Loans and Allowances for Credit Losses Part 3 (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	$ 10,480,793		$ 10,350,320	$ 9,650,883
Non-Graded, Recorded Investment	1,959,989		1,961,136	1,925,548
Total	12,440,782		12,311,456	11,576,431
Related Allowance [Abstract]
Internally Risk Graded, Allowance	118,586		127,322	147,045
Non-Graded, Allowance	42,089		43,998	43,766
Allowance For Financing Receivable Total	203,124	205,965	215,507	231,669	244,209	253,481
Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,303,771		10,111,255	9,365,144
Non-Graded, Recorded Investment	1,924,100		1,924,879	1,907,383
Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	90,778		140,912	159,422
Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	86,244		98,153	126,317
Non-Graded, Recorded Investment	35,889		36,257	18,165
Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,689,954		7,624,442	7,017,925
Non-Graded, Recorded Investment	18,166		17,470	17,610
Total	7,708,120		7,641,912	7,035,535
Related Allowance [Abstract]
Internally Risk Graded, Allowance	62,830		64,181	82,357
Non-Graded, Allowance	1,214		1,099	1,120
Allowance For Financing Receivable Total	64,044		65,280	83,477
Commercial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,624,152		7,533,757	6,908,788
Non-Graded, Recorded Investment	18,105		17,406	17,510
Commercial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	44,994		66,282	74,708
Commercial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	20,808		24,403	34,429
Non-Graded, Recorded Investment	61		64	100
Commercial [Member] | Energy [Member]
Recorded Investment [Abstract]
Total	2,384,746		2,460,659	2,268,852
Commercial [Member] | Energy [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,378,187		2,448,954	2,254,806
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Energy [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,282		9,245	10,959
Commercial [Member] | Energy [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,277		2,460	3,087
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Services [Member]
Recorded Investment [Abstract]
Total	2,204,253		2,164,186	1,988,330
Commercial [Member] | Services [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,170,695		2,119,734	1,937,953
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Services [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	26,110		32,362	40,254
Commercial [Member] | Services [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,448		12,090	10,123
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Wholesale/retail [Member]
Recorded Investment [Abstract]
Total	1,175,543		1,106,439	946,684
Commercial [Member] | Wholesale/retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,167,215		1,093,413	930,912
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Wholesale/retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,628		9,949	11,597
Commercial [Member] | Wholesale/retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,700		3,077	4,175
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Manufacturing [Member]
Recorded Investment [Abstract]
Total	386,133		348,484	347,086
Commercial [Member] | Manufacturing [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	381,729		337,132	325,024
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Manufacturing [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,528		9,345	9,832
Commercial [Member] | Manufacturing [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	876		2,007	12,230
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Integrated food services [Member]
Recorded Investment [Abstract]
Total	163,551		191,106	206,269
Commercial [Member] | Integrated food services [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	158,674		190,422	205,573
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Integrated food services [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,877		0	696
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	1,118,810		1,081,406	984,340
Commercial [Member] | Healthcare [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,116,089		1,077,773	979,985
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Healthcare [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	51		467	1,045
Commercial [Member] | Healthcare [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,670		3,166	3,310
Non-Graded, Recorded Investment	0		0	0
Commercial [Member] | Other commercial and industrial [Member]
Recorded Investment [Abstract]
Total	275,084		289,632	293,974
Commercial [Member] | Other commercial and industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	251,563		266,329	274,535
Non-Graded, Recorded Investment	18,105		17,406	17,510
Commercial [Member] | Other commercial and industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,518		4,914	325
Commercial [Member] | Other commercial and industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	837		919	1,504
Non-Graded, Recorded Investment	61		64	100
Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,317,096		2,228,999	2,149,724
Non-Graded, Recorded Investment	0		0	6
Total	2,317,096		2,228,999	2,149,730
Related Allowance [Abstract]
Internally Risk Graded, Allowance	49,687		54,884	55,806
Non-Graded, Allowance	0		0	0
Allowance For Financing Receivable Total	49,687		54,884	55,806
Commercial Real Estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,218,338		2,105,105	2,001,253
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	40,065		63,268	68,263
Commercial Real Estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	58,693		60,626	80,208
Non-Graded, Recorded Investment	0		0	6
Commercial Real Estate [Member] | Construction and land development [Member]
Recorded Investment [Abstract]
Total	225,654		253,093	292,097
Commercial Real Estate [Member] | Construction and land development [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	184,216		204,010	219,301
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	20,303		22,952	26,746
Commercial Real Estate [Member] | Construction and land development [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	21,135		26,131	46,050
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Retail [Member]
Recorded Investment [Abstract]
Total	553,412		522,786	506,146
Commercial Real Estate [Member] | Retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	540,872		508,342	489,948
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,134		6,327	8,290
Commercial Real Estate [Member] | Retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	8,406		8,117	7,908
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Office [Member]
Recorded Investment [Abstract]
Total	459,558		427,872	395,339
Commercial Real Estate [Member] | Office [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	450,790		405,763	372,398
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Office [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	940		15,280	12,352
Commercial Real Estate [Member] | Office [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,828		6,829	10,589
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Multifamily [Member]
Recorded Investment [Abstract]
Total	500,452		402,896	358,416
Commercial Real Estate [Member] | Multifamily [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	491,864		393,566	348,520
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Multifamily [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,141		6,624	6,677
Commercial Real Estate [Member] | Multifamily [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,447		2,706	3,219
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Industrial [Member]
Recorded Investment [Abstract]
Total	253,990		245,994	228,725
Commercial Real Estate [Member] | Industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	253,732		241,761	228,452
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	258		265	273
Commercial Real Estate [Member] | Industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		3,968	0
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Other commercial real estate [Member]
Recorded Investment [Abstract]
Total	324,030		376,358	369,007
Commercial Real Estate [Member] | Other commercial real estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	296,864		351,663	342,634
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	12,289		11,820	13,925
Commercial Real Estate [Member] | Other commercial real estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	14,877		12,875	12,442
Non-Graded, Recorded Investment	0		0	6
Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	230,359		265,503	286,499
Non-Graded, Recorded Investment	1,809,426		1,779,537	1,716,386
Total	2,039,785		2,045,040	2,002,885
Related Allowance [Abstract]
Internally Risk Graded, Allowance	3,753		5,270	6,987
Non-Graded, Allowance	35,453		36,433	35,701
Allowance For Financing Receivable Total	39,206		41,703	42,688
Residential Mortgage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	219,222		242,823	265,891
Non-Graded, Recorded Investment	1,775,240		1,745,338	1,700,869
Residential Mortgage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,789		10,271	13,398
Residential Mortgage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,348		12,409	7,210
Non-Graded, Recorded Investment	34,186		34,199	15,517
Residential Mortgage [Member] | Permanent mortgage [Member]
Recorded Investment [Abstract]
Total	1,095,871		1,123,965	1,144,839
Residential Mortgage [Member] | Permanent mortgage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	219,222		242,823	265,891
Non-Graded, Recorded Investment	839,113		831,008	847,414
Residential Mortgage [Member] | Permanent mortgage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,789		10,271	13,398
Residential Mortgage [Member] | Permanent mortgage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,348		12,409	7,210
Non-Graded, Recorded Investment	26,399		27,454	10,926
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Recorded Investment [Abstract]
Total	156,887		160,444	162,240
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	156,804		159,955	162,240
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	83		489	0
Residential Mortgage [Member] | Home equity [Member]
Recorded Investment [Abstract]
Total	787,027		760,631	695,806
Residential Mortgage [Member] | Home equity [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	779,323		754,375	691,215
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	7,704		6,256	4,591
Consumer [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	243,384		231,376	196,735
Non-Graded, Recorded Investment	132,397		164,129	191,546
Total	375,781		395,505	388,281
Related Allowance [Abstract]
Internally Risk Graded, Allowance	2,316		2,987	1,895
Non-Graded, Allowance	5,422		6,466	6,945
Allowance For Financing Receivable Total	7,738		9,453	8,840
Consumer [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	242,059		229,570	189,212
Non-Graded, Recorded Investment	130,755		162,135	189,004
Consumer [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	930		1,091	3,053
Consumer [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	395		715	4,470
Non-Graded, Recorded Investment	1,642		1,994	2,542
Consumer [Member] | Indirect automobile [Member]
Recorded Investment [Abstract]
Total	16,555		34,735	62,938
Consumer [Member] | Indirect automobile [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	15,367		33,157	60,681
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	1,188		1,578	2,257
Consumer [Member] | Other consumer [Member]
Recorded Investment [Abstract]
Total	359,226		360,770	325,343
Consumer [Member] | Other consumer [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	242,059		229,570	189,212
Non-Graded, Recorded Investment	115,388		128,978	128,323
Consumer [Member] | Other consumer [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	930		1,091	3,053
Consumer [Member] | Other consumer [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	395		715	4,470
Non-Graded, Recorded Investment	454		416	285
Allocated Class of Receivables [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,480,793		10,350,320	9,650,883
Non-Graded, Recorded Investment	1,959,989		1,961,136	1,925,548
Total	12,440,782		12,311,456	11,576,431
Related Allowance [Abstract]
Internally Risk Graded, Allowance	118,586		127,322	147,045
Non-Graded, Allowance	42,089		43,998	43,766
Allowance For Financing Receivable Total	160,675		171,320	190,811
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	$ 42,449	$ 42,812	$ 44,187	$ 40,858	$ 44,350	$ 46,350