Loans and Allowances for Credit Losses Part 7 (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing receivable, recorded investment, aging [Abstract]
Current	$ 11,503,763	$ 10,846,838	$ 10,683,170
Past due 30 to 89 days	70,178	63,822	70,631
Past due 90 days or more	126,527	157,797	141,293
Nonaccrual	131,899	201,286	229,475
Total	11,832,367	11,269,743	11,124,569
Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	7,237,676	6,465,447	6,315,495
Past due 30 to 89 days	12,916	19,125	21,182
Past due 90 days or more	863	1,687	1,189
Nonaccrual	21,762	68,811	83,736
Total	7,273,217	6,555,070	6,421,602
Commercial [Member] | Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,425,408	2,003,192	1,744,256
Past due 30 to 89 days	5,002	1,065	599
Past due 90 days or more	0	448	448
Nonaccrual	3,063	336	3,900
Total	2,433,473	2,005,041	1,749,203
Commercial [Member] | Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,880,350	1,729,775	1,847,318
Past due 30 to 89 days	741	13,608	6,980
Past due 90 days or more	538	1,187	468
Nonaccrual	10,099	16,968	18,181
Total	1,891,728	1,761,538	1,872,947
Commercial [Member] | Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,075,936	945,776	980,829
Past due 30 to 89 days	1,324	470	12,880
Past due 90 days or more	0	0	273
Nonaccrual	2,007	21,180	27,088
Total	1,079,267	967,426	1,021,070
Commercial [Member] | Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	359,975	313,028	345,355
Past due 30 to 89 days	834	654	28
Past due 90 days or more	0	0	0
Nonaccrual	2,283	23,051	27,691
Total	363,092	336,733	373,074
Commercial [Member] | Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,029,208	971,265	908,542
Past due 30 to 89 days	4,775	1,362	89
Past due 90 days or more	0	47	0
Nonaccrual	3,305	5,486	5,715
Total	1,037,288	978,160	914,346
Commercial [Member] | Integrated food services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	213,832	204,306	192,179
Past due 30 to 89 days	0	0	21
Past due 90 days or more	0	5	0
Nonaccrual	0	0	0
Total	213,832	204,311	192,200
Commercial [Member] | Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	252,967	298,105	297,016
Past due 30 to 89 days	240	1,966	585
Past due 90 days or more	325	0	0
Nonaccrual	1,005	1,790	1,161
Total	254,537	301,861	298,762
Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,073,617	2,186,601	2,151,696
Past due 30 to 89 days	16,112	5,372	11,089
Past due 90 days or more	36	137	0
Nonaccrual	75,761	99,193	110,048
Total	2,165,526	2,291,303	2,272,833
Commercial Real Estate [Member] | Construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	241,069	278,901	297,573
Past due 30 to 89 days	10,297	1,279	685
Past due 90 days or more	35	0	0
Nonaccrual	38,143	61,874	72,207
Total	289,544	342,054	370,465
Commercial Real Estate [Member] | Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	517,991	502,167	447,820
Past due 30 to 89 days	368	372	2,864
Past due 90 days or more	0	0	0
Nonaccrual	6,692	6,863	6,492
Total	525,051	509,402	457,176
Commercial Real Estate [Member] | Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	394,984	394,227	409,965
Past due 30 to 89 days	1,190	239	352
Past due 90 days or more	0	0	0
Nonaccrual	9,833	11,457	11,967
Total	406,007	405,923	422,284
Commercial Real Estate [Member] | Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	395,333	365,477	384,268
Past due 30 to 89 days	35	38	0
Past due 90 days or more	0	0	0
Nonaccrual	3,145	3,513	4,036
Total	398,513	369,028	388,304
Commercial Real Estate [Member] | Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	181,271	278,186	224,222
Past due 30 to 89 days	1,831	0	0
Past due 90 days or more	0	0	0
Nonaccrual	4,064	0	0
Total	187,166	278,186	224,222
Commercial Real Estate [Member] | Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	342,969	367,643	387,848
Past due 30 to 89 days	2,391	3,444	7,188
Past due 90 days or more	1	137	0
Nonaccrual	13,884	15,486	15,346
Total	359,245	386,710	410,382
Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,826,574	1,756,358	1,745,457
Past due 30 to 89 days	37,543	32,458	32,691
Past due 90 days or more	125,596	155,944	140,022
Nonaccrual	29,267	29,767	31,731
Total	2,018,980	1,974,527	1,949,901
Residential Mortgage [Member] | Permanent mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,093,109	1,110,418	1,130,567
Past due 30 to 89 days	17,953	17,259	22,127
Past due 90 days or more	250	601	130
Nonaccrual	23,207	25,366	27,486
Total	1,134,519	1,153,644	1,180,310
Residential Mortgage [Member] | Permanent mortgages guaranteed by U.S. government agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	26,908	20,998	25,234
Past due 30 to 89 days	16,629	12,163	8,414
Past due 90 days or more	125,346	155,301	139,892
Nonaccrual	510	0	0
Total	169,393	188,462	173,540
Residential Mortgage [Member] | Home equity [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	706,557	624,942	589,656
Past due 30 to 89 days	2,961	3,036	2,150
Past due 90 days or more	0	42	0
Nonaccrual	5,550	4,401	4,245
Total	715,068	632,421	596,051
Consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	365,896	438,432	470,522
Past due 30 to 89 days	3,607	6,867	5,669
Past due 90 days or more	32	29	82
Nonaccrual	5,109	3,515	3,960
Total	374,644	448,843	480,233
Consumer [Member] | Indirect automobile [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	43,588	98,345	123,160
Past due 30 to 89 days	1,729	4,581	4,718
Past due 90 days or more	32	29	0
Nonaccrual	1,932	2,194	2,418
Total	47,281	105,149	130,296
Consumer [Member] | Other consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	322,308	340,087	347,362
Past due 30 to 89 days	1,878	2,286	951
Past due 90 days or more	0	0	82
Nonaccrual	3,177	1,321	1,542
Total	$ 327,363	$ 343,694	$ 349,937