XML 67 R53.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Stock And Stock-Based Incentive Plans (Narrative) (Details) - USD ($) | 3 Months Ended |  |  |
--- | --- | --- | --- | ---
Aug. 31, 2016 | May 31, 2016 | Nov. 30, 2016 | Jun. 28, 2016 | Nov. 30, 2015
Stock and Stock-Based Incentive Plans |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost | $ 10,900,000 | $ 3,500,000 |  |  |
Share Repurchase Program |  |  |  |  |
Stock and Stock-Based Incentive Plans |  |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  | $ 4,550,000,000 |  |
Available for repurchase, as of end of period |  |  | $ 1,691,500,000 |  | $ 1,553,800,000
share repurchase program additional authorization [Member] |  |  |  |  |
Stock and Stock-Based Incentive Plans |  |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  | $ 750,000,000 |

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

X
- Definition An excess of the fair value of the modified award over the fair value of the award immediately before the modification. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPlanModificationIncrementalCompensationCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_AwardTypeAxis=kmx_ShareRepurchaseProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=kmx_SharerepurchaseprogramadditionalauthorizationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |