Increase (Decrease) of Long-term Debt

No definition available.

Name:	jef_IncreaseDecreaseofLongtermDebt
Namespace Prefix:	jef_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 944
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-Section S99
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-Name Accounting Standards Codification
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+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_DebtInstrumentAxis=jef_StructuredNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=jef_FourPointOneFiveZeroPercentSeniorNotesDue2030Member
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- Details

Name:	us-gaap_DebtInstrumentAxis=jef_FivePointOneTwoFivePercentageSeniorNotesDueTwoThousandEighteenMember
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
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Period Type:

Long-Term Debt - Additional Information (Detail) - USD ($)		6 Months Ended
	Nov. 22, 2017	May 31, 2018	May 31, 2017	May 16, 2018	Apr. 30, 2018	Nov. 30, 2017	Jan. 17, 2017
Debt Instrument [Line Items]
Long-term debt at fair value		$ 708,256,000				$ 606,956,000
Long-term debt		6,591,900,000				6,416,844,000
Redemption price as percentage of principal amount redeemed	100.00%
Unsecured Debt
Debt Instrument [Line Items]
Long-term debt		6,433,565,000				6,416,844,000
Senior Notes
Debt Instrument [Line Items]
Debt principal amount			$ 678,500,000
4.850% Senior Notes \| Unsecured Debt
Debt Instrument [Line Items]
Debt principal amount							$ 750,000,000
Long-term debt		$ 713,764,000				736,357,000
Debt instrument interest rate		4.85%
3.875% Convertible Senior Debentures
Debt Instrument [Line Items]
Debt principal amount		$ 345,000,000.0
Debt instrument interest rate		3.875%
3.875% Convertible Senior Debentures \| Unsecured Debt
Debt Instrument [Line Items]
Long-term debt		$ 0				324,779,000
Debt instrument interest rate		3.875%
Structured notes \| Unsecured Debt
Debt Instrument [Line Items]
Debt principal amount		$ 165,600,000	125,600,000
Long-term debt at fair value		708,300,000				607,000,000
Long-term debt		708,256,000				614,091,000
4.150% Senior Notes \| Unsecured Debt
Debt Instrument [Line Items]
Long-term debt		$ 987,365,000				0
Debt instrument interest rate		4.15%
4.150% Senior Notes \| Senior Notes
Debt Instrument [Line Items]
Debt principal amount		$ 1,000,000,000
Debt instrument interest rate		4.15%
5.125% Senior Notes \| Unsecured Debt
Debt Instrument [Line Items]
Long-term debt		$ 0			$ 668,300,000	682,338,000
Debt instrument interest rate		5.125%
Interest rate swaps \| 4.850% Senior Notes \| Unsecured Debt
Debt Instrument [Line Items]
Increase (decrease) of long-term debt		$ 22,800,000	$ (4,900,000)
Revolving Credit Facility \| Secured Debt
Debt Instrument [Line Items]
Debt principal amount				$ 160,000,000
Long-term debt		$ 158,335,000				$ 0