69,889
Current	6,503,897	5,997,790
Total loans	6,563,037	6,067,679
Accruing Loans [Member]
Summarized details of Loans
30-59 Days Past Due	26,621	29,071
60-89 Days Past Due	16,507	23,978
90 Days or More Past Due	1,623	2,350
Total Past Due	44,751	55,399
Current	17,371,682	15,655,434
Total loans	17,416,433	15,710,833
Accruing Loans [Member] | Commercial And Industrial Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	4,466	3,390
60-89 Days Past Due	10,281	3,436
90 Days or More Past Due	254	1,199
Total Past Due	15,001	8,025
Current	5,841,238	4,776,936
Total loans	5,856,239	4,784,961
Accruing Loans [Member] | Commercial Real Estate Owner Occupied Portfolio [Member]
Summarized details of Loans
30-59 Days Past Due	8,429	1,015
60-89 Days Past Due	2,199	2,091
90 Days or More Past Due	0	0
Total Past Due	10,628	3,106
Current	971,484	1,081,945
Total loans	982,112	1,085,051
Accruing Loans [Member] | Finance Leases Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or More Past Due	0	0
Total Past Due	0	0
Current	49,728	55,414
Total loans	49,728	55,414
Accruing Loans [Member] | Commercial And Business Lending [Member]
Summarized details of Loans
30-59 Days Past Due	12,895	4,405
60-89 Days Past Due	12,480	5,527
90 Days or More Past Due	254	1,199
Total Past Due	25,629	11,131
Current	6,862,450	5,914,295
Total loans	6,888,079	5,925,426
Accruing Loans [Member] | Commercial Real Estate Investor Portfolio Segment [Member]
Summarized details of Loans
30-59 Days Past Due	712	9,081
60-89 Days Past Due	496	14,134
90 Days or More Past Due	0	0
Total Past Due	1,208	23,215
Current	3,032,592	2,878,645
Total loans	3,033,800	2,901,860
Accruing Loans [Member] | Commercial Real Estate Construction Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	951	836
60-89 Days Past Due	33	1,118
90 Days or More Past Due	0	0
Total Past Due	984	1,954
Current	1,002,573	887,827
Total loans	1,003,557	889,781
Accruing Loans [Member] | Commercial Real Estate Lending [Member]
Summarized details of Loans
30-59 Days Past Due	1,663	9,917
60-89 Days Past Due	529	15,252
90 Days or More Past Due	0	0
Total Past Due	2,192	25,169
Current	4,035,165	3,766,472
Total loans	4,037,357	3,791,641
Accruing Loans [Member] | Commercial Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	14,558	14,322
60-89 Days Past Due	13,009	20,779
90 Days or More Past Due	254	1,199
Total Past Due	27,821	36,300
Current	10,897,615	9,680,767
Total loans	10,925,436	9,717,067
Accruing Loans [Member] | Home Equity [Member]
Summarized details of Loans
30-59 Days Past Due	8,037	8,611
60-89 Days Past Due	2,546	2,069
90 Days or More Past Due	52	346
Total Past Due	10,635	11,026
Current	1,603,682	1,788,821
Total loans	1,614,317	1,799,847
Accruing Loans [Member] | Installment and Credit Cards [Member]
Summarized details of Loans
30-59 Days Past Due	1,186	885
60-89 Days Past Due	746	265
90 Days or More Past Due	1,317	637
Total Past Due	3,249	1,787
Current	450,357	404,173
Total loans	453,606	405,960
Accruing Loans [Member] | Residential, Prime, Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	2,840	5,253
60-89 Days Past Due	206	865
90 Days or More Past Due	0	168
Total Past Due	3,046	6,286
Current	4,420,028	3,781,673
Total loans	4,423,074	3,787,959
Accruing Loans [Member] | Consumer Loan [Member]
Summarized details of Loans
30-59 Days Past Due	12,063	14,749
60-89 Days Past Due	3,498	3,199
90 Days or More Past Due	1,369	1,151
Total Past Due	16,930	19,099
Current	6,474,067	5,974,667
Total loans	6,490,997	5,993,766
Nonaccrual Loan [Member]
Summarized details of Loans
30-59 Days Past Due	12,752	14,317
60-89 Days Past Due	6,198	9,303
90 Days or More Past Due	63,299	84,513
Total Past Due	82,249	108,133
Current	95,164	77,295
Total loans	177,413	185,428
Nonaccrual Loan [Member] | Commercial And Industrial Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	872	998
60-89 Days Past Due	627	1,764
90 Days or More Past Due	10,154	9,765
Total Past Due	11,653	12,527
Current	38,010	25,192
Total loans	49,663	37,719
Nonaccrual Loan [Member] | Commercial Real Estate Owner Occupied Portfolio [Member]
Summarized details of Loans
30-59 Days Past Due	3,197	2,482
60-89 Days Past Due	41	1,724
90 Days or More Past Due	8,596	11,125
Total Past Due	11,834	15,331
Current	13,991	14,333
Total loans	25,825	29,664
Nonaccrual Loan [Member] | Finance Leases Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days or More Past Due	513	69
Total Past Due	513	69
Current	1,288	0
Total loans	1,801	69
Nonaccrual Loan [Member] | Commercial And Business Lending [Member]
Summarized details of Loans
30-59 Days Past Due	4,069	3,480
60-89 Days Past Due	668	3,488
90 Days or More Past Due	19,263	20,959
Total Past Due	24,000	27,927
Current	53,289	39,525
Total loans	77,289	67,452
Nonaccrual Loan [Member] | Commercial Real Estate Investor Portfolio Segment [Member]
Summarized details of Loans
30-59 Days Past Due	1,857	3,408
60-89 Days Past Due	459	899
90 Days or More Past Due	12,765	20,466
Total Past Due	15,081	24,773
Current	7,604	12,823
Total loans	22,685	37,596
Nonaccrual Loan [Member] | Commercial Real Estate Construction Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	87	2,376
60-89 Days Past Due	73	0
90 Days or More Past Due	798	2,267
Total Past Due	958	4,643
Current	4,441	1,824
Total loans	5,399	6,467
Nonaccrual Loan [Member] | Commercial Real Estate Lending [Member]
Summarized details of Loans
30-59 Days Past Due	1,944	5,784
60-89 Days Past Due	532	899
90 Days or More Past Due	13,563	22,733
Total Past Due	16,039	29,416
Current	12,045	14,647
Total loans	28,084	44,063
Nonaccrual Loan [Member] | Commercial Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	6,013	9,264
60-89 Days Past Due	1,200	4,387
90 Days or More Past Due	32,826	43,692
Total Past Due	40,039	57,343
Current	65,334	54,172
Total loans	105,373	111,515
Nonaccrual Loan [Member] | Home Equity [Member]
Summarized details of Loans
30-59 Days Past Due	1,615	1,725
60-89 Days Past Due	2,306	1,635
90 Days or More Past Due	10,602	14,331
Total Past Due	14,523	17,691
Current	7,218	7,476
Total loans	21,741	25,167
Nonaccrual Loan [Member] | Installment and Credit Cards [Member]
Summarized details of Loans
30-59 Days Past Due	96	129
60-89 Days Past Due	39	24
90 Days or More Past Due	141	289
Total Past Due	276	442
Current	337	672
Total loans	613	1,114
Nonaccrual Loan [Member] | Residential, Prime, Financing Receivable [Member]
Summarized details of Loans
30-59 Days Past Due	5,028	3,199
60-89 Days Past Due	2,653	3,257
90 Days or More Past Due	19,730	26,201
Total Past Due	27,411	32,657
Current	22,275	14,975
Total loans	49,686	47,632
Nonaccrual Loan [Member] | Consumer Loan [Member]
Summarized details of Loans
30-59 Days Past Due	6,739	5,053
60-89 Days Past Due	4,998	4,916
90 Days or More Past Due	30,473	40,821
Total Past Due	42,210	50,790
Current	29,830	23,123
Total loans	$ 72,040	$ 73,913