Document And Entity Information - USD ($)	12 Months Ended
	Feb. 28, 2022	Mar. 31, 2022	Aug. 31, 2021
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Feb. 28, 2022
Document Transition Report	false
Entity File Number	001-31420
Entity Registrant Name	CARMAX, INC.
Entity Central Index Key	0001170010
Current Fiscal Year End Date	--02-28
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	VA
Entity Tax Identification Number	54-1821055
Entity Address, Address Line One	12800 Tuckahoe Creek Parkway
Entity Address, City or Town	Richmond,
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	23238
City Area Code	804
Local Phone Number	747-0422
Title of 12(b) Security	Common Stock
Trading Symbol	KMX
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
ICFR Auditor Attestation Flag	true
Entity Public Float			$ 20,342,890,361
Entity Common Stock, Shares Outstanding		160,537,858
Auditor Name	KPMG LLP
Auditor Location	Richmond, VA
Auditor Firm ID	185