Derivatives, Fair Value of Derivatives Contracts (Details) (USD $)	Sep. 30, 2011		Dec. 31, 2010		Sep. 30, 2010
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	$ 15,801,043,000	[1]	$ 14,091,727,000	[1]	$ 15,514,222,000	[1]
Derivative Liability, Notional Amount, Gross Basis	15,848,918,000	[1]	14,038,235,000	[1]	15,095,739,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	572,373,000		498,443,000		515,012,000
Derivative Asset, Fair Value, Net Asset	370,616,000		270,445,000		266,104,000
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	562,105,000		497,388,000		503,454,000
Derivative Liability, Fair Value, Net Liability	341,822,000		215,420,000		218,296,000
Increase in cash margin obligation for derivative holdings with a decrease in credit rating from A1 to below investment grade	41,000,000
Interest Rate Contract [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	13,576,276,000	[1],[2]	11,664,409,000	[1]	12,922,733,000	[1]
Derivative Liability, Notional Amount, Gross Basis	13,441,006,000	[1],[2]	11,524,077,000	[1]	12,358,978,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	281,479,000	[2]	235,961,000		162,377,000
Derivative Asset, Fair Value, Net Asset	219,951,000	[2],[3]	141,279,000	[3]	116,257,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	278,936,000	[2]	233,421,000		159,901,000
Derivative Liability, Fair Value, Net Liability	217,408,000	[2],[3]	138,739,000	[3]	113,781,000	[3]
Energy Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	1,726,402,000	[1]	1,914,519,000	[1]	2,120,942,000	[1]
Derivative Liability, Notional Amount, Gross Basis	1,965,233,000	[1]	2,103,923,000	[1]	2,377,861,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	200,142,000		188,655,000		280,623,000
Derivative Asset, Fair Value, Net Asset	102,938,000	[3]	76,746,000	[3]	101,636,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	198,725,000		191,075,000		280,138,000
Derivative Liability, Fair Value, Net Liability	101,521,000	[3]	79,166,000	[3]	101,151,000	[3]
Agriculture Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	190,100,000	[1]	183,250,000	[1]	153,551,000	[1]
Derivative Liability, Notional Amount, Gross Basis	190,700,000	[1]	186,709,000	[1]	162,927,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	8,100,000		10,616,000		5,609,000
Derivative Asset, Fair Value, Net Asset	2,373,000	[3]	4,226,000	[3]	1,715,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	8,012,000		10,534,000		5,500,000
Derivative Liability, Fair Value, Net Liability	2,285,000	[3]	4,144,000	[3]	1,606,000	[3]
Foreign Exchange Contract [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	65,747,000	[1]	45,014,000	[1]	48,707,000	[1]
Derivative Liability, Notional Amount, Gross Basis	65,787,000	[1]	45,014,000	[1]	48,707,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	65,747,000		45,014,000		48,707,000
Derivative Asset, Fair Value, Net Asset	65,747,000	[3]	45,014,000	[3]	48,707,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	65,787,000		45,014,000		48,707,000
Derivative Liability, Fair Value, Net Liability	65,787,000	[3]	45,014,000	[3]	48,707,000	[3]
Equity Swap [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	198,518,000	[1]	160,535,000	[1]	144,289,000	[1]
Derivative Liability, Notional Amount, Gross Basis	186,192,000	[1]	160,535,000	[1]	144,289,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	10,645,000		16,247,000		9,151,000
Derivative Asset, Fair Value, Net Asset	10,645,000	[3]	16,247,000	[3]	9,151,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	10,645,000		16,247,000		9,151,000
Derivative Liability, Fair Value, Net Liability	10,645,000	[3]	16,247,000	[3]	9,151,000	[3]
Customer Derivative Before Cash Collateral [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	15,757,043,000	[1]	13,967,727,000	[1]	15,390,222,000	[1]
Derivative Liability, Notional Amount, Gross Basis	15,848,918,000	[1]	14,020,258,000	[1]	15,092,762,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	566,113,000		496,493,000		506,467,000
Derivative Asset, Fair Value, Net Asset	401,654,000	[3]	283,512,000	[3]	277,466,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	562,105,000		496,291,000		503,397,000
Derivative Liability, Fair Value, Net Liability	397,646,000	[3]	283,310,000	[3]	274,396,000	[3]
Cash Collateral [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	0	[1]	0	[1]	0	[1]
Derivative Liability, Notional Amount, Gross Basis	0	[1]	0	[1]	0	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	0		0		0
Derivative Asset, Fair Value, Net Asset	(37,298,000)	[3]	(15,017,000)	[3]	(19,907,000)	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	0		0		0
Derivative Liability, Fair Value, Net Liability	(55,824,000)	[3]	(68,987,000)	[3]	(56,157,000)	[3]
Total Customer Derivatives [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	15,757,043,000	[1]	13,967,727,000	[1]	15,390,222,000	[1]
Derivative Liability, Notional Amount, Gross Basis	15,848,918,000	[1]	14,020,258,000	[1]	15,092,762,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	566,113,000		496,493,000		506,467,000
Derivative Asset, Fair Value, Net Asset	364,356,000	[3]	268,495,000	[3]	257,559,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	562,105,000		496,291,000		503,397,000
Derivative Liability, Fair Value, Net Liability	341,822,000	[3]	214,323,000	[3]	218,239,000	[3]
Interest Rate Risk Management Program [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount, Gross Basis	44,000,000	[1]	124,000,000	[1]	124,000,000	[1]
Derivative Liability, Notional Amount, Gross Basis	0	[1]	17,977,000	[1]	2,977,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	6,260,000		1,950,000		8,545,000
Derivative Asset, Fair Value, Net Asset	6,260,000	[3]	1,950,000	[3]	8,545,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	0		1,097,000		57,000
Derivative Liability, Fair Value, Net Liability	$ 0	[3]	$ 1,097,000	[3]	$ 57,000	[3]

[1] Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.

[2] Includes interest rate swaps used by borrowers to modify interest rate terms of their loans and to be announced securities used by mortgage banking customers to hedge their loan production

[3] Derivative contracts are recorded on a net basis in the balance sheet in recognition of master netting agreements that enable the Company to settle all derivative positions with a given counterparty in total and to offset the net derivative position with the related cash collateral.