Derivatives, Derivatives Instruments Gain (Loss) in Income Statement (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		$ (37,433)	$ (618)
Gain (Loss) on Derivatives, Net		18,420	4,667
Total customer risk management programs
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		3,222	6,677
Gain (Loss) on Derivatives, Net		0	0
To-be-announced residential mortgage-backed securities [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		0	5,700
Gain (Loss) on Derivatives, Net		0	0
Interest rate contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		942	593
Gain (Loss) on Derivatives, Net		0	0
Energy contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		2,007	226
Gain (Loss) on Derivatives, Net		0	0
Agricultural contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		15	4
Gain (Loss) on Derivatives, Net		0	0
Foreign exchange contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		258	154
Gain (Loss) on Derivatives, Net		0	0
Equity option contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		0	0
Gain (Loss) on Derivatives, Net		0	0
Trading [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	[1]	(40,655)	(7,295)
Gain (Loss) on Derivatives, Net	[1]	0	0
Internal risk management programs [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue		0	0
Gain (Loss) on Derivatives, Net		$ 18,420	$ 4,667

[1] Represents changes in fair value of to-be-announced securities and other derivative instruments held to mitigate market risk of trading securities portfolio, which is offset by changes in fair value of trading securities also include in Brokerage and Trading Revenue in the Consolidated Statements of Earnings.