Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2021	Aug. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 7,988.4	$ 5,372.2	$ 15,686.0	$ 8,600.9
Used vehicle sales
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6,104.4	4,389.2	12,261.7	7,175.4
Wholesale vehicle sales
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,701.6	819.1	3,075.9	1,161.9
Extended protection plan revenues
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	113.0	119.4	247.3	192.8
Third-party finance fees, net
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2.8	(15.4)	(1.8)	(26.2)
Advertising & subscription revenues [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	34.5	0.0	34.5	0.0
Service revenues
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	21.0	26.5	43.2	46.0
Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	11.1	33.4	25.1	51.0
Total other sales and revenues
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 182.4	$ 163.9	$ 348.3	$ 263.6