CarMax Auto Finance (Components Of CarMax Auto Finance Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2016	Nov. 30, 2015
Auto Finance Income [Line Items]
Interest and fee income	$ 192,700	$ 172,300	$ 567,000	$ 507,000
Interest expense	(44,100)	(33,000)	(125,300)	(91,900)
Total interest margin	148,600	139,300	441,700	415,100
Provision for loan losses	(41,900)	(30,900)	(104,200)	(70,200)
Total interest margin after provision for loan losses	106,700	108,400	337,500	344,900
Other Nonoperating Expense	0	(300)	0	(400)
Payroll and fringe benefit expense	(7,500)	(7,100)	(22,900)	(21,000)
Other direct expenses	(9,800)	(8,700)	(28,500)	(23,800)
Total direct expenses	(17,300)	(15,800)	(51,400)	(44,800)
CarMax Auto Finance income	89,359	92,316	286,086	299,703
Total average managed receivables	$ 10,297,800	$ 9,261,400	$ 10,030,900	$ 8,973,300
Interest and fee income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	7.50%	7.40%	7.50%	7.50%
Interest expense, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(1.70%)	(1.40%)	(1.70%)	(1.40%)
Total interest margin, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	5.80%	6.00%	5.90%	6.20%
Provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(1.60%)	(1.30%)	(1.40%)	(1.00%)
Total interest margin after provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	4.10%	4.70%	4.50%	5.10%
Other Nonoperating Expense [Member]
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%)	(0.40%)	(0.40%)
Total direct expenses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(0.70%)	(0.70%)	(0.70%)	(0.70%)
CarMax Auto Finance income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	3.50%	4.00%	3.80%	4.50%