Stock and Stock-Based Incentive Plans Stock And Stock-Based Incentive Plans (Composition of Share-Based Compensation Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Nov. 30, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	$ 36,784	$ 11,677	$ 110,921	$ 75,632
Cost of sales
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	1,896	11	5,719	3,202
Carmax Auto Finance Income
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	1,560	938	4,749	3,750
Selling, general and administrative expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense, before income taxes	$ 33,328	$ 10,728	$ 100,453	$ 68,680