Derivatives, Derivatives Instruments Gain (Loss) in Income Statement (Details) (Not Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	$ 12,380	$ 13,693	$ 5,314
Gain (Loss) on Derivatives, Net	(4,367)	(301)	2,526
To-be-announced residential mortgage-backed securities [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	42	1,070	(4,047)
Gain (Loss) on Derivatives, Net	0	0	0
Interest rate swaps [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	2,991	3,458	3,193
Gain (Loss) on Derivatives, Net	0	0	0
Energy contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	8,303	8,171	5,262
Gain (Loss) on Derivatives, Net	0	0	0
Agricultural contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	357	382	341
Gain (Loss) on Derivatives, Net	0	0	0
Foreign exchange contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	687	612	565
Gain (Loss) on Derivatives, Net	0	0	0
Equity option contracts [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	0	0	0
Gain (Loss) on Derivatives, Net	0	0	0
Customer risk management programs [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	12,380	13,693	5,314
Gain (Loss) on Derivatives, Net	0	0	0
Interest rate risk management program [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Brokergage and Trading Revenue	0	0	0
Gain (Loss) on Derivatives, Net	$ (4,367)	$ (301)	$ 2,526