Derivatives, Fair Value of Derivatives Contracts (Details) (USD $)	Dec. 31, 2012		Dec. 31, 2011
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Net Asset	$ 338,106,000		$ 293,859,000
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Net Liability	283,589,000		236,522,000
Increase in cash margin obligation for derivative holdings with a decrease in credit rating from A1 to below investment grade	35,000,000
Not Designated as Hedging Instrument [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	16,188,105,000	[1]	12,417,696,000	[1]
Derivative Liability, Notional Amount	16,547,182,000	[1]	12,579,110,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	404,875,000		437,878,000
Derivative Asset, Fair Value, Net Asset	338,106,000	[2]	293,859,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	396,263,000		442,563,000
Derivative Liability, Fair Value, Net Liability	283,589,000	[2]	236,522,000	[3]
Not Designated as Hedging Instrument [Member] | TBA Residential Mortgage-Backed Securities Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	12,850,805,000	[1],[4]	9,118,627,000	[1],[4]
Derivative Liability, Notional Amount	13,239,078,000	[1],[4]	9,051,627,000	[1],[4]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	46,113,000	[4]	101,189,000	[4]
Derivative Asset, Fair Value, Net Asset	30,457,000	[2],[4]	68,519,000	[3],[4]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	43,064,000	[4]	99,211,000	[4]
Derivative Liability, Fair Value, Net Liability	27,408,000	[2],[4]	66,541,000	[3],[4]
Not Designated as Hedging Instrument [Member] | Interest Rate Swap Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	1,319,827,000	[1],[4]	1,272,617,000	[1],[4]
Derivative Liability, Notional Amount	1,319,827,000	[1],[4]	1,272,617,000	[1],[4]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	72,201,000	[4]	81,261,000	[4]
Derivative Asset, Fair Value, Net Asset	72,201,000	[2],[4]	81,261,000	[3],[4]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	72,724,000	[4]	81,891,000	[4]
Derivative Liability, Fair Value, Net Liability	72,724,000	[2],[4]	81,891,000	[3],[4]
Not Designated as Hedging Instrument [Member] | Energy Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	1,346,780,000	[1]	1,554,400,000	[1]
Derivative Liability, Notional Amount	1,334,349,000	[1]	1,799,367,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	82,349,000		158,625,000
Derivative Asset, Fair Value, Net Asset	37,864,000	[2]	62,945,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	83,654,000		171,050,000
Derivative Liability, Fair Value, Net Liability	39,169,000	[2]	75,370,000	[3]
Not Designated as Hedging Instrument [Member] | Agriculture Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	212,434,000	[1]	146,252,000	[1]
Derivative Liability, Notional Amount	212,135,000	[1]	148,924,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	3,638,000		4,761,000
Derivative Asset, Fair Value, Net Asset	474,000	[2]	782,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	3,571,000		4,680,000
Derivative Liability, Fair Value, Net Liability	407,000	[2]	701,000	[3]
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	180,318,000	[1]	73,153,000	[1]
Derivative Liability, Notional Amount	179,852,000	[1]	72,928,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	180,318,000		73,153,000
Derivative Asset, Fair Value, Net Asset	180,318,000	[2]	73,153,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	179,852,000		72,928,000
Derivative Liability, Fair Value, Net Liability	179,852,000	[2]	72,928,000	[3]
Not Designated as Hedging Instrument [Member] | Equity Swap Contracts [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	211,941,000	[1]	208,647,000	[1]
Derivative Liability, Notional Amount	211,941,000	[1]	208,647,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	12,593,000		12,508,000
Derivative Asset, Fair Value, Net Asset	12,593,000	[2]	12,508,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	12,593,000		12,508,000
Derivative Liability, Fair Value, Net Liability	12,593,000	[2]	12,508,000	[3]
Not Designated as Hedging Instrument [Member] | Customer Derivatives Before Cash Collateral [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	16,122,105,000	[1]	12,373,696,000	[1]
Derivative Liability, Notional Amount	16,497,182,000	[1]	12,554,110,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	397,212,000		431,497,000
Derivative Asset, Fair Value, Net Asset	333,907,000	[2]	299,168,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	395,458,000		442,268,000
Derivative Liability, Fair Value, Net Liability	332,153,000	[2]	309,939,000	[3]
Not Designated as Hedging Instrument [Member] | Cash Collateral [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	0	[1]	0	[1]
Derivative Liability, Notional Amount	0	[1]	0	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Asset, Fair Value, Net Asset	(3,464,000)	[2]	(11,690,000)	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	0		0
Derivative Liability, Fair Value, Net Liability	(49,369,000)	[2]	(73,712,000)	[3]
Not Designated as Hedging Instrument [Member] | Total Customer Derivatives [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	16,122,105,000	[1]	12,373,696,000	[1]
Derivative Liability, Notional Amount	16,497,182,000	[1]	12,554,110,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	397,212,000		431,497,000
Derivative Asset, Fair Value, Net Asset	330,443,000	[2]	287,478,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	395,458,000		442,268,000
Derivative Liability, Fair Value, Net Liability	282,784,000	[2]	236,227,000	[3]
Not Designated as Hedging Instrument [Member] | Interest Rate Risk Management Program [Member]
Notional Amount of Derivatives [Abstract]
Derivative Asset, Notional Amount	66,000,000	[1]	44,000,000	[1]
Derivative Liability, Notional Amount	50,000,000	[1]	25,000,000	[1]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset	7,663,000		6,381,000
Derivative Asset, Fair Value, Net Asset	7,663,000	[2]	6,381,000	[3]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	805,000		295,000
Derivative Liability, Fair Value, Net Liability	805,000	[2]	295,000	[3]
Change in the fair value of mortgage servicing rights [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Risk Management Program [Member]
Notional Amount of Derivatives [Abstract]
Residential Mortgage Derivatives Notional Amount	$ 91,000,000	[1]

[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] 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.

[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.