Commitments, Contingencies and Guarantees - Credit Exposure from Loan Commitments (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	May 31, 2013
Offsetting [Abstract]
Corporate lending exposure carried at fair value included in financial instruments owned	$ 182.5
Corporate lending exposure carried at fair value included in financial instruments sold	$ 3.1

Corporate lending exposure carried at fair value included in financial instruments owned.

No definition available.

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