Derivative Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Nov. 30, 2011
Counterparty credit quality:
Fair value of OTC derivatives assets, Counterparty credit quality, A or higher	$ 267,265
Fair value of OTC derivatives assets, Counterparty credit quality, B to BBB	252,484
Fair value of OTC derivatives assets counterparty credit quality, Lower than B	206
Fair Value of OTC derivatives assets Counterparty credit quality, Unrated	6,279
Fair Value of Over the Counter Derivatives Assets Counterparty credit quality	$ 526,234

Name:	jef_DerivativeFairValueOfDerivativeAssetCounterpartyCreditQualityAbstract
Namespace Prefix:	jef_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair value of over the counter derivatives assets, counterparty credit quality.

No definition available.

Name:	jef_FairValueOfOverCounterDerivativesAssetsCounterpartyCreditQuality
Namespace Prefix:	jef_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair value of over counter derivatives assets counterparty credit quality B to BBB.

No definition available.

Name:	jef_FairValueOfOverCounterDerivativesAssetsCounterpartyCreditQualityBToBbb
Namespace Prefix:	jef_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair value of over counter derivatives assets counterparty credit quality lower than b.

No definition available.

Name:	jef_FairValueOfOverCounterDerivativesAssetsCounterpartyCreditQualityLowerThanB
Namespace Prefix:	jef_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair value of Over The Counter derivatives assets, counterparty credit quality, A or higher.

No definition available.

Name:	jef_FairValueOfOverCounterDerivativesAssetsCounterpartyCreditQualityOrHigher
Namespace Prefix:	jef_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair value of over the counter derivatives assets, counterparty credit quality, unrated.

No definition available.

Name:	jef_FairValueOfOverCounterDerivativesAssetsCounterpartyCreditQualityUnrated
Namespace Prefix:	jef_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant