Derivatives, Derivatives Instruments Gain (Loss) in Income Statement (Details) (Not Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	$ 3,191	$ 544	$ 8,423	$ 8,544
Gain (Loss) on Derivatives, Net	(93)	31	1,706	(3,437)
To-be-announced residential mortgage-backed securities [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	(131)	(2,078)	(67)	(377)
Gain (Loss) on Derivatives, Net	0	0	0	0
Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	967	679	1,998	2,214
Gain (Loss) on Derivatives, Net	0	0	0	0
Energy contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	1,523	1,682	5,007	5,901
Gain (Loss) on Derivatives, Net	0	0	0	0
Agricultural contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	26	69	127	254
Gain (Loss) on Derivatives, Net	0	0	0	0
Foreign exchange contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	806	192	1,358	552
Gain (Loss) on Derivatives, Net	0	0	0	0
Equity option contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	0	0	0	0
Gain (Loss) on Derivatives, Net	0	0	0	0
Total customer risk management programs [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	3,191	544	8,423	8,544
Gain (Loss) on Derivatives, Net	0	0	0	0
Interest rate risk management programs [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	0	0	0	0
Gain (Loss) on Derivatives, Net	$ (93)	$ 31	$ 1,706	$ (3,437)