Goodwill and Franchise Value (Schedule of Franchise Value) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2021	Dec. 31, 2020
Indefinite-lived Intangible Assets [Roll Forward]
Beginning balance	$ 350.2	$ 306.7
Additions through acquisitions	17.8	51.9
Reductions through divestitures	(0.1)	(4.0)
Reductions from impairments		(4.4)
Ending balance	$ 368.0	$ 350.2

Franchise Value, Impairment

No definition available.

Name:	lad_FranchiseValueImpairment
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying amount (original costs adjusted for previously recognized amortization and impairment) as of the balance sheet date for the rights acquired through a franchise arrangement having an indefinite period of benefit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of divestiture of an asset lacking physical substance and having a projected indefinite period of benefit to fair value. Excludes financial assets and goodwill.

+ References

No definition available.

+ Details

Name:	us-gaap_IndefiniteLivedIntangibleAssetsWrittenOffRelatedToSaleOfBusinessUnit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase in assets, excluding financial assets and goodwill, lacking physical substance with an indefinite life, from an acquisition.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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