Intangible Assets, Net And Goodwill (Schedule Of Intangible Assets, Net And Goodwill) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 783,840	$ 797,964
Goodwill	1,715,263	1,715,714
Total Intangible assets, net and goodwill	2,499,103	2,513,678
Exchange And Clearing Organization Membership Interests And Registrations [Member]
Intangible Assets [Line Items]
Indefinite lived intangibles	8,702	9,041
Customer And Other Relationships [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	370,829	378,136
Intangibles, accumulated amortization	205,957	198,674
Trademarks And Tradename [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	305,355	309,382
Intangibles, accumulated amortization	82,681	78,778
Supply Contracts [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	93,524	95,733
Intangibles, accumulated amortization	50,076	47,867
Other Intangible Assets [Member]
Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	5,430	5,672
Intangibles, accumulated amortization	3,156	2,914
National Beef [Member]
Intangible Assets [Line Items]
Goodwill	14,991	14,991
Jefferies [Member]
Intangible Assets [Line Items]
Goodwill	1,696,413	1,696,864
Other Operations [Member]
Intangible Assets [Line Items]
Goodwill	$ 3,859	$ 3,859