CarMax Auto Finance (Components Of CarMax Auto Finance Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 29, 2020	Feb. 28, 2019	Feb. 28, 2018
Auto Finance Income [Line Items]
Interest and fee income									$ 1,104,100	$ 972,900	$ 856,600
Interest expense									(358,100)	(289,300)	(215,000)
Total interest margin									746,000	683,600	641,600
Provision for loan losses									(185,700)	(153,800)	(137,600)
Total interest margin after provision for loan losses									560,300	529,800	504,000
Total other (expense) income									0	(400)	400
Payroll and fringe benefit expense									(42,300)	(38,300)	(35,400)
Other direct expenses									(62,000)	(52,400)	(47,800)
Total direct expenses									(104,300)	(90,700)	(83,200)
CarMax Auto Finance income	$ 111,907	$ 114,033	$ 114,131	$ 115,959	$ 103,705	$ 109,725	$ 109,667	$ 115,593	456,030	438,690	421,182
Total average managed receivables									$ 13,105,100	$ 12,150,200	$ 11,210,800
Interest And Fee Income, Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									8.40%	8.00%	7.60%
Interest Expense, Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									(2.70%)	(2.40%)	(1.90%)
Total Interest Margin, Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									5.70%	5.60%	5.70%
Provision For Loan Losses, Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									(1.40%)	(1.30%)	(1.20%)
Total Interest Margin After Provision For Loan Losses, Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									4.30%	4.40%	4.50%
Other Income (Expense), Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									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%)
Other Direct Expenses, Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									(0.50%)	(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%)
CAF Income, Percent
Auto Finance Income [Line Items]
Item as percent of total average managed receivables									3.50%	3.60%	3.80%