Loans and Allowances for Credit Losses Part 3 (Details) (USD $)	Sep. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	$ 10,407,469,000		$ 10,350,320,000	$ 9,905,051,000
Non-Graded, Recorded Investment	1,942,631,000		1,961,136,000	1,927,316,000
Total	12,350,100,000		12,311,456,000	11,832,367,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	112,193,000		127,322,000	150,507,000
Non-Graded, Allowance	41,250,000		43,998,000	42,335,000
Allowance For Financing Receivable Total	194,325,000	203,124,000	215,507,000	233,756,000	231,669,000	253,481,000
Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,254,835,000		10,111,255,000	9,644,865,000
Non-Graded, Recorded Investment	1,907,425,000		1,924,879,000	1,905,500,000
Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	74,936,000		140,912,000	150,103,000
Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	77,698,000		98,153,000	110,083,000
Non-Graded, Recorded Investment	35,206,000		36,257,000	21,816,000
Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,553,151,000		7,624,442,000	7,249,429,000
Non-Graded, Recorded Investment	17,924,000		17,470,000	17,478,000
Total	7,571,075,000		7,641,912,000	7,266,907,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	60,570,000		64,181,000	80,676,000
Non-Graded, Allowance	1,210,000		1,099,000	1,103,000
Allowance For Financing Receivable Total	61,780,000		65,280,000	81,779,000
Commercial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,507,021,000		7,533,757,000	7,161,823,000
Non-Graded, Recorded Investment	17,877,000		17,406,000	17,405,000
Commercial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	26,655,000		66,282,000	65,917,000
Commercial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	19,475,000		24,403,000	21,689,000
Non-Graded, Recorded Investment	47,000		64,000	73,000
Energy [Member]
Recorded Investment [Abstract]
Total	2,311,991,000		2,460,659,000	2,416,877,000
Energy [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,305,225,000		2,448,954,000	2,403,364,000
Non-Graded, Recorded Investment	0		0	0
Energy [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,813,000		9,245,000	10,450,000
Energy [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,953,000		2,460,000	3,063,000
Non-Graded, Recorded Investment	0		0	0
Services [Member]
Recorded Investment [Abstract]
Total	2,148,551,000		2,164,186,000	1,967,568,000
Services [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,130,169,000		2,119,734,000	1,923,017,000
Non-Graded, Recorded Investment	0		0	0
Services [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	11,455,000		32,362,000	34,452,000
Services [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,927,000		12,090,000	10,099,000
Non-Graded, Recorded Investment	0		0	0
Wholesale/retail [Member]
Recorded Investment [Abstract]
Total	1,181,806,000		1,106,439,000	1,060,061,000
Wholesale/retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,171,923,000		1,093,413,000	1,053,813,000
Non-Graded, Recorded Investment	0		0	0
Wholesale/retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,660,000		9,949,000	4,241,000
Wholesale/retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,223,000		3,077,000	2,007,000
Non-Graded, Recorded Investment	0		0	0
Manufacturing [Member]
Recorded Investment [Abstract]
Total	382,460,000		348,484,000	343,360,000
Manufacturing [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	378,723,000		337,132,000	330,608,000
Non-Graded, Recorded Investment	0		0	0
Manufacturing [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,894,000		9,345,000	10,469,000
Manufacturing [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	843,000		2,007,000	2,283,000
Non-Graded, Recorded Investment	0		0	0
Healthcare [Member]
Recorded Investment [Abstract]
Total	1,160,212,000		1,081,406,000	1,022,851,000
Healthcare [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,158,436,000		1,077,773,000	1,019,362,000
Non-Graded, Recorded Investment	0		0	0
Healthcare [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	43,000		467,000	184,000
Healthcare [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,733,000		3,166,000	3,305,000
Non-Graded, Recorded Investment	0		0	0
Integrated food services [Member]
Recorded Investment [Abstract]
Total	141,440,000		191,106,000	200,453,000
Integrated food services [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	136,650,000		190,422,000	199,769,000
Non-Graded, Recorded Investment	0		0	0
Integrated food services [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,790,000		0	684,000
Integrated food services [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		684,000	0
Non-Graded, Recorded Investment	0		0	0
Other commercial and industrial [Member]
Recorded Investment [Abstract]
Total	244,615,000		289,632,000	255,737,000
Other commercial and industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	225,895,000		266,329,000	231,890,000
Non-Graded, Recorded Investment	17,877,000		17,406,000	17,405,000
Other commercial and industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		4,914,000	5,437,000
Other commercial and industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	796,000		919,000	932,000
Non-Graded, Recorded Investment	47,000		64,000	73,000
Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,349,229,000		2,228,999,000	2,177,235,000
Non-Graded, Recorded Investment	0		0	37,000
Total	2,349,229,000		2,228,999,000	2,177,272,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	45,062,000		54,884,000	60,704,000
Non-Graded, Allowance	0		0	0
Allowance For Financing Receivable Total	45,062,000		54,884,000	60,704,000
Commercial Real Estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,253,925,000		2,105,105,000	2,030,764,000
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	42,802,000		63,268,000	70,747,000
Commercial Real Estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	52,502,000		60,626,000	75,724,000
Non-Graded, Recorded Investment	0		0	37,000
Construction and land development [Member]
Recorded Investment [Abstract]
Total	216,456,000		253,093,000	293,733,000
Construction and land development [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	178,278,000		204,010,000	230,022,000
Non-Graded, Recorded Investment	0		0	0
Construction and land development [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	17,394,000		22,952,000	25,568,000
Construction and land development [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	20,784,000		26,131,000	38,143,000
Non-Graded, Recorded Investment	0		0	0
Retail [Member]
Recorded Investment [Abstract]
Total	556,918,000		522,786,000	535,456,000
Retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	548,197,000		508,342,000	520,568,000
Non-Graded, Recorded Investment	0		0	0
Retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	807,000		6,327,000	8,196,000
Retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	7,914,000		8,117,000	6,692,000
Non-Graded, Recorded Investment	0		0	0
Office [Member]
Recorded Investment [Abstract]
Total	422,043,000		427,872,000	414,246,000
Office [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	413,083,000		405,763,000	391,859,000
Non-Graded, Recorded Investment	0		0	0
Office [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,122,000		15,280,000	12,554,000
Office [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,838,000		6,829,000	9,833,000
Non-Graded, Recorded Investment	0		0	0
Multifamily [Member]
Recorded Investment [Abstract]
Total	520,454,000		402,896,000	393,129,000
Multifamily [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	504,548,000		393,566,000	383,317,000
Non-Graded, Recorded Investment	0		0	0
Multifamily [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	11,556,000		6,624,000	6,667,000
Multifamily [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,350,000		2,706,000	3,145,000
Non-Graded, Recorded Investment	0		0	0
Industrial [Member]
Recorded Investment [Abstract]
Total	245,022,000		245,994,000	183,846,000
Industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	244,768,000		241,761,000	175,339,000
Non-Graded, Recorded Investment	0		0	0
Industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	254,000		265,000	4,443,000
Industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		3,968,000	4,064,000
Non-Graded, Recorded Investment	0		0	0
Other commercial real estate [Member]
Recorded Investment [Abstract]
Total	388,336,000		376,358,000	356,862,000
Other commercial real estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	365,051,000		351,663,000	329,659,000
Non-Graded, Recorded Investment	0		0	0
Other commercial real estate [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,669,000		11,820,000	13,319,000
Other commercial real estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	12,616,000		12,875,000	13,847,000
Non-Graded, Recorded Investment	0		0	37,000
Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	236,399,000		265,503,000	275,490,000
Non-Graded, Recorded Investment	1,798,366,000		1,779,537,000	1,740,813,000
Total	2,034,765,000		2,045,040,000	2,016,303,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	3,764,000		5,270,000	6,416,000
Non-Graded, Allowance	34,533,000		36,433,000	34,600,000
Allowance For Financing Receivable Total	38,297,000		41,703,000	41,016,000
Residential Mortgage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	226,325,000		242,823,000	253,859,000
Non-Graded, Recorded Investment	1,764,551,000		1,745,338,000	1,721,401,000
Residential Mortgage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,633,000		10,271,000	11,776,000
Residential Mortgage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	5,441,000		12,409,000	9,855,000
Non-Graded, Recorded Investment	33,815,000		34,199,000	19,412,000
Permanent mortage [Member]
Recorded Investment [Abstract]
Total	1,078,661,000		1,123,965,000	1,138,960,000
Permanent mortage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	222,630,000		242,823,000	253,859,000
Non-Graded, Recorded Investment	819,601,000		831,008,000	850,118,000
Permanent mortage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,633,000		10,271,000	11,776,000
Permanent mortage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	5,441,000		12,409,000	9,855,000
Non-Graded, Recorded Investment	26,356,000		27,454,000	13,352,000
Permanent mortgages guaranteed by US govenment agencies [Member]
Recorded Investment [Abstract]
Total	163,919,000		160,444,000	162,271,000
Permanent mortgages guaranteed by US govenment agencies [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	163,342,000		159,955,000	161,761,000
Permanent mortgages guaranteed by US govenment agencies [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Permanent mortgages guaranteed by US govenment agencies [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	577,000		489,000	510,000
Home equity {Member]
Recorded Investment [Abstract]
Total	792,185,000		760,631,000	715,072,000
Home equity {Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,695,000		0	0
Non-Graded, Recorded Investment	781,608,000		754,375,000	709,522,000
Home equity {Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Home equity {Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	6,882,000		6,256,000	5,550,000
Consumer [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	268,690,000		231,376,000	202,897,000
Non-Graded, Recorded Investment	126,341,000		164,129,000	168,988,000
Total	395,031,000		395,505,000	371,885,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	2,797,000		2,987,000	2,711,000
Non-Graded, Allowance	5,507,000		6,466,000	6,632,000
Allowance For Financing Receivable Total	8,304,000		9,453,000	9,343,000
Consumer [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	267,564,000		229,570,000	198,419,000
Non-Graded, Recorded Investment	124,997,000		162,135,000	166,694,000
Consumer [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	846,000		1,091,000	1,663,000
Consumer [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	280,000		715,000	2,815,000
Non-Graded, Recorded Investment	1,344,000		1,994,000	2,294,000
Indirect automobile [Member]
Recorded Investment [Abstract]
Total	10,757,000		34,735,000	47,281,000
Indirect automobile [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	9,800,000		33,157,000	45,349,000
Indirect automobile [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Indirect automobile [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	957,000		1,578,000	1,932,000
Other consumer [Member]
Recorded Investment [Abstract]
Total	384,274,000		360,770,000	324,604,000
Other consumer [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	267,564,000		229,570,000	198,419,000
Non-Graded, Recorded Investment	115,197,000		128,978,000	121,345,000
Other consumer [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	846,000		1,091,000	1,663,000
Other consumer [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	280,000		715,000	2,815,000
Non-Graded, Recorded Investment	387,000		416,000	362,000
Specific Allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	10,407,469,000		10,350,320,000	9,905,051,000
Non-Graded, Recorded Investment	1,942,631,000		1,961,136,000	1,927,316,000
Total	12,350,100,000		12,311,456,000	11,832,367,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	112,193,000		127,322,000	150,507,000
Non-Graded, Allowance	41,250,000		43,998,000	42,335,000
Allowance For Financing Receivable Total	153,443,000		171,320,000	192,842,000
Nonspecific Allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	0
Non-Graded, Recorded Investment	0		0	0
Total	0		0	0
Related Allowance [Abstract]
Internally Risk Graded, Allowance	0		0	0
Non-Graded, Allowance	0		0	0
Allowance For Financing Receivable Total	$ 40,882,000	$ 42,449,000	$ 44,187,000	$ 40,914,000	$ 40,858,000	$ 46,350,000