CarMax Auto Finance (Components Of CarMax Auto Finance Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Auto Finance Income [Line Items]
Interest and fee income	$ 278,900	$ 247,800	$ 820,800	$ 722,300
Interest expense	(90,400)	(75,300)	(268,400)	(208,200)
Total interest margin	188,500	172,500	552,400	514,100
Provision for loan losses	(49,000)	(40,800)	(132,700)	(111,700)
Total interest margin after provision for loan losses	139,500	131,700	419,700	402,400
Total other expense	0	(100)	0	(400)
Payroll and fringe benefit expense	(10,800)	(9,400)	(31,300)	(28,600)
Other direct expenses	(14,700)	(12,500)	(44,300)	(38,400)
Total direct expenses	(25,500)	(21,900)	(75,600)	(67,000)
CarMax Auto Finance income	114,033	109,725	344,123	334,985
Total average managed receivables	$ 13,239,200	$ 12,321,000	$ 12,986,200	$ 12,054,600
Interest and fee income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	8.40%	8.00%	8.40%	8.00%
Interest expense, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(2.70%)	(2.40%)	(2.80%)	(2.30%)
Total interest margin, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	5.70%	5.60%	5.70%	5.70%
Provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(1.50%)	(1.30%)	(1.40%)	(1.20%)
Total interest margin after provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	4.20%	4.30%	4.30%	4.50%
Total other expense, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	0.00%	0.00%	0.00%	0.00%
Payroll and fringe benefit expense, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(0.30%)	(0.30%)	(0.30%)	(0.30%)
Other direct expenses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(0.40%)	(0.40%)	(0.50%)	(0.40%)
Total direct expenses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(0.80%)	(0.70%)	(0.80%)	(0.70%)
CarMax Auto Finance income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	3.40%	3.60%	3.50%	3.70%