Loans and Allowances for Credit Losses Part 3 (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	$ 10,170,974	$ 10,350,320	$ 9,686,140
Non-Graded, Recorded Investment	1,922,590	1,961,136	1,891,304
Total	12,093,564	12,311,456	11,577,444
Related Allowance [Abstract]
Internally Risk Graded, Allowance	121,611	127,322	157,753
Non-Graded, Allowance	41,542	43,998	42,106
Allowance For Financing Receivable Total	205,965	215,507	244,209	253,481
Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	9,963,687	10,111,255	9,353,153
Non-Graded, Recorded Investment	1,885,993	1,924,879	1,868,380
Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	111,251	140,912	172,552
Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	96,036	98,153	160,435
Non-Graded, Recorded Investment	36,597	36,257	22,924
Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,400,848	7,624,442	6,926,003
Non-Graded, Recorded Investment	17,457	17,470	17,582
Total	7,418,305	7,641,912	6,943,585
Related Allowance [Abstract]
Internally Risk Graded, Allowance	65,320	64,181	84,853
Non-Graded, Allowance	1,099	1,099	1,119
Allowance For Financing Receivable Total	66,419	65,280	85,972
Commercial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,319,106	7,533,757	6,781,307
Non-Graded, Recorded Investment	17,385	17,406	17,509
Commercial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	61,953	66,282	83,019
Commercial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	19,789	24,403	61,677
Non-Graded, Recorded Investment	72	64	73
Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Total	2,349,432	2,460,659	2,152,301
Commercial [Member] | Energy [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,342,500	2,448,954	2,142,978
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Energy [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,555	9,245	8,987
Commercial [Member] | Energy [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,377	2,460	336
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Total	2,114,799	2,164,186	1,951,021
Commercial [Member] | Services [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,074,198	2,119,734	1,899,082
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Services [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	31,127	32,362	39,049
Commercial [Member] | Services [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	9,474	12,090	12,890
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Total	1,085,000	1,106,439	997,174
Commercial [Member] | Wholesale/retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,071,954	1,093,413	958,682
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Wholesale/retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,807	9,949	23,104
Commercial [Member] | Wholesale/retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,239	3,077	15,388
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Total	399,818	348,484	341,706
Commercial [Member] | Manufacturing [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	387,346	337,132	308,187
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Manufacturing [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,624	9,345	10,117
Commercial [Member] | Manufacturing [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,848	2,007	23,402
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Integrated food services [Member]
Recorded Investment [Abstract]
Total	173,800	191,106	204,101
Commercial [Member] | Integrated food services [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	173,800	190,422	203,351
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Integrated food services [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	750
Commercial [Member] | Integrated food services [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	684	0
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Healthcare [Member]
Recorded Investment [Abstract]
Total	1,081,636	1,081,406	983,161
Commercial [Member] | Healthcare [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,078,550	1,077,773	974,209
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Healthcare [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	124	467	1,006
Commercial [Member] | Healthcare [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,962	3,166	7,946
Non-Graded, Recorded Investment	0	0	0
Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Total	213,820	289,632	314,121
Commercial [Member] | Other commercial and industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	190,758	266,329	294,818
Non-Graded, Recorded Investment	17,385	17,406	17,509
Commercial [Member] | Other commercial and industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,716	4,914	6
Commercial [Member] | Other commercial and industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	889	919	1,715
Non-Graded, Recorded Investment	72	64	73
Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,285,160	2,228,999	2,252,299
Non-Graded, Recorded Investment	0	0	0
Total	2,285,160	2,228,999	2,252,299
Related Allowance [Abstract]
Internally Risk Graded, Allowance	48,528	54,884	62,742
Non-Graded, Allowance	0	0	0
Allowance For Financing Receivable Total	48,528	54,884	62,742
Commercial Real Estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,178,491	2,105,105	2,092,662
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	41,494	63,268	73,162
Commercial Real Estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	65,175	60,626	86,475
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Construction and land development [Member]
Recorded Investment [Abstract]
Total	237,829	253,093	315,541
Commercial Real Estate [Member] | Construction and land development [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	194,944	204,010	234,687
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Construction and land development [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	19,423	22,952	28,438
Commercial Real Estate [Member] | Construction and land development [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	23,462	26,131	52,416
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Total	584,279	522,786	477,975
Commercial Real Estate [Member] | Retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	572,761	508,342	463,143
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,597	6,327	8,639
Commercial Real Estate [Member] | Retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	8,921	8,117	6,193
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Total	420,644	427,872	380,176
Commercial Real Estate [Member] | Office [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	401,070	405,763	357,006
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Office [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,723	15,280	12,437
Commercial Real Estate [Member] | Office [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	12,851	6,829	10,733
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Total	460,474	402,896	432,970
Commercial Real Estate [Member] | Multifamily [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	453,822	393,566	420,156
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Multifamily [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,151	6,624	9,400
Commercial Real Estate [Member] | Multifamily [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,501	2,706	3,414
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Total	237,049	245,994	286,919
Commercial Real Estate [Member] | Industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	234,590	241,761	286,642
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	261	265	277
Commercial Real Estate [Member] | Industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,198	3,968	0
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Total	344,885	376,358	358,718
Commercial Real Estate [Member] | Other commercial real estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	321,304	351,663	331,028
Non-Graded, Recorded Investment	0	0	0
Commercial Real Estate [Member] | Other commercial real estate [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,339	11,820	13,971
Commercial Real Estate [Member] | Other commercial real estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	13,242	12,875	13,719
Non-Graded, Recorded Investment	0	0	0
Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	247,814	265,503	298,139
Non-Graded, Recorded Investment	1,764,636	1,779,537	1,670,787
Total	2,012,450	2,045,040	1,968,926
Related Allowance [Abstract]
Internally Risk Graded, Allowance	4,600	5,270	7,482
Non-Graded, Allowance	35,622	36,433	34,146
Allowance For Financing Receivable Total	40,222	41,703	41,628
Residential Mortgage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	230,595	242,823	276,892
Non-Graded, Recorded Investment	1,729,874	1,745,338	1,650,837
Residential Mortgage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,555	10,271	13,735
Residential Mortgage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,664	12,409	7,512
Non-Graded, Recorded Investment	34,762	34,199	19,950
Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Total	1,091,575	1,123,965	1,138,439
Residential Mortgage [Member] | Permanent mortgage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	230,595	242,823	276,892
Non-Graded, Recorded Investment	816,272	831,008	824,990
Residential Mortgage [Member] | Permanent mortgage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,555	10,271	13,735
Residential Mortgage [Member] | Permanent mortgage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,664	12,409	7,512
Non-Graded, Recorded Investment	27,489	27,454	15,310
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Total	162,419	160,444	180,862
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Non-Graded, Recorded Investment	162,205	159,955	180,862
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Non-Graded, Recorded Investment	214	489	0
Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Total	758,456	760,631	649,625
Residential Mortgage [Member] | Home equity [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Non-Graded, Recorded Investment	751,397	754,375	644,985
Residential Mortgage [Member] | Home equity [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Residential Mortgage [Member] | Home equity [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Non-Graded, Recorded Investment	7,059	6,256	4,640
Consumer [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	237,152	231,376	209,699
Non-Graded, Recorded Investment	140,497	164,129	202,935
Total	377,649	395,505	412,634
Related Allowance [Abstract]
Internally Risk Graded, Allowance	3,163	2,987	2,676
Non-Graded, Allowance	4,821	6,466	6,841
Allowance For Financing Receivable Total	7,984	9,453	9,517
Consumer [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	235,495	229,570	202,292
Non-Graded, Recorded Investment	138,734	162,135	200,034
Consumer [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,249	1,091	2,636
Consumer [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	408	715	4,771
Non-Graded, Recorded Investment	1,763	1,994	2,901
Consumer [Member] | Indirect automobile [Member]
Recorded Investment [Abstract]
Total	24,368	34,735	81,524
Consumer [Member] | Indirect automobile [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Non-Graded, Recorded Investment	23,049	33,157	78,916
Consumer [Member] | Indirect automobile [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Consumer [Member] | Indirect automobile [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Non-Graded, Recorded Investment	1,319	1,578	2,608
Consumer [Member] | Other consumer [Member]
Recorded Investment [Abstract]
Total	353,281	360,770	331,110
Consumer [Member] | Other consumer [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	235,495	229,570	202,292
Non-Graded, Recorded Investment	115,685	128,978	121,118
Consumer [Member] | Other consumer [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,249	1,091	2,636
Consumer [Member] | Other consumer [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	408	715	4,771
Non-Graded, Recorded Investment	444	416	293
Allocated Class of Receivables [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,170,974	10,350,320	9,686,140
Non-Graded, Recorded Investment	1,922,590	1,961,136	1,891,304
Total	12,093,564	12,311,456	11,577,444
Related Allowance [Abstract]
Internally Risk Graded, Allowance	121,611	127,322	157,753
Non-Graded, Allowance	41,542	43,998	42,106
Allowance For Financing Receivable Total	163,153	171,320	199,859
Nonspecific allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0	0	0
Non-Graded, Recorded Investment	0	0	0
Total	0	0	0
Related Allowance [Abstract]
Internally Risk Graded, Allowance	0	0	0
Non-Graded, Allowance	0	0	0
Allowance For Financing Receivable Total	$ 42,812	$ 44,187	$ 44,350	$ 46,350