Variable Interest Entities - Schedule of Nonconsolidated VIEs (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Financial statement carrying amount, assets	$ 579.6	$ 566.9
Financial statement carrying amount, liabilities	8.9	4.8
Maximum Exposure to Loss	1,977.6	1,410.8
VIE Assets	12,386.9	10,229.3
CLOs
Variable Interest Entity [Line Items]
Financial statement carrying amount, assets	168.1	264.7
Financial statement carrying amount, liabilities	8.9	4.8
Maximum Exposure to Loss	1,030.4	930.0
VIE Assets	5,364.3	4,472.9
Consumer loan vehicles
Variable Interest Entity [Line Items]
Financial statement carrying amount, assets	254.8	90.3
Financial statement carrying amount, liabilities	0.0	0.0
Maximum Exposure to Loss	759.8	219.6
VIE Assets	2,322.7	985.5
Related party private equity vehicles
Variable Interest Entity [Line Items]
Financial statement carrying amount, assets	23.7	37.6
Financial statement carrying amount, liabilities	0.0	0.0
Maximum Exposure to Loss	45.4	63.6
VIE Assets	75.0	155.6
Real estate investment vehicles
Variable Interest Entity [Line Items]
Financial statement carrying amount, assets		90.3
Financial statement carrying amount, liabilities		0.0
Maximum Exposure to Loss		101.8
VIE Assets		85.6
Other private investment vehicles
Variable Interest Entity [Line Items]
Financial statement carrying amount, assets	133.0	84.0
Financial statement carrying amount, liabilities	0.0	0.0
Maximum Exposure to Loss	142.0	95.8
VIE Assets	$ 4,624.9	$ 4,529.7

Variable Interest Entity, Assets of Non Consolidated Vie

No definition available.

Name:	luk_VariableInterestEntityAssetsofNonConsolidatedVie
Namespace Prefix:	luk_
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

Name:	us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
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

Name:	us-gaap_VariableInterestEntityLineItems
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

Name:	us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
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

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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