XML 43 R32.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Background (Narrative) (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
May 31, 2018 USD ($) segment | May 31, 2017 USD ($) | Mar. 01, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |  |
Reportable segments | segment | 2 |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  | $ 12.9
Other Sales |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | $ 4.0 |  |
Other Current Assets |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | 13.8 |  |
Accrued expenses and other current liabilities |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | 13.8 |  |
Investing Activities [Member] |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification |  | $ 10.1 |
Minimum | Accounting Standards Update 2016-02 |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | 400.0 |  |
Maximum | Accounting Standards Update 2016-02 |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | $ 430.0 |  |

X
- Definition Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
Name: | us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the quantification of the effect of adopting the new accounting standard or change in accounting principle expected by the entity to have a significant effect on the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfAdoptionQuantification
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References No definition available. + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=kmx_OtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | kmx_CashFlowLocationAxis=kmx_InvestingActivitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | kmx_EstimatedImpactofNewAccountingPronouncementsAxisAxis=us-gaap_AccountingStandardsUpdate201602Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |