Derivatives, Derivatives Instruments Gain (Loss) in Income Statement (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2020		Jun. 30, 2019
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	$ 38,819		$ 13,374		$ 1,386		$ 12,756
Gain (Loss) on Derivatives, Net	21,885		11,150		40,305		15,817
Total customer risk management programs
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	6,242		5,344		9,464		12,021
Gain (Loss) on Derivatives, Net	0		0		0		0
To-be-announced residential mortgage-backed securities [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	0		2,212		0		7,912
Gain (Loss) on Derivatives, Net	0		0		0		0
Interest rate contracts [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	746		942		1,688		1,535
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	5,383		2,086		7,390		2,312
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	6		4		21		8
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	107		100		365		254
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
Trading [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net [Abstract]
Brokergage and Trading Revenue	32,577	[1]	8,030	[1]	(8,078)	[2]	735	[2]
Gain (Loss) on Derivatives, Net	0	[1]	0	[1]	0	[2]	0	[2]
Internal 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	$ 21,885		$ 11,150		$ 40,305		$ 15,817

[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.

[2] 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.