Accumulated Other Comprehensive Loss (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Feb. 28, 2014	Feb. 28, 2013
Accumulated Other Comprehensive Loss [Abstract]
Deferred tax	$ 27.7	$ 35.9

The balance of deferred taxes on items remaining in accumulated other comprehensive income loss

No definition available.

Name:	kmx_AccumulatedOtherComprehensiveIncomeLossDeferredTaxes
Namespace Prefix:	kmx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration