v2.4.0.6

Auto Loan Receivables (Allowance For Loan Losses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2012 Allowance For Loan Losses [Member]		Aug. 31, 2012 Allowance For Loan Losses [Member]		Feb. 29, 2012 Allowance For Loan Losses [Member]		Nov. 30, 2011 Allowance For Loan Losses [Member]		Aug. 31, 2011 Allowance For Loan Losses [Member]		Feb. 28, 2011 Allowance For Loan Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance as of beginning of period	$ 49.5	$ 36.2	$ 43.3	$ 38.9
Charge-offs	(28.2)	(24.6)	(73.1)	(67.1)
Recoveries	14.9	14.7	43.9	44.7
Provision for loan losses	18.1	15.1	40.2	24.9
Balance as of end of period	$ 54.3	$ 41.4	$ 54.3	$ 41.4
Item as percent of total ending managed receivables					1.00%	[1]	0.90%	[1]	0.90%	[1]	0.90%	[1]	0.80%	[1]	0.90%	[1]
[1] (1) Percent of total ending managed receivables as of the corresponding reporting date.

X

- Definition

Item as percent of total ending managed receivables

+ References

No definition available.

+ Details

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Namespace Prefix:	kmx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524

+ Details

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Period Type:	instant

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- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of recovery of financing receivables doubtful of collection that were previously charged off.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(4)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524

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Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of direct write-downs of financing receivables charged against the allowance.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524

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X

- Definition

The sum of the periodic provision charged to earnings, based on an assessment of uncollectibility from the counterparty on account of loan, lease or other credit losses, to reduce these accounts to the amount that approximates their net realizable value.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 9



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953423-111524



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Paragraph 168, 169, 170

-IssueDate 2006-05-01

-Chapter 5

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585



Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.11)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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