Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_Assets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

+ Details

Name:	us-gaap_DeferredIncomeTaxAssetsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

+ Details

Name:	us-gaap_DepreciationDepletionAndAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68072869&loc=d3e41242-110953

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

+ Details

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

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income after deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

No definition available.

+ Details

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

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidationItemsAxis=srt_ConsolidationEliminationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jef_InvestmentBankingAndCapitalMarketsSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jef_AssetManagementSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jef_MerchantBankingSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_CorporateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Segment Information - Schedule of Segment Reporting Information By Segment (Details) - USD ($) $ in Thousands	2 Months Ended	3 Months Ended							11 Months Ended		12 Months Ended
	Nov. 30, 2018	Nov. 30, 2019	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2019	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net revenues	$ 806,594	$ 1,106,098	$ 856,778	$ 1,101,657	$ 828,443	$ 1,150,846	$ 911,159	$ 895,435	$ 3,764,034	$ 4,031,333	$ 3,892,976	$ 4,077,445
Income from continuing operations before income taxes									296,100	$ 618,110	478,608	606,502
Depreciation and amortization									120,317		152,871	110,395
Identifiable assets employed	47,131,095	49,460,234							47,131,095		49,460,234	47,169,108
Deferred tax asset, net	512,789	462,468							512,789		462,468
Parent Company interest
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes									(54,090)		(53,048)	(58,943)
Leucadia Asset Management and Berkadia Transferred
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes									78,700			91,500
Identifiable assets employed												212,400
Reportable Segments
Segment Reporting Information [Line Items]
Net revenues									3,769,724		3,888,928	4,068,457
Income from continuing operations before income taxes									354,015		526,949	654,495
Identifiable assets employed	47,253,428	49,554,729							47,253,428		49,554,729	47,239,429
Consolidation adjustments
Segment Reporting Information [Line Items]
Net revenues									(5,690)		4,048	8,988
Income from continuing operations before income taxes									(3,825)		4,707	10,950
Identifiable assets employed	(122,333)	(94,495)							(122,333)		(94,495)	(70,321)
Investment Banking and Capital Markets \| Reportable Segments
Segment Reporting Information [Line Items]
Net revenues									3,184,426		3,035,988	3,169,860
Income from continuing operations before income taxes									464,913		347,050	535,801
Depreciation and amortization									67,467		77,549	62,059
Identifiable assets employed	38,617,201	40,523,223							38,617,201		40,523,223	38,376,686
Deferred tax asset, net	243,200	197,700							243,200		197,700	213,000
Asset Management \| Reportable Segments
Segment Reporting Information [Line Items]
Net revenues									(14,280)		84,894	91,101
Income from continuing operations before income taxes									(133,729)		(41,126)	121
Depreciation and amortization									1,324		2,042	1,217
Identifiable assets employed	2,633,585	3,313,716							2,633,585		3,313,716	2,083,174
Merchant Banking \| Reportable Segments
Segment Reporting Information [Line Items]
Net revenues									577,278		735,213	801,190
Income from continuing operations before income taxes									88,971		289,492	197,375
Depreciation and amortization									48,357		69,805	43,649
Identifiable assets employed	4,164,605	3,285,671							4,164,605		3,285,671	4,019,402
National Beef \| Reportable Segments
Segment Reporting Information [Line Items]
Identifiable assets employed	0	0							0		0	1,460,539
Corporate \| Reportable Segments
Segment Reporting Information [Line Items]
Net revenues									22,300		32,833	6,306
Income from continuing operations before income taxes									(66,140)		(68,467)	(78,802)
Depreciation and amortization									3,169		3,475	3,470
Identifiable assets employed	$ 1,838,037	$ 2,432,119							$ 1,838,037		$ 2,432,119	$ 1,299,628