Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenues		$ 6,485.7	$ 6,398.7
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues		5,573.6	5,570.3
Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	[1]	912.1	828.4
New vehicle
Disaggregation of Revenue [Line Items]
Revenues		2,979.3	2,931.9
Used vehicle
Disaggregation of Revenue [Line Items]
Revenues		1,996.1	2,032.6
Parts and service
Disaggregation of Revenue [Line Items]
Revenues		1,172.4	1,089.8
Finance and insurance, net
Disaggregation of Revenue [Line Items]
Revenues		334.7	332.4
Other
Disaggregation of Revenue [Line Items]
Revenues		3.2	12.0
Domestic
Disaggregation of Revenue [Line Items]
Revenues		1,756.7	1,831.1
Domestic | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues		1,538.3	1,629.3
Domestic | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	[1]	218.4	201.8
Domestic | New vehicle
Disaggregation of Revenue [Line Items]
Revenues		814.4	828.0
Domestic | Used vehicle
Disaggregation of Revenue [Line Items]
Revenues		543.0	612.3
Domestic | Parts and service
Disaggregation of Revenue [Line Items]
Revenues		302.1	287.6
Domestic | Finance and insurance, net
Disaggregation of Revenue [Line Items]
Revenues		97.0	102.3
Domestic | Other
Disaggregation of Revenue [Line Items]
Revenues		0.2	0.9
Import
Disaggregation of Revenue [Line Items]
Revenues		1,979.5	1,789.3
Import | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues		1,748.3	1,586.9
Import | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	[1]	231.2	202.4
Import | New vehicle
Disaggregation of Revenue [Line Items]
Revenues		1,006.8	856.4
Import | Used vehicle
Disaggregation of Revenue [Line Items]
Revenues		557.2	542.1
Import | Parts and service
Disaggregation of Revenue [Line Items]
Revenues		294.7	268.4
Import | Finance and insurance, net
Disaggregation of Revenue [Line Items]
Revenues		119.2	112.4
Import | Other
Disaggregation of Revenue [Line Items]
Revenues		1.6	10.0
Premium Luxury
Disaggregation of Revenue [Line Items]
Revenues		2,414.9	2,484.9
Premium Luxury | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues		2,057.9	2,159.3
Premium Luxury | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	[1]	357.0	325.6
Premium Luxury | New vehicle
Disaggregation of Revenue [Line Items]
Revenues		1,158.1	1,247.5
Premium Luxury | Used vehicle
Disaggregation of Revenue [Line Items]
Revenues		736.2	745.8
Premium Luxury | Parts and service
Disaggregation of Revenue [Line Items]
Revenues		417.2	386.2
Premium Luxury | Finance and insurance, net
Disaggregation of Revenue [Line Items]
Revenues		103.3	105.0
Premium Luxury | Other
Disaggregation of Revenue [Line Items]
Revenues		0.1	0.4
Corporate and other
Disaggregation of Revenue [Line Items]
Revenues	[2]	334.6	293.4
Corporate and other | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	[2]	229.1	194.8
Corporate and other | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	[1],[2]	105.5	98.6
Corporate and other | New vehicle
Disaggregation of Revenue [Line Items]
Revenues	[2]	0.0	0.0
Corporate and other | Used vehicle
Disaggregation of Revenue [Line Items]
Revenues	[2]	159.7	132.4
Corporate and other | Parts and service
Disaggregation of Revenue [Line Items]
Revenues	[2]	158.4	147.6
Corporate and other | Finance and insurance, net
Disaggregation of Revenue [Line Items]
Revenues	[2]	15.2	12.7
Corporate and other | Other
Disaggregation of Revenue [Line Items]
Revenues	[2]	$ 1.3	$ 0.7

[1] (2) Represents revenue recognized during the period for automotive repair and maintenance services.

[2] (1) “Corporate and other” is comprised of our non-franchised businesses, including AutoNation USA used vehicle stores, collision centers, parts distribution centers, auction operations, and AutoNation Mobile Service.