Loans and Allowances for Credit Losses Part 7 (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Financing receivable, recorded investment, aging [Abstract]
Current	$ 12,079,201,000	$ 12,014,834,000	$ 11,503,763,000
Past due 30 to 89 days	34,089,000	37,938,000	70,178,000
Past due 90 days or more	123,906,000	124,274,000	126,527,000
Nonaccrual	112,904,000	134,410,000	131,899,000
Total	12,350,100,000	12,311,456,000	11,832,367,000
Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	7,547,586,000	7,611,023,000	7,231,366,000
Past due 30 to 89 days	3,882,000	5,994,000	12,916,000
Past due 90 days or more	85,000	428,000	863,000
Nonaccrual	19,522,000	24,467,000	21,762,000
Total	7,571,075,000	7,641,912,000	7,266,907,000
Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,308,639,000	2,454,928,000	2,408,812,000
Past due 30 to 89 days	1,399,000	3,071,000	5,002,000
Past due 90 days or more	0	200,000	0
Nonaccrual	1,953,000	2,460,000	3,063,000
Total	2,311,991,000	2,460,659,000	2,416,877,000
Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,140,835,000	2,150,386,000	1,956,190,000
Past due 30 to 89 days	704,000	1,710,000	741,000
Past due 90 days or more	85,000	0	538,000
Nonaccrual	6,927,000	12,090,000	10,099,000
Total	2,148,551,000	2,164,186,000	1,967,568,000
Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,173,628,000	1,103,307,000	1,056,730,000
Past due 30 to 89 days	955,000	5,000	1,324,000
Past due 90 days or more	0	50,000	0
Nonaccrual	7,223,000	3,077,000	2,007,000
Total	1,181,806,000	1,106,439,000	1,060,061,000
Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	381,048,000	346,442,000	340,243,000
Past due 30 to 89 days	569,000	35,000	834,000
Past due 90 days or more	0	0	0
Nonaccrual	843,000	2,007,000	2,283,000
Total	382,460,000	348,484,000	343,360,000
Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,158,340,000	1,077,022,000	1,014,771,000
Past due 30 to 89 days	139,000	1,040,000	4,775,000
Past due 90 days or more	0	178,000	0
Nonaccrual	1,733,000	3,166,000	3,305,000
Total	1,160,212,000	1,081,406,000	1,022,851,000
Integrated food services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	141,440,000	190,416,000	200,453,000
Past due 30 to 89 days	0	6,000	0
Past due 90 days or more	0	0	0
Nonaccrual	0	684,000	0
Total	141,440,000	191,106,000	200,453,000
Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	243,656,000	288,522,000	254,167,000
Past due 30 to 89 days	116,000	127,000	240,000
Past due 90 days or more	0	0	325,000
Nonaccrual	843,000	983,000	1,005,000
Total	244,615,000	289,632,000	255,737,000
Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,295,456,000	2,159,287,000	2,085,363,000
Past due 30 to 89 days	1,271,000	5,657,000	16,112,000
Past due 90 days or more	0	3,429,000	36,000
Nonaccrual	52,502,000	60,626,000	75,761,000
Total	2,349,229,000	2,228,999,000	2,177,272,000
Construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	195,672,000	226,962,000	245,258,000
Past due 30 to 89 days	0	0	10,297,000
Past due 90 days or more	0	0	35,000
Nonaccrual	20,784,000	26,131,000	38,143,000
Total	216,456,000	253,093,000	293,733,000
Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	548,810,000	514,252,000	528,396,000
Past due 30 to 89 days	194,000	349,000	368,000
Past due 90 days or more	0	68,000	0
Nonaccrual	7,914,000	8,117,000	6,692,000
Total	556,918,000	522,786,000	535,456,000
Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	415,205,000	417,866,000	403,223,000
Past due 30 to 89 days	0	3,177,000	1,190,000
Past due 90 days or more	0	0	0
Nonaccrual	6,838,000	6,829,000	9,833,000
Total	422,043,000	427,872,000	414,246,000
Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	516,104,000	400,151,000	389,949,000
Past due 30 to 89 days	0	39,000	35,000
Past due 90 days or more	0	0	0
Nonaccrual	4,350,000	2,706,000	3,145,000
Total	520,454,000	402,896,000	393,129,000
Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	244,415,000	242,026,000	177,951,000
Past due 30 to 89 days	607,000	0	1,831,000
Past due 90 days or more	0	0	0
Nonaccrual	0	3,968,000	4,064,000
Total	245,022,000	245,994,000	183,846,000
Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	375,250,000	358,030,000	340,586,000
Past due 30 to 89 days	470,000	2,092,000	2,391,000
Past due 90 days or more	0	3,361,000	1,000
Nonaccrual	12,616,000	12,875,000	13,884,000
Total	388,336,000	376,358,000	356,862,000
Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,844,555,000	1,854,347,000	1,823,897,000
Past due 30 to 89 days	27,208,000	23,687,000	37,543,000
Past due 90 days or more	123,746,000	120,398,000	125,596,000
Nonaccrual	39,256,000	46,608,000	29,267,000
Total	2,034,765,000	2,045,040,000	2,016,303,000
Permanent mortage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,040,616,000	1,075,687,000	1,097,550,000
Past due 30 to 89 days	6,248,000	8,366,000	17,953,000
Past due 90 days or more	0	49,000	250,000
Nonaccrual	31,797,000	39,863,000	23,207,000
Total	1,078,661,000	1,123,965,000	1,138,960,000
Permanent mortgages guaranteed by US govenment agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	20,985,000	26,560,000	19,786,000
Past due 30 to 89 days	18,639,000	13,046,000	16,629,000
Past due 90 days or more	123,718,000	120,349,000	125,346,000
Nonaccrual	577,000	489,000	510,000
Total	163,919,000	160,444,000	162,271,000
Home equity {Member]
Financing receivable, recorded investment, aging [Abstract]
Current	782,954,000	752,100,000	706,561,000
Past due 30 to 89 days	2,321,000	2,275,000	2,961,000
Past due 90 days or more	28,000	0	0
Nonaccrual	6,882,000	6,256,000	5,550,000
Total	792,185,000	760,631,000	715,072,000
Consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	391,604,000	390,177,000	363,137,000
Past due 30 to 89 days	1,728,000	2,600,000	3,607,000
Past due 90 days or more	75,000	19,000	32,000
Nonaccrual	1,624,000	2,709,000	5,109,000
Total	395,031,000	395,505,000	371,885,000
Indirect automobile [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	9,416,000	31,869,000	43,588,000
Past due 30 to 89 days	384,000	1,273,000	1,729,000
Past due 90 days or more	0	15,000	32,000
Nonaccrual	957,000	1,578,000	1,932,000
Total	10,757,000	34,735,000	47,281,000
Other consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	382,188,000	358,308,000	319,549,000
Past due 30 to 89 days	1,344,000	1,327,000	1,878,000
Past due 90 days or more	75,000	4,000	0
Nonaccrual	667,000	1,131,000	3,177,000
Total	$ 384,274,000	$ 360,770,000	$ 324,604,000