Variable Interest Entities - Variable Interests in Non-Consolidated Variable Interest Entities (Detail) - Variable Interest Entity Not Primary Beneficiary [Member] - USD ($) $ in Millions	May 31, 2017	Nov. 30, 2016
Variable Interest Entity [Line Items]
Carrying Amount, Assets	$ 256.1	$ 443.5
Carrying Amount, Liabilities	1.0	4.8
Maximum exposure to loss in non-consolidated VIEs	1,466.0	1,257.0
VIE Assets	7,859.9	9,467.5
Collateralized loan obligations [Member]
Variable Interest Entity [Line Items]
Carrying Amount, Assets	22.3	263.3
Carrying Amount, Liabilities	1.0	4.8
Maximum exposure to loss in non-consolidated VIEs	794.9	920.0
VIE Assets	2,834.5	4,451.7
Consumer Loan Vehicles [Member]
Variable Interest Entity [Line Items]
Carrying Amount, Assets	154.2	90.3
Carrying Amount, Liabilities	0.0	0.0
Maximum exposure to loss in non-consolidated VIEs	567.3	219.6
VIE Assets	1,533.7	985.5
Related party private equity vehicles [Member]
Variable Interest Entity [Line Items]
Carrying Amount, Assets	28.0	37.6
Carrying Amount, Liabilities	0.0	0.0
Maximum exposure to loss in non-consolidated VIEs	50.7	63.6
VIE Assets	103.2	155.6
Other private investment vehicles [Member]
Variable Interest Entity [Line Items]
Carrying Amount, Assets	51.6	52.3
Carrying Amount, Liabilities	0.0	0.0
Maximum exposure to loss in non-consolidated VIEs	53.1	53.8
VIE Assets	$ 3,388.5	$ 3,874.7

Variable Interest Entity Carrying Amount Of Assets Non Consolidated Vie

No definition available.

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

- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5728-111685

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64801991&loc=d3e5747-111685

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

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

- Definition

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

+ Details

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

- Definition

Carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=jef_ConsumerLoanFinancingVehiclesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=jef_PrivateEquityVehiclesMember
Namespace Prefix:
Data Type:	na
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- Details

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