Intangible Assets, Net And Goodwill (Schedule Of Intangible Assets, Net And Goodwill) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 893,051	$ 912,021
Goodwill	1,729,300	1,736,341
Total Intangible assets, net and goodwill	2,622,351	2,648,362
Exchange And Clearing Organization Membership Interests And Registrations [Member]
Intangible Assets [Line Items]
Indefinite lived intangibles	10,550	11,897
Customer And Other Relationships [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	446,849	456,222
Intangibles, accumulated amortization	200,287	191,761
Trademarks And Tradename [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	324,639	330,172
Intangibles, accumulated amortization	68,147	64,052
Supply Contracts [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	106,795	109,311
Intangibles, accumulated amortization	43,200	40,684
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	4,218	4,419
Intangibles, accumulated amortization	5,417	5,216
National Beef [Member]
Intangible Assets [Line Items]
Goodwill	14,991	14,991
Jefferies [Member]
Intangible Assets [Line Items]
Goodwill	1,705,758	1,712,799
Other Operations [Member]
Intangible Assets [Line Items]
Goodwill	$ 8,551	$ 8,551