Debt Instrument, Redemption Price, Percentage Of Principal Amount Redeemable

No definition available.

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- Definition

The amount of notes payable attributable to the floor plan.

+ References

No definition available.

+ Details

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

- Definition

Line Of Credit Facility, Accordion Feature, Higher Borrowing Capacity Option

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum amount on the revolving loan of credit availability that would be reserved and used to repay outstanding balances on the new vehicle floor plan commitment.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of financial institutions.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of manufacturer affiliated finance companies.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The fixed interest rate percentage on total mortgage debt.

+ References

No definition available.

+ Details

Name:	lad_PercentOfTotalMortgageDebtThatIsFixed
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The maximum deposit amount for principal reduction accounts.

+ References

No definition available.

+ Details

Name:	lad_PrincipalReductionAccountsMaximumDepositAmount
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The outstanding amount for principal reduction accounts.

+ References

No definition available.

+ Details

Name:	lad_PrincipalReductionAccountsOutstandingAmount
Namespace Prefix:	lad_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The reserve commitment expressed as a percentage.

+ References

No definition available.

+ Details

Name:	lad_ReserveCommitmentPercent
Namespace Prefix:	lad_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
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

+ 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
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

+ Details

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

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Details

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- Details

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- Details

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Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_DebtInstrumentAxis=lad_SyndicatedCreditFacilityMember
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- Details

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- Details

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- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
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Balance Type:
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- Details

Name:	us-gaap_DebtInstrumentAxis=lad_SeniorNotesDue2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=lad_NewVehicleFloorPlanMember
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Data Type:	na
Balance Type:
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- Details

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- Details

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- Details

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- Details

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Credit Facilities and Long-term Debt (Narrative) (Details)		12 Months Ended
	Jul. 24, 2017 USD ($)	Dec. 31, 2017 USD ($)	Aug. 01, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Floor plan notes payable		$ 116,774,000		$ 94,602,000
Total long-term debt outstanding		$ 1,054,271,000		793,065,000
Floor Plan Notes Payable \| Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		5.50%
Line of Credit
Debt Instrument [Line Items]
Principal reduction accounts, maximum deposit		$ 50,000,000
Principal reduction accounts, outstanding balance		$ 0
Line of Credit \| Credit Facility
Debt Instrument [Line Items]
Total financing commitment			$ 2,400,000,000
Number of financial institutions			18
Number of manufacturer affiliated finance companies			7
Higher borrowing capacity option			$ 2,750,000,000
Real Estate Mortgages
Debt Instrument [Line Items]
Percent of total mortgage debt that is fixed		78.90%
Total long-term debt outstanding		$ 469,969,000		428,367,000
Real Estate Mortgages \| Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		2.80%
Real Estate Mortgages \| Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		5.00%
Capital Lease Obligations
Debt Instrument [Line Items]
Total long-term debt outstanding		$ 12,512,000		11,191,000
Capital Lease Obligations \| Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		3.10%
Capital Lease Obligations \| Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		8.00%
Senior Notes \| 5.25% Senior notes due 2025
Debt Instrument [Line Items]
Interest rate, stated percentage	5.25%
Total long-term debt outstanding	$ 300,000,000	$ 300,000,000		0
Redemption percentage price (percent)	100.00%
Percentage of principal amount redeemable (percent)	101.00%
New vehicle floor plan \| Line of Credit
Debt Instrument [Line Items]
Reserve commitment (in percent)		95.00%
Reserve amount requirement		$ 15,000,000
Annual interest rate (in percent)		2.82%
New vehicle floor plan \| Line of Credit \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.25%
New vehicle floor plan \| Line of Credit \| Credit Facility
Debt Instrument [Line Items]
Total financing commitment			1,900,000,000
Used vehicle inventory financing facility \| Line of Credit
Debt Instrument [Line Items]
Annual interest rate (in percent)		3.07%
Total long-term debt outstanding		$ 177,222,000		211,000,000
Used vehicle inventory financing facility \| Line of Credit \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.50%
Used vehicle inventory financing facility \| Line of Credit \| Credit Facility
Debt Instrument [Line Items]
Total financing commitment			$ 500,000,000
Revolving lines of credit \| Line of Credit
Debt Instrument [Line Items]
Annual interest rate (in percent)		3.07%
Total long-term debt outstanding		$ 94,568,000		$ 142,507,000
Revolving lines of credit \| Line of Credit \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.25%
Revolving lines of credit \| Line of Credit \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		2.50%
Other lines of credit
Debt Instrument [Line Items]
Total financing commitment		$ 3,500,000
Long-term line of credit		$ 600,000
Other lines of credit \| Maximum
Debt Instrument [Line Items]
Annual interest rate (in percent)		2.94%