Derivatives, Derivatives Instruments Gain (Loss) in Income Statement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	$ 4,222	$ 1,146	$ 8,863	$ 2,273
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	2,345	1,225	(128)	(1,348)
TBA Residential Mortgage-Backed Securities Contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	186	(648)	1,307	(4,055)
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	0	0	0	0
Interest Rate Swap Contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	1,231	672	2,144	1,542
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	0	0	0	0
Energy Commodity [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	2,588	912	4,898	4,399
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	0	0	0	0
Agricultural Contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	92	92	183	160
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	0	0	0	0
Foreign Exchange [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	125	118	331	227
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	0	0	0	0
Equity Swap [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	0	0	0	0
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	0	0	0	0
Customer Derivative Trading [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	4,222	1,146	8,863	2,273
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	0	0	0	0
Interest Rate Risk Management Trading New [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Trading Activity, Gains and Losses, Net	0	0	0	0
Derivative Gain (Loss) on Derivative, Net [Abstract]
Gain (Loss) on Derivatives, Net	$ 2,345	$ 1,225	$ (128)	$ (1,348)