Derivatives, Derivatives Instruments Gain (Loss) in Income Statement (Details) (Not Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	$ 2,831	$ 4,641
Gain (Loss) on Derivatives, Net	6,118	(2,473)
TBA Residential Mortgage-Backed Securities Contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	(15)	1,122
Gain (Loss) on Derivatives, Net	0	0
Interest Rate Swap Contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	767	912
Gain (Loss) on Derivatives, Net	0	0
Energy Commodity [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	1,783	2,310
Gain (Loss) on Derivatives, Net	0	0
Agricultural Contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	108	91
Gain (Loss) on Derivatives, Net	0	0
Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	188	206
Gain (Loss) on Derivatives, Net	0	0
Equity Option [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	0	0
Gain (Loss) on Derivatives, Net	0	0
Customer Risk Management Programs [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	2,831	4,641
Gain (Loss) on Derivatives, Net	0	0
Interest Rate Risk Management Programs [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	0	0
Gain (Loss) on Derivatives, Net	$ 6,118	$ (2,473)