Loans and Allowances for Credit Losses Part 7 (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Financing receivable, recorded investment, aging [Abstract]
Current	$ 12,160,578	$ 12,014,834	$ 11,245,244
Past due 30 to 89 days	38,805	37,938	58,888
Past due 90 days or more	119,266	124,274	127,817
Nonaccrual	122,133	134,410	144,482
Total	12,440,782	12,311,456	11,576,431
Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	7,681,836	7,611,023	6,987,698
Past due 30 to 89 days	2,974	5,994	13,171
Past due 90 days or more	2,441	428	137
Nonaccrual	20,869	24,467	34,529
Total	7,708,120	7,641,912	7,035,535
Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,382,377	2,454,928	2,263,505
Past due 30 to 89 days	92	3,071	2,260
Past due 90 days or more	0	200	0
Nonaccrual	2,277	2,460	3,087
Total	2,384,746	2,460,659	2,268,852
Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,192,771	2,150,386	1,974,465
Past due 30 to 89 days	1,769	1,710	3,705
Past due 90 days or more	2,265	0	37
Nonaccrual	7,448	12,090	10,123
Total	2,204,253	2,164,186	1,988,330
Commercial [Member] | Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,168,686	1,103,307	940,975
Past due 30 to 89 days	0	5	1,534
Past due 90 days or more	157	50	0
Nonaccrual	6,700	3,077	4,175
Total	1,175,543	1,106,439	946,684
Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	385,257	346,442	334,856
Past due 30 to 89 days	0	35	0
Past due 90 days or more	0	0	0
Nonaccrual	876	2,007	12,230
Total	386,133	348,484	347,086
Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,115,187	1,077,022	980,750
Past due 30 to 89 days	953	1,040	180
Past due 90 days or more	0	178	100
Nonaccrual	2,670	3,166	3,310
Total	1,118,810	1,081,406	984,340
Commercial [Member] | Integrated food services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	163,551	190,416	201,366
Past due 30 to 89 days	0	6	4,903
Past due 90 days or more	0	0	0
Nonaccrual	0	684	0
Total	163,551	191,106	206,269
Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	274,007	288,522	291,781
Past due 30 to 89 days	160	127	589
Past due 90 days or more	19	0	0
Nonaccrual	898	983	1,604
Total	275,084	289,632	293,974
Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,253,864	2,159,287	2,058,102
Past due 30 to 89 days	4,539	5,657	11,414
Past due 90 days or more	0	3,429	0
Nonaccrual	58,693	60,626	80,214
Total	2,317,096	2,228,999	2,149,730
Commercial Real Estate [Member] | Construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	204,519	226,962	245,246
Past due 30 to 89 days	0	0	801
Past due 90 days or more	0	0	0
Nonaccrual	21,135	26,131	46,050
Total	225,654	253,093	292,097
Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	542,946	514,252	492,612
Past due 30 to 89 days	2,060	349	5,626
Past due 90 days or more	0	68	0
Nonaccrual	8,406	8,117	7,908
Total	553,412	522,786	506,146
Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	451,730	417,866	384,225
Past due 30 to 89 days	0	3,177	525
Past due 90 days or more	0	0	0
Nonaccrual	7,828	6,829	10,589
Total	459,558	427,872	395,339
Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	492,306	400,151	354,455
Past due 30 to 89 days	1,699	39	742
Past due 90 days or more	0	0	0
Nonaccrual	6,447	2,706	3,219
Total	500,452	402,896	358,416
Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	253,990	242,026	228,333
Past due 30 to 89 days	0	0	392
Past due 90 days or more	0	0	0
Nonaccrual	0	3,968	0
Total	253,990	245,994	228,725
Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	308,373	358,030	353,231
Past due 30 to 89 days	780	2,092	3,328
Past due 90 days or more	0	3,361	0
Nonaccrual	14,877	12,875	12,448
Total	324,030	376,358	369,007
Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,853,635	1,854,347	1,820,679
Past due 30 to 89 days	28,810	23,687	31,814
Past due 90 days or more	116,806	120,398	127,665
Nonaccrual	40,534	46,608	22,727
Total	2,039,785	2,045,040	2,002,885
Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,054,435	1,075,687	1,111,078
Past due 30 to 89 days	8,689	8,366	15,130
Past due 90 days or more	0	49	495
Nonaccrual	32,747	39,863	18,136
Total	1,095,871	1,123,965	1,144,839
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	22,328	26,560	20,641
Past due 30 to 89 days	17,670	13,046	14,473
Past due 90 days or more	116,806	120,349	127,126
Nonaccrual	83	489	0
Total	156,887	160,444	162,240
Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	776,872	752,100	688,960
Past due 30 to 89 days	2,451	2,275	2,211
Past due 90 days or more	0	0	44
Nonaccrual	7,704	6,256	4,591
Total	787,027	760,631	695,806
Consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	371,243	390,177	378,765
Past due 30 to 89 days	2,482	2,600	2,489
Past due 90 days or more	19	19	15
Nonaccrual	2,037	2,709	7,012
Total	375,781	395,505	388,281
Consumer [Member] | Indirect automobile [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	14,827	31,869	58,909
Past due 30 to 89 days	540	1,273	1,771
Past due 90 days or more	0	15	1
Nonaccrual	1,188	1,578	2,257
Total	16,555	34,735	62,938
Consumer [Member] | Other consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	356,416	358,308	319,856
Past due 30 to 89 days	1,942	1,327	718
Past due 90 days or more	19	4	14
Nonaccrual	849	1,131	4,755
Total	$ 359,226	$ 360,770	$ 325,343