v2.4.0.6

Auto Loan Receivables (Past Due Receivables) (Details) (USD $) In Millions, unless otherwise specified					9 Months Ended		12 Months Ended		9 Months Ended		12 Months Ended		9 Months Ended		12 Months Ended		9 Months Ended		12 Months Ended		9 Months Ended		12 Months Ended
	Nov. 30, 2011	Feb. 28, 2011	Nov. 30, 2010	Feb. 28, 2010	Nov. 30, 2011 31-60 Days Past Due [Member]		Feb. 28, 2011 31-60 Days Past Due [Member]		Nov. 30, 2011 61-90 Days Past Due [Member]		Feb. 28, 2011 61-90 Days Past Due [Member]		Nov. 30, 2011 Greater Than 90 Days Past Due [Member]		Feb. 28, 2011 Greater Than 90 Days Past Due [Member]		Nov. 30, 2011 Total Past Due [Member]		Feb. 28, 2011 Total Past Due [Member]		Nov. 30, 2011 Managed Receivables [Member]		Feb. 28, 2011 Managed Receivables [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total ending managed receivables	$ 4,823.8	$ 4,334.6	$ 4,288.1	$ 4,112.7
31-60 days past due	103.3	86.6
61-90 days past due	28.4	24.2
Greater than 90 days past due	10.6	10.5
Total past due	$ 142.3	$ 121.3
Percentage of total ending managed receivables					2.20%	[1]	2.00%	[1]	0.60%	[1]	0.60%	[1]	0.20%	[1]	0.20%	[1]	3.00%	[1]	2.80%	[1]	100.00%	[1]	100.00%	[1]
[1] Percent of total ending managed receivables.

X

- Definition

Item as percent of total ending managed receivables

+ References

No definition available.

+ Details

Name:	kmx_ItemAsPercentOfTotalEndingManagedReceivables
Namespace Prefix:	kmx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of the recorded investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, accounts receivable (with terms exceeding one year), notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Receivable

-URI http://asc.fasb.org/extlink&oid=6953735

+ Details

Name:	us-gaap_FinancingReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Financing receivables that are less than 60 days past due but more than 29 days past due.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953401-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Financing receivables that are less than 90 days past due but more than 59 days past due.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953401-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Financing receivables that are equal to or greater than 90 days past due.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953401-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953401-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration