CarMax Auto Finance (Components Of CarMax Auto Finance Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2018	Aug. 31, 2017
Auto Finance Income [Line Items]
Interest and fee income	$ 242,200	$ 213,600	$ 474,500	$ 420,300
Interest expense	(69,100)	(52,200)	(132,900)	(101,200)
Total interest margin	173,100	161,400	341,600	319,100
Provision for loan losses	(40,000)	(32,900)	(70,900)	(61,500)
Total interest margin after provision for loan losses	133,100	128,500	270,700	257,600
Total other expense	(300)	0	(300)	0
Payroll and fringe benefit expense	(9,600)	(8,800)	(19,200)	(17,300)
Other direct expenses	(13,500)	(11,800)	(25,900)	(23,000)
Total direct expenses	(23,100)	(20,600)	(45,100)	(40,300)
CarMax Auto Finance income	109,667	107,936	225,260	217,299
Total average managed receivables	$ 12,067,500	$ 11,112,000	$ 11,921,400	$ 10,970,800
Interest and fee income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	8.00%	7.70%	8.00%	7.70%
Interest expense, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(2.30%)	(1.90%)	(2.20%)	(1.80%)
Total interest margin, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	5.70%	5.80%	5.70%	5.80%
Provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(1.30%)	(1.20%)	(1.20%)	(1.10%)
Total interest margin after provision for loan losses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	4.40%	4.60%	4.50%	4.70%
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%)	(0.40%)	(0.40%)
Total direct expenses, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	(0.80%)	(0.70%)	(0.80%)	(0.70%)
CarMax Auto Finance income, percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables	3.60%	3.90%	3.80%	4.00%