Stock and Stock-Based Incentive Plans (Composition of Share-Based Compensation Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Aug. 31, 2026	Aug. 31, 2025	Aug. 31, 2026	Aug. 31, 2025
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	$ 32,923	$ 24,813	$ 75,477	$ 72,472
Income Statement Location [Axis]: us-gaap:CostOfRevenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	1,955	1,222	3,427	1,869
Income Statement Location [Axis]: us-gaap:SellingGeneralAndAdministrativeExpense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	29,058	22,445	68,761	68,047
Income Statement Location [Axis]: kmx:NetIncomeLossFromFinancing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	$ 1,910	$ 1,146	$ 3,289	$ 2,556