Derivative Financial Instruments (Counterparty Credit Quality With Respect To Fair Value Of OTC Derivatives Assets) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Derivative Financial Instruments [Abstract]
Fair value of OTC derivatives assets, Counterparty credit quality, A- or higher	$ 232,256	[1]
Fair value of OTC derivatives assets, Counterparty credit quality, BBB- to BBB+	34,697	[1]
Fair value of OTC derivatives assets, Counterparty credit quality, BB+ or lower	54,576	[1]
Fair value of OTC derivatives assets, Counterparty credit quality, Unrated	19,412	[1]
Fair value of Over the Counter Derivatives Assets Counterparty credit quality	$ 340,941	[1],[2],[3],[4]

[1] We utilize the credit ratings of external rating agencies when available. When external credit ratings are not available, we utilize internal credit ratings determined by Jefferies Risk Management. Credit ratings determined by Risk Management use methodologies that produce ratings generally consistent with those produced by external rating agencies.

[2] At June 30, 2013, we held exchange traded derivative assets and other credit agreements with a fair value of $16.8 million, which are not included in this table.

[3] OTC derivative assets in the table above are gross of collateral received. OTC derivative assets are recorded net of collateral received in the Consolidated Statements of Financial Condition. At June 30, 2013 cash collateral received was $164.9 million.

[4] Derivative fair values include counterparty netting within product category.