Business Acquisition, Equity Interest Issued Or Issuable, Number Of Shares Per Common Stock Of Acquiree

No definition available.

Name:	jef_BusinessAcquisitionEquityInterestIssuedOrIssuableNumberOfSharesPerCommonStockOfAcquiree
Namespace Prefix:	jef_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Ownership Percentage

+ References

No definition available.

+ Details

Name:	jef_OwnershipPercentage
Namespace Prefix:	jef_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Ownership Percentage Upon Conversion of Preferred Shares

+ References

No definition available.

+ Details

Name:	jef_OwnershipPercentageUponConversionOfPreferredShares
Namespace Prefix:	jef_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=jef_NationalBeefMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=jef_SpectrumBrandsHoldingsInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=jef_LinkemMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=jef_WeWorkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=jef_HomefedCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=jef_JefferiesGroupLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=jef_NationalBeefMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsDisposedOfBySaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=jef_VitesseEnergyLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=jef_JETXEnergyLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=jef_HomefedCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Nature of Operations (Details) shares in Thousands, $ in Thousands		6 Months Ended		12 Months Ended
	Jul. 01, 2019 shares	May 31, 2019 USD ($) Segment	Jun. 30, 2018 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2019	Jul. 13, 2018	Jun. 05, 2018	Jun. 04, 2018
Schedule of Equity Method Investments [Line Items]
Number of business segments \| Segment		3
Payments to acquire investments \| $		$ 1,986	$ 1,961,344
National Beef
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		31.00%					31.00%
Ownership percentage								79.00%
Spectrum Brands
Schedule of Equity Method Investments [Line Items]
Ownership percentage		15.00%				14.00%
Linkem
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		42.00%
Percentage of ownership upon conversion of preferred shares		54.00%
WeWork
Schedule of Equity Method Investments [Line Items]
Payments to acquire investments \| $				$ 9,000
HomeFed
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		70.00%
Jefferies Group
Schedule of Equity Method Investments [Line Items]
Number of business segments \| Segment		2
National Beef \| Discontinued operations, disposed of by sale
Schedule of Equity Method Investments [Line Items]
Ownership percentage							48.00%
Maximum \| WeWork
Schedule of Equity Method Investments [Line Items]
Ownership percentage		1.00%
Vitesse Energy, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage		97.00%
JETX Energy
Schedule of Equity Method Investments [Line Items]
Ownership percentage		98.00%
Subsequent Event
Schedule of Equity Method Investments [Line Items]
Number of shares authorized to be repurchased \| shares	9,250
Subsequent Event \| HomeFed
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage					70.00%
Number of shares issued per common stock of acquiree	2
Subsequent Event \| HomeFed
Schedule of Equity Method Investments [Line Items]
Number of shares issued \| shares	9,300