Selected Quarterly Financial Data (Schedule Of Selected Quarterly Financial Data) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Net sales and operating revenues	$ 4,962,490	$ 4,790,028	$ 5,201,151	$ 5,366,318	$ 4,318,602	$ 4,295,871	$ 4,766,035	$ 4,792,592	$ 20,319,987	$ 18,173,100	$ 17,120,209
Gross profit	672,857	613,647	693,453	742,383	599,378	569,237	650,636	661,340	2,722,340	2,480,591	2,328,859
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
Selling, general and administrative expenses	484,728	484,848	480,831	489,660	428,967	409,520	453,554	438,234	1,940,067	1,730,275	1,617,051
Net earnings	$ 214,934	$ 173,156	$ 233,599	$ 266,744	$ 192,556	$ 190,311	$ 220,890	$ 238,656	$ 888,433	$ 842,413	$ 664,112
Basic net earnings per share (in dollars per share)	$ 1.32	$ 1.05	$ 1.41	$ 1.60	$ 1.14	$ 1.09	$ 1.25	$ 1.34	$ 5.39	$ 4.83	$ 3.64
Diluted net earnings per share (in dollars per share)	$ 1.30	$ 1.04	$ 1.40	$ 1.59	$ 1.13	$ 1.09	$ 1.24	$ 1.33	$ 5.33	$ 4.79	$ 3.60