Initial Lease Terms.

No definition available.

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Balance Type:	na
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- Definition

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

+ References

No definition available.

+ Details

Name:	kmx_WarehouseFacilitiesMaximumBorrowingCapacity
Namespace Prefix:	kmx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of total borrowing capacity currently available under the warehouse facilities (current borrowing capacity less the amount of borrowings outstanding).

+ References

No definition available.

+ Details

Name:	kmx_WarehouseFacilitiesRemainingBorrowingCapacity
Namespace Prefix:	kmx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

+ 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(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of cash paid during the current period for interest that is capitalized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

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

+ 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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: 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(a)(16))
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+ Details

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

- Definition

Amount of debt for which creditor does not have general recourse to the debtor but rather has recourse only to the property used for collateral in the transaction or other specific property.

+ References

No definition available.

+ Details

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

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Balance Type:
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- Details

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Balance Type:
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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Debt (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
Debt (Narrative) (Details) - USD ($) $ in Thousands	Nov. 30, 2017	Nov. 30, 2016	Feb. 28, 2017
Debt Instrument [Line Items]
Non-recourse notes payable	$ 11,487,028		$ 10,742,425
Capitalized interest	5,800	$ 8,400
Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	1,200,000
Unused capacity	954,400
Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument Face Amount	300,000
Outstanding Balance	300,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Face Amount	500,000
Outstanding Balance	$ 500,000
Finance and capital lease obligation \| Minimum
Debt Instrument [Line Items]
Initial lease terms, in years	15 years
Finance and capital lease obligation \| Maximum
Debt Instrument [Line Items]
Initial lease terms, in years	20 years
Asset-backed term funding transactions
Debt Instrument [Line Items]
Non-recourse notes payable	$ 9,610,000
Debt maturity, end	May 15, 2024
Warehouse facilities
Debt Instrument [Line Items]
Non-recourse notes payable	$ 1,880,000
Warehouse Facilities Maximum Borrowing Capacity	2,940,000
Remaining borrowing capacity	1,060,000
Warehouse Facility Three [Member]
Debt Instrument [Line Items]
Warehouse Facilities Maximum Borrowing Capacity	140,000
Warehouse Facility Two
Debt Instrument [Line Items]
Warehouse Facilities Maximum Borrowing Capacity	1,500,000
Warehouse Facility One
Debt Instrument [Line Items]
Warehouse Facilities Maximum Borrowing Capacity	$ 1,300,000