Fair Value Disclosures - Investments Measured at Fair Value Based on Net Asset Value Per Share (Detail) - USD ($) $ in Thousands	9 Months Ended
Aug. 31, 2017	Nov. 30, 2016
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 194,107	$ 210,817
Unfunded Commitments	19,084	20,295
Equity Long/Short Hedge Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	34,931	34,446
Unfunded Commitments	$ 0	$ 0
Percentage of investment at fair value in liquidation	1.00%	2.00%
Fixed Income and High Yield Hedge Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 421	$ 772
Unfunded Commitments	0	0
Fund of Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	183	230
Unfunded Commitments	0	0
Private equity funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	33,568	42,179
Unfunded Commitments	$ 19,084	20,295
Estimated period for the liquidation of the underlying assets, minimum	1 year
Estimated period for the liquidation of the underlying assets, maximum	6 years
Multi-asset Funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 125,004	133,190
Unfunded Commitments	$ 0	$ 0
Percentage of redeemable investments	15.00%	12.00%
Multi-asset Funds \| Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Notice period redemption of investment prior written notice period	30 days
Multi-asset Funds \| Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Notice period redemption of investment prior written notice period	90 days

Estimated period for the liquidation of the underlying assets, maximum.

No definition available.

Name:	jef_EstimatedPeriodForLiquidationOfUnderlyingAssetsMaximum
Namespace Prefix:	jef_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated period for the liquidation of the underlying assets, Minimum.

+ References

No definition available.

+ Details

Name:	jef_EstimatedPeriodForLiquidationOfUnderlyingAssetsMinimum
Namespace Prefix:	jef_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Investments at fair value that cannot be redeemed at reporting date and are subject to a prior written redemption request.

+ References

No definition available.

+ Details

Name:	jef_NoticePeriodRedemptionOfInvestmentsPriorWrittenNoticePeriod
Namespace Prefix:	jef_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of Investment at Fair Value in Liquidation

+ References

No definition available.

+ Details

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

- Definition

Investments redeemable within 60-90 days

+ References

No definition available.

+ Details

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

- Definition

Fair value of investments in certain entities that calculate net asset value per share, including, but not limited to, by unit, membership interest, or other ownership interest. Investments include, but are not limited to, investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=SL6742756-110258

+ Details

Name:	us-gaap_AlternativeInvestmentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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

- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=SL6742756-110258

+ Details

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

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_HedgeFundsEquityLongShortMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=jef_HighYieldHedgeFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=jef_FundOfFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_PrivateEquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=jef_MultiassetFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: