Loans and Allowances for Credit Losses Part 7 (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing receivable, recorded investment, aging [Abstract]
Current	$ 12,014,834	$ 10,850,897
Past due 30 to 89 days	37,938	63,527
Past due 90 days or more	124,274	154,033
Nonaccrual	134,410	201,286
Total	12,311,456	11,269,743
Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	7,611,023	6,465,447
Past due 30 to 89 days	5,994	19,125
Past due 90 days or more	428	1,687
Nonaccrual	24,467	68,811
Total	7,641,912	6,555,070
Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,454,928	2,003,192
Past due 30 to 89 days	3,071	1,065
Past due 90 days or more	200	448
Nonaccrual	2,460	336
Total	2,460,659	2,005,041
Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,150,386	1,729,775
Past due 30 to 89 days	1,710	13,608
Past due 90 days or more	0	1,187
Nonaccrual	12,090	16,968
Total	2,164,186	1,761,538
Commercial [Member] | Wholesale and retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,103,307	945,776
Past due 30 to 89 days	5	470
Past due 90 days or more	50	0
Nonaccrual	3,077	21,180
Total	1,106,439	967,426
Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	346,442	313,028
Past due 30 to 89 days	35	654
Past due 90 days or more	0	0
Nonaccrual	2,007	23,051
Total	348,484	336,733
Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,077,022	971,265
Past due 30 to 89 days	1,040	1,362
Past due 90 days or more	178	47
Nonaccrual	3,166	5,486
Total	1,081,406	978,160
Commercial [Member] | Integrated food services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	190,416	204,306
Past due 30 to 89 days	6	0
Past due 90 days or more	0	5
Nonaccrual	684	0
Total	191,106	204,311
Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	288,522	298,105
Past due 30 to 89 days	127	1,966
Past due 90 days or more	0	0
Nonaccrual	983	1,790
Total	289,632	301,861
Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,159,287	2,186,601
Past due 30 to 89 days	5,657	5,372
Past due 90 days or more	3,429	137
Nonaccrual	60,626	99,193
Total	2,228,999	2,291,303
Commercial Real Estate [Member] | Construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	226,962	278,901
Past due 30 to 89 days	0	1,279
Past due 90 days or more	0	0
Nonaccrual	26,131	61,874
Total	253,093	342,054
Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	514,252	502,167
Past due 30 to 89 days	349	372
Past due 90 days or more	68	0
Nonaccrual	8,117	6,863
Total	522,786	509,402
Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	417,866	394,227
Past due 30 to 89 days	3,177	239
Past due 90 days or more	0	0
Nonaccrual	6,829	11,457
Total	427,872	405,923
Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	400,151	365,477
Past due 30 to 89 days	39	38
Past due 90 days or more	0	0
Nonaccrual	2,706	3,513
Total	402,896	369,028
Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	242,026	278,186
Past due 30 to 89 days	0	0
Past due 90 days or more	0	0
Nonaccrual	3,968	0
Total	245,994	278,186
Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	358,030	367,643
Past due 30 to 89 days	2,092	3,444
Past due 90 days or more	3,361	137
Nonaccrual	12,875	15,486
Total	376,358	386,710
Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,854,347	1,760,417
Past due 30 to 89 days	23,687	32,163
Past due 90 days or more	120,398	152,180
Nonaccrual	46,608	29,767
Total	2,045,040	1,974,527
Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,075,687	1,113,907
Past due 30 to 89 days	8,366	17,259
Past due 90 days or more	49	601
Nonaccrual	39,863	25,366
Total	1,123,965	1,157,133
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	26,560	21,568
Past due 30 to 89 days	13,046	11,868
Past due 90 days or more	120,349	151,537
Nonaccrual	489	0
Total	160,444	184,973
Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	752,100	624,942
Past due 30 to 89 days	2,275	3,036
Past due 90 days or more	0	42
Nonaccrual	6,256	4,401
Total	760,631	632,421
Consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	390,177	438,432
Past due 30 to 89 days	2,600	6,867
Past due 90 days or more	19	29
Nonaccrual	2,709	3,515
Total	395,505	448,843
Consumer [Member] | Indirect automobile [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	31,869	98,345
Past due 30 to 89 days	1,273	4,581
Past due 90 days or more	15	29
Nonaccrual	1,578	2,194
Total	34,735	105,149
Consumer [Member] | Other consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	358,308	340,087
Past due 30 to 89 days	1,327	2,286
Past due 90 days or more	4	0
Nonaccrual	1,131	1,321
Total	$ 360,770	$ 343,694