Credit Facilities and Long-term Debt - Details of Financial Covenants (Details)	Dec. 31, 2019
Debt Disclosure [Abstract]
Current ratio, requirement	1.10
Current ratio	1.31
Fixed charge coverage ratio, requirement	1.20
Fixed charge coverage ratio	2.88
Leverage ratio, requirement	5.75
Leverage ratio	2.62

A ratio of current assets divided by current liabilities.

No definition available.

Name:	lad_CurrentRatio
Namespace Prefix:	lad_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

An ratio defined in the credit agreement as current assets divided by current liabilities. Under the credit agreement, the company is required to remain in compliance with this minimum current ratio.

+ References

No definition available.

+ Details

Name:	lad_DebtCovenantCurrentRatio
Namespace Prefix:	lad_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

A ratio defined in the credit agreement as fixed charges divided by earnings before interest, taxes, depreciation, amortization and rent (EBITDAR). Under the credit agreement, the company is required to remain in compliance with this minimum fixed charge coverage ratio.

+ References

No definition available.

+ Details

Name:	lad_DebtCovenantFixedChargeCoverageRatio
Namespace Prefix:	lad_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

A ratio defined in the credit agreement as funded debt divided by earnings before interest, taxes, depreciation, amortization and rent (EBITDAR). Under the credit agreement, the company is required to remain in compliance with this maximum leverage ratio.

+ References

No definition available.

+ Details

Name:	lad_DebtCovenantLeverageRatio
Namespace Prefix:	lad_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

A ratio defined in the credit agreement as fixed charges divided by earnings before interest, taxes, depreciation, amortization and rent (EBITDAR).

+ References

No definition available.

+ Details

Name:	lad_FixedChargeCoverageRatio
Namespace Prefix:	lad_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

A ratio defined in the credit agreement as funded debt divided by earnings before interest, taxes, depreciation, amortization and rent (EBITDAR).

+ References

No definition available.

+ Details

Name:	lad_LeverageRatio
Namespace Prefix:	lad_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

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