Name:	an_CreditSpreadImpactLeverageRatioCreditAgreement
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Data Type:	num:percentItemType
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The minimum, inclusive, leverage ratio, as defined in the credit agreement, in which the credit spread on the revolver would increase based on the pricing terms outlined in the agreement.

No definition available.

Name:	an_DebtCovenantIncreaseinLeverageRatioMinimumBenchmarkRange
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Data Type:	xbrli:pureItemType
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The maximum, exclusive, leverage ratio, as defined in the credit agreement, in which the current credit spread on the revolver applies based on pricing terms outlined in the credit agreement.

No definition available.

Name:	an_DebtCovenantMaximumExclusiveRangeLeverageRatioCreditSpread
Namespace Prefix:	an_
Data Type:	xbrli:pureItemType
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The minimum, inclusive, leverage ratio, as defined in the credit agreement, in which the current credit spread on the revolver applies based on pricing terms outlined in the agreement.

No definition available.

Name:	an_DebtCovenantMinimumInclusiveRangeLeverageRatioCreditSpread
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Data Type:	xbrli:pureItemType
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Maximum amount of increase in the revolving credit facility allowed under the accordion feature of the credit agreement, subject to credit availability and certain other conditions.

No definition available.

Name:	an_LineofCreditFacilityAdditionalBorrowingCapacity
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of current borrowing capacity under the revolving credit facility considering any current restrictions on the amount that could be borrowed and any amounts currently outstanding under the facility.

No definition available.

Name:	an_LineofCreditRestrictedBorrowingCapacity
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Data Type:	xbrli:monetaryItemType
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The maximum amount of letters of credit that can be issued under the terms of the revolving credit facilities.

No definition available.

Name:	an_RevolvingCreditFacilitiesLetterOfCreditSublimit
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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

No definition available.

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	num:percentItemType
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Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

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

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

No definition available.

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

The cash outflow for the settlement of long-term borrowing, with the highest claim on the assets of the entity in case of bankruptcy or liquidation, as it matures.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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Data Type:	xbrli:monetaryItemType
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Name:	us-gaap_DebtInstrumentAxis=an_SeniorNotesatThreePointThreeFivePercentDue2021Member
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Name:	us-gaap_DebtInstrumentAxis=an_SeniorNotesatThreePointFivePercentDue2024Member
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