CarMax Auto Finance (Components Of CarMax Auto Finance Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016
Auto Finance Income [Line Items]
Interest and fee income	$ 217,100	$ 192,700	$ 637,400	$ 567,000
Interest expense	(55,400)	(44,100)	(156,600)	(125,300)
Total interest margin	161,700	148,600	480,800	441,700
Provision for loan losses	(37,500)	(41,900)	(99,000)	(104,200)
Total interest margin after provision for loan losses	124,200	106,700	381,800	337,500
Payroll and fringe benefit expense	(8,900)	(7,500)	(26,200)	(22,900)
Other direct expenses	(12,500)	(9,800)	(35,500)	(28,500)
Total direct expenses	(21,400)	(17,300)	(61,700)	(51,400)
CarMax Auto Finance income	102,810	89,359	320,109	286,086
Total average managed receivables	$ 11,365,600	$ 10,297,800	$ 11,102,400	$ 10,030,900
Interest and fee income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	7.60%	7.50%	7.70%	7.50%
Interest expense, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(2.00%)	(1.70%)	(1.90%)	(1.70%)
Total interest margin, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	5.70%	5.80%	5.80%	5.90%
Provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(1.30%)	(1.60%)	(1.20%)	(1.40%)
Total interest margin after provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	4.40%	4.10%	4.60%	4.50%
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	(0.80%)	(0.70%)	(0.70%)	(0.70%)
CarMax Auto Finance income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	3.60%	3.50%	3.90%	3.80%