Derivatives, Fair Value of Derivatives Contracts (Details) (USD $)	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2011
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	$ 17,225,157,000	[1]	$ 12,417,696,000	[1]	$ 10,605,839,000	[1]
Derivative Liability, Notional Amount	17,023,801,000	[1]	12,579,110,000	[1]	10,584,538,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	534,862,000		437,878,000		379,296,000
Derivative Asset, Fair Value, Net Asset	366,204,000	[2],[3]	293,859,000	[2],[3]	229,887,000	[2],[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	530,648,000		442,563,000		374,177,000
Derivative Liability, Fair Value, Net Liability	370,053,000	[2],[3]	236,522,000	[2],[3]	173,917,000	[2],[3]
Increase in cash margin obligation for derivative holdings with a decrease in credit rating from A1 to below investment grade	38,000,000
TBA Residential Mortgage-Backed Securities Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	13,724,514,000	[1],[4]	9,118,627,000	[1],[4]	7,060,740,000	[1],[4]
Derivative Liability, Notional Amount	13,579,184,000	[1],[4]	9,051,627,000	[1],[4]	6,899,052,000	[1],[4]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	144,158,000	[4]	101,189,000	[4]	51,503,000	[4]
Derivative Asset, Fair Value, Net Asset	104,781,000	[2],[4]	68,519,000	[2],[4]	27,997,000	[2],[4]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	140,873,000	[4]	99,211,000	[4]	49,483,000	[4]
Derivative Liability, Fair Value, Net Liability	101,496,000	[2],[4]	66,541,000	[2],[4]	25,977,000	[2],[4]
Interest Rate Swap Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	1,271,138,000	[1],[4]	1,272,617,000	[1],[4]	1,197,499,000	[1],[4]
Derivative Liability, Notional Amount	1,271,138,000	[1],[4]	1,272,617,000	[1],[4]	1,197,499,000	[1],[4]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	77,121,000	[4]	81,261,000	[4]	64,051,000	[4]
Derivative Asset, Fair Value, Net Asset	77,121,000	[2],[4]	81,261,000	[2],[4]	63,442,000	[2],[4]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	77,671,000	[4]	81,891,000	[4]	64,051,000	[4]
Derivative Liability, Fair Value, Net Liability	77,671,000	[2],[4]	81,891,000	[2],[4]	64,051,000	[2],[4]
Energy Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	1,667,819,000	[1]	1,554,400,000	[1]	1,917,521,000	[1]
Derivative Liability, Notional Amount	1,653,592,000	[1]	1,799,367,000	[1]	2,094,878,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	150,754,000		158,625,000		158,922,000
Derivative Asset, Fair Value, Net Asset	75,625,000	[2]	62,945,000	[2]	51,820,000	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	156,690,000		171,050,000		157,998,000
Derivative Liability, Fair Value, Net Liability	81,561,000	[2]	75,370,000	[2]	50,896,000	[2]
Agriculture Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	140,722,000	[1]	146,252,000	[1]	125,644,000	[1]
Derivative Liability, Notional Amount	140,255,000	[1]	148,924,000	[1]	132,573,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	4,655,000		4,761,000		6,025,000
Derivative Asset, Fair Value, Net Asset	1,125,000	[2]	782,000	[2]	1,847,000	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	4,604,000		4,680,000		5,961,000
Derivative Liability, Fair Value, Net Liability	1,074,000	[2]	701,000	[2]	1,783,000	[2]
Foreign Exchange Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	136,815,000	[1]	73,153,000	[1]	78,471,000	[1]
Derivative Liability, Notional Amount	136,483,000	[1]	72,928,000	[1]	78,572,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	136,815,000		73,153,000		78,471,000
Derivative Asset, Fair Value, Net Asset	136,815,000	[2]	73,153,000	[2]	78,471,000	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	136,483,000		72,928,000		78,572,000
Derivative Liability, Fair Value, Net Liability	136,483,000	[2]	72,928,000	[2]	78,572,000	[2]
Equity Swap Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	218,149,000	[1]	208,647,000	[1]	181,964,000	[1]
Derivative Liability, Notional Amount	218,149,000	[1]	208,647,000	[1]	181,964,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	13,726,000		12,508,000		18,112,000
Derivative Asset, Fair Value, Net Asset	13,726,000	[2]	12,508,000	[2]	18,112,000	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	13,726,000		12,508,000		18,112,000
Derivative Liability, Fair Value, Net Liability	13,726,000	[2]	12,508,000	[2]	18,112,000	[2]
Customer Derivatives Before Cash Collateral [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	17,159,157,000	[1]	12,373,696,000	[1]	10,561,839,000	[1]
Derivative Liability, Notional Amount	16,998,801,000	[1]	12,554,110,000	[1]	10,584,538,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	527,229,000		431,497,000		377,084,000
Derivative Asset, Fair Value, Net Asset	409,193,000	[2]	299,168,000	[2]	241,689,000	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	530,047,000		442,268,000		374,177,000
Derivative Liability, Fair Value, Net Liability	412,011,000	[2]	309,939,000	[2]	239,391,000	[2]
Cash Collateral [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	0	[1]	0	[1]	0	[1]
Derivative Liability, Notional Amount	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	(50,622,000)	[2]	(11,690,000)	[2]	(14,014,000)	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	0		0		0
Derivative Liability, Fair Value, Net Liability	(42,559,000)	[2]	(73,712,000)	[2]	(65,474,000)	[2]
Total Customer Derivatives [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	17,159,157,000	[1]	12,373,696,000	[1]	10,561,839,000	[1]
Derivative Liability, Notional Amount	16,998,801,000	[1]	12,554,110,000	[1]	10,584,538,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	527,229,000		431,497,000		377,084,000
Derivative Asset, Fair Value, Net Asset	358,571,000	[2]	287,478,000	[2]	227,675,000	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	530,047,000		442,268,000		374,177,000
Derivative Liability, Fair Value, Net Liability	369,452,000	[2]	236,227,000	[2]	173,917,000	[2]
Interest Rate Risk Management Program [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	66,000,000	[1]	44,000,000	[1]	44,000,000	[1]
Derivative Liability, Notional Amount	25,000,000	[1]	25,000,000	[1]	0	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	7,633,000		6,381,000		2,212,000
Derivative Asset, Fair Value, Net Asset	7,633,000	[2]	6,381,000	[2]	2,212,000	[2]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	601,000		295,000		0
Derivative Liability, Fair Value, Net Liability	$ 601,000	[2]	$ 295,000	[2]	$ 0	[2]

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

[2] 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.

[3] See Note 3 for detail of fair value of derivative contracts by contract type.

[4] 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.