Loans and Allowances for Credit Losses, Credit Quality Indicators (Details) (USD $)	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	$ 11,785,453,000		$ 10,789,740,000	$ 10,407,469,000
Non-Graded, Recorded Investment	1,898,286,000		2,002,524,000	1,942,631,000
Total	13,683,739,000		12,792,264,000	12,350,100,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	135,665,000		127,961,000	112,193,000
Non-Graded, Allowance	27,635,000		29,222,000	41,250,000
Allowance For Financing Receivable Total	191,244,000	190,690,000	185,396,000	194,325,000	203,124,000	215,507,000
Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	11,626,985,000		10,650,784,000	10,254,835,000
Non-Graded, Recorded Investment	1,852,621,000		1,966,324,000	1,907,425,000
Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	107,582,000		74,007,000	74,936,000
Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	50,886,000		64,949,000	77,698,000
Non-Graded, Recorded Investment	45,665,000		36,200,000	35,206,000
Commercial [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	8,545,949,000		7,888,219,000	7,553,151,000
Non-Graded, Recorded Investment	26,089,000		55,002,000	17,924,000
Total	8,572,038,000		7,943,221,000	7,571,075,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	85,892,000		78,250,000	60,570,000
Non-Graded, Allowance	883,000		930,000	1,210,000
Allowance For Financing Receivable Total	86,775,000		79,180,000	61,780,000
Commercial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	8,456,553,000		7,841,108,000	7,507,021,000
Non-Graded, Recorded Investment	26,035,000		54,929,000	17,877,000
Commercial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	73,046,000		30,424,000	26,655,000
Commercial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	16,350,000		16,687,000	19,475,000
Non-Graded, Recorded Investment	54,000		73,000	47,000
Energy [Member]
Recorded Investment [Abstract]
Total	2,551,699,000		2,351,760,000	2,311,991,000
Energy [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,519,924,000		2,347,519,000	2,305,225,000
Non-Graded, Recorded Investment	0		0	0
Energy [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	30,267,000		2,381,000	4,813,000
Energy [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,508,000		1,860,000	1,953,000
Non-Graded, Recorded Investment	0		0	0
Services [Member]
Recorded Investment [Abstract]
Total	2,487,817,000		2,282,210,000	2,148,551,000
Services [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,466,857,000		2,265,984,000	2,130,169,000
Non-Graded, Recorded Investment	0		0	0
Services [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	17,376,000		11,304,000	11,455,000
Services [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,584,000		4,922,000	6,927,000
Non-Graded, Recorded Investment	0		0	0
Wholesale/retail [Member]
Recorded Investment [Abstract]
Total	1,273,241,000		1,201,364,000	1,181,806,000
Wholesale/retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,264,333,000		1,191,791,000	1,171,923,000
Non-Graded, Recorded Investment	0		0	0
Wholesale/retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,406,000		2,604,000	2,660,000
Wholesale/retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	5,502,000		6,969,000	7,223,000
Non-Graded, Recorded Investment	0		0	0
Manufacturing [Member]
Recorded Investment [Abstract]
Total	479,543,000		391,751,000	382,460,000
Manufacturing [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	469,881,000		381,794,000	378,723,000
Non-Graded, Recorded Investment	0		0	0
Manufacturing [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	6,180,000		9,365,000	2,894,000
Manufacturing [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,482,000		592,000	843,000
Non-Graded, Recorded Investment	0		0	0
Healthcare [Member]
Recorded Investment [Abstract]
Total	1,382,399,000		1,274,246,000	1,160,212,000
Healthcare [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,376,399,000		1,272,626,000	1,158,436,000
Non-Graded, Recorded Investment	0		0	0
Healthcare [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,583,000		34,000	43,000
Healthcare [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,417,000		1,586,000	1,733,000
Non-Graded, Recorded Investment	0		0	0
Other commercial and industrial [Member]
Recorded Investment [Abstract]
Total	397,339,000		441,890,000	386,055,000
Other commercial and industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	359,159,000		381,394,000	362,545,000
Non-Graded, Recorded Investment	26,035,000		54,929,000	17,877,000
Other commercial and industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	11,234,000		4,736,000	4,790,000
Other commercial and industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	857,000		758,000	796,000
Non-Graded, Recorded Investment	54,000		73,000	47,000
Commercial Real Estate [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,724,199,000		2,415,353,000	2,349,229,000
Non-Graded, Recorded Investment	0		0	0
Total	2,724,199,000		2,415,353,000	2,349,229,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	42,433,000		41,573,000	45,062,000
Non-Graded, Allowance	0		0	0
Allowance For Financing Receivable Total	42,433,000		41,573,000	45,062,000
Commercial Real Estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	2,660,335,000		2,334,998,000	2,253,925,000
Non-Graded, Recorded Investment	0		0	0
Commercial Real Estate [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	33,204,000		39,505,000	42,802,000
Commercial Real Estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	30,660,000		40,850,000	52,502,000
Non-Graded, Recorded Investment	0		0	0
Residential construction and land development [Member]
Recorded Investment [Abstract]
Total	175,228,000		206,258,000	216,456,000
Residential construction and land development [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	145,223,000		173,488,000	178,278,000
Non-Graded, Recorded Investment	0		0	0
Residential construction and land development [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	15,371,000		15,393,000	17,394,000
Residential construction and land development [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	14,634,000		17,377,000	20,784,000
Non-Graded, Recorded Investment	0		0	0
Retail [Member]
Recorded Investment [Abstract]
Total	611,265,000		586,047,000	556,918,000
Retail [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	605,718,000		579,506,000	548,197,000
Non-Graded, Recorded Investment	0		0	0
Retail [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,538,000		1,684,000	807,000
Retail [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	4,009,000		4,857,000	7,914,000
Non-Graded, Recorded Investment	0		0	0
Office [Member]
Recorded Investment [Abstract]
Total	438,909,000		411,499,000	422,043,000
Office [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	434,829,000		403,951,000	413,083,000
Non-Graded, Recorded Investment	0		0	0
Office [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	581,000		1,157,000	2,122,000
Office [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,499,000		6,391,000	6,838,000
Non-Graded, Recorded Investment	0		0	0
Multifamily [Member]
Recorded Investment [Abstract]
Total	739,757,000		576,502,000	520,454,000
Multifamily [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	725,720,000		562,800,000	504,548,000
Non-Graded, Recorded Investment	0		0	0
Multifamily [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	14,037,000		13,695,000	11,556,000
Multifamily [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		7,000	4,350,000
Non-Graded, Recorded Investment	0		0	0
Industrial [Member]
Recorded Investment [Abstract]
Total	371,426,000		243,877,000	245,022,000
Industrial [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	371,426,000		243,625,000	244,768,000
Non-Graded, Recorded Investment	0		0	0
Industrial [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	254,000
Industrial [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		252,000	0
Non-Graded, Recorded Investment	0		0	0
Other commercial real estate [Member]
Recorded Investment [Abstract]
Total	387,614,000		391,170,000	388,336,000
Other commercial real estate [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	377,419,000		371,628,000	365,051,000
Non-Graded, Recorded Investment	0		0	0
Other commercial real estate [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,677,000		7,576,000	10,669,000
Other commercial real estate [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	8,518,000		11,966,000	12,616,000
Non-Graded, Recorded Investment	0		0	0
Residential Mortgage [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	200,701,000		220,635,000	236,399,000
Non-Graded, Recorded Investment	1,778,962,000		1,831,391,000	1,798,366,000
Total	1,979,663,000		2,052,026,000	2,034,765,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	4,083,000		5,481,000	3,764,000
Non-Graded, Allowance	23,133,000		23,984,000	34,533,000
Allowance For Financing Receivable Total	27,216,000		29,465,000	38,297,000
Residential Mortgage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	195,688,000		210,142,000	226,325,000
Non-Graded, Recorded Investment	1,733,756,000		1,796,281,000	1,764,551,000
Residential Mortgage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,312,000		3,283,000	4,633,000
Residential Mortgage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,701,000		7,210,000	5,441,000
Non-Graded, Recorded Investment	45,206,000		35,110,000	33,815,000
Permanent mortage [Member]
Recorded Investment [Abstract]
Total	991,107,000		1,062,744,000	1,078,661,000
Permanent mortage [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	195,688,000		210,142,000	222,630,000
Non-Graded, Recorded Investment	758,970,000		815,040,000	819,601,000
Permanent mortage [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	1,312,000		3,283,000	4,633,000
Permanent mortage [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	3,701,000		7,210,000	5,441,000
Non-Graded, Recorded Investment	31,436,000		27,069,000	26,356,000
Permanent mortgages guaranteed by US govenment agencies [Member]
Recorded Investment [Abstract]
Total	198,488,000		181,598,000	163,919,000
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	194,653,000		180,821,000	163,342,000
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	3,835,000		777,000	577,000
Home equity {Member]
Recorded Investment [Abstract]
Total	790,068,000		807,684,000	792,185,000
Home equity {Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	0		0	3,695,000
Non-Graded, Recorded Investment	780,133,000		800,420,000	781,608,000
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	9,935,000		7,264,000	6,882,000
Consumer [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	314,604,000		265,533,000	268,690,000
Non-Graded, Recorded Investment	93,235,000		116,131,000	126,341,000
Total	407,839,000		381,664,000	395,031,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	3,257,000		2,657,000	2,797,000
Non-Graded, Allowance	3,619,000		4,308,000	5,507,000
Allowance For Financing Receivable Total	6,876,000		6,965,000	8,304,000
Consumer [Member] | Performing [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	314,409,000		264,536,000	267,564,000
Non-Graded, Recorded Investment	92,830,000		115,114,000	124,997,000
Consumer [Member] | Potential Problem [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	20,000		795,000	846,000
Consumer [Member] | Nonaccrual [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	175,000		202,000	280,000
Non-Graded, Recorded Investment	405,000		1,017,000	1,344,000
Specific Allowance [Member]
Recorded Investment [Abstract]
Internally Risk Graded, Recorded Investment	11,785,453,000		10,789,740,000	10,407,469,000
Non-Graded, Recorded Investment	1,898,286,000		2,002,524,000	1,942,631,000
Total	13,683,739,000		12,792,264,000	12,350,100,000
Related Allowance [Abstract]
Internally Risk Graded, Allowance	135,665,000		127,961,000	112,193,000
Non-Graded, Allowance	27,635,000		29,222,000	41,250,000
Allowance For Financing Receivable Total	163,300,000		157,183,000	153,443,000
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	$ 27,944,000	$ 26,949,000	$ 28,213,000	$ 40,882,000	$ 42,449,000	$ 44,187,000