Loans and Allowances for Credit Losses Part 7 (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Financing receivable, recorded investment, aging [Abstract]
Current	$ 11,799,899	$ 12,014,834	$ 11,196,370
Past due 30 to 89 days	38,182	37,938	52,744
Past due 90 days or more	122,850	124,274	144,971
Nonaccrual	132,633	134,410	183,359
Total	12,093,564	12,311,456	11,577,444
Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	7,390,259	7,611,023	6,863,586
Past due 30 to 89 days	7,604	5,994	13,889
Past due 90 days or more	581	428	4,360
Nonaccrual	19,861	24,467	61,750
Total	7,418,305	7,641,912	6,943,585
Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,346,530	2,454,928	2,151,887
Past due 30 to 89 days	525	3,071	78
Past due 90 days or more	0	200	0
Nonaccrual	2,377	2,460	336
Total	2,349,432	2,460,659	2,152,301
Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,103,111	2,150,386	1,924,702
Past due 30 to 89 days	1,697	1,710	11,646
Past due 90 days or more	517	0	1,783
Nonaccrual	9,474	12,090	12,890
Total	2,114,799	2,164,186	1,951,021
Commercial [Member] | Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,082,491	1,103,307	979,188
Past due 30 to 89 days	270	5	897
Past due 90 days or more	0	50	1,701
Nonaccrual	2,239	3,077	15,388
Total	1,085,000	1,106,439	997,174
Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	397,746	346,442	317,577
Past due 30 to 89 days	224	35	0
Past due 90 days or more	0	0	727
Nonaccrual	1,848	2,007	23,402
Total	399,818	348,484	341,706
Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,073,804	1,077,022	974,336
Past due 30 to 89 days	4,806	1,040	730
Past due 90 days or more	64	178	149
Nonaccrual	2,962	3,166	7,946
Total	1,081,636	1,081,406	983,161
Commercial [Member] | Integrated food services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	173,800	190,416	204,101
Past due 30 to 89 days	0	6	0
Past due 90 days or more	0	0	0
Nonaccrual	0	684	0
Total	173,800	191,106	204,101
Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	212,777	288,522	311,795
Past due 30 to 89 days	82	127	538
Past due 90 days or more	0	0	0
Nonaccrual	961	983	1,788
Total	213,820	289,632	314,121
Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,214,348	2,159,287	2,157,056
Past due 30 to 89 days	2,303	5,657	7,084
Past due 90 days or more	3,334	3,429	1,684
Nonaccrual	65,175	60,626	86,475
Total	2,285,160	2,228,999	2,252,299
Commercial Real Estate [Member] | Construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	214,367	226,962	259,840
Past due 30 to 89 days	0	0	3,285
Past due 90 days or more	0	0	0
Nonaccrual	23,462	26,131	52,416
Total	237,829	253,093	315,541
Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	575,239	514,252	469,910
Past due 30 to 89 days	119	349	340
Past due 90 days or more	0	68	1,532
Nonaccrual	8,921	8,117	6,193
Total	584,279	522,786	477,975
Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	404,401	417,866	368,265
Past due 30 to 89 days	436	3,177	1,178
Past due 90 days or more	2,956	0	0
Nonaccrual	12,851	6,829	10,733
Total	420,644	427,872	380,176
Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	455,973	400,151	429,020
Past due 30 to 89 days	0	39	500
Past due 90 days or more	0	0	36
Nonaccrual	4,501	2,706	3,414
Total	460,474	402,896	432,970
Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	234,851	242,026	286,919
Past due 30 to 89 days	0	0	0
Past due 90 days or more	0	0	0
Nonaccrual	2,198	3,968	0
Total	237,049	245,994	286,919
Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	329,517	358,030	343,102
Past due 30 to 89 days	1,748	2,092	1,781
Past due 90 days or more	378	3,361	116
Nonaccrual	13,242	12,875	13,719
Total	344,885	376,358	358,718
Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,822,322	1,854,347	1,774,506
Past due 30 to 89 days	26,081	23,687	28,073
Past due 90 days or more	118,621	120,398	138,885
Nonaccrual	45,426	46,608	27,462
Total	2,012,450	2,045,040	1,968,926
Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,047,648	1,075,687	1,102,858
Past due 30 to 89 days	5,774	8,366	12,705
Past due 90 days or more	0	49	54
Nonaccrual	38,153	39,863	22,822
Total	1,091,575	1,123,965	1,138,439
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	25,915	26,560	28,750
Past due 30 to 89 days	17,669	13,046	13,281
Past due 90 days or more	118,621	120,349	138,831
Nonaccrual	214	489	0
Total	162,419	160,444	180,862
Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	748,759	752,100	642,898
Past due 30 to 89 days	2,638	2,275	2,087
Past due 90 days or more	0	0	0
Nonaccrual	7,059	6,256	4,640
Total	758,456	760,631	649,625
Consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	372,970	390,177	401,222
Past due 30 to 89 days	2,194	2,600	3,698
Past due 90 days or more	314	19	42
Nonaccrual	2,171	2,709	7,672
Total	377,649	395,505	412,634
Consumer [Member] | Indirect automobile [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	22,364	31,869	76,685
Past due 30 to 89 days	685	1,273	2,231
Past due 90 days or more	0	15	0
Nonaccrual	1,319	1,578	2,608
Total	24,368	34,735	81,524
Consumer [Member] | Other consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	350,606	358,308	324,537
Past due 30 to 89 days	1,509	1,327	1,467
Past due 90 days or more	314	4	42
Nonaccrual	852	1,131	5,064
Total	$ 353,281	$ 360,770	$ 331,110