Commitments and Contingencies - Lifetime Lube, Oil and Filter Contracts Acquired (Details) - Lifetime Oil Contracts $ in Thousands	Dec. 31, 2017 USD ($)
Product Information [Line Items]
2018	$ 25,212
2019	20,048
2020	15,913
2021	13,292
2022	11,368
Thereafter	41,424
Total	$ 127,257

Amount of deferred revenue to be recognized in the next fiscal year following the latest fiscal year.

No definition available.

Name:	lad_DeferredRevenueRecognizableCurrent
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred revenue to be recognized in the fifth year following the latest fiscal year

+ References

No definition available.

+ Details

Name:	lad_DeferredRevenueRecognizableInYearFive
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred revenue to be recognized in the fourth year following the latest fiscal year.

+ References

No definition available.

+ Details

Name:	lad_DeferredRevenueRecognizableInYearFour
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred revenue to be recognized in the third year following the latest fiscal year.

+ References

No definition available.

+ Details

Name:	lad_DeferredRevenueRecognizableInYearThree
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred revenue to be recognized in the second year following the latest fiscal year.

+ References

No definition available.

+ Details

Name:	lad_DeferredRevenueRecognizableInYearTwo
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred revenue to be recognized after the fifth year following the latest fiscal year.

+ References

No definition available.

+ Details

Name:	lad_DeferredRevenueRecognizableThereafter
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 13.A.3)
-URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 605
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 13.A.4(a).Q1)
-URI http://asc.fasb.org/extlink&oid=65893310&loc=d3e214044-122780

+ Details

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

- Details

Name:	us-gaap_ProductOrServiceAxis=lad_LifetimeOilContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: