Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) segments	Sep. 30, 2019 USD ($) segments
Segment Reporting Information [Line Items]
Number of reportable segments | segments			3	3
Revenues	$ 5,404.9	$ 5,461.2	$ 14,604.9	$ 15,786.8
Segment Income	379.3	246.2	839.1	701.9
AN Reportable Segment, Domestic [Member]
Segment Reporting Information [Line Items]
Revenues	1,734.5	1,728.6	4,704.0	5,004.7
Segment Income	111.9	70.3	248.1	192.4
AN Reportable Segment, Import [Member]
Segment Reporting Information [Line Items]
Revenues	1,621.5	1,722.5	4,308.9	4,845.9
Segment Income	123.5	86.9	277.7	240.9
AN Reportable Segment, Premium Luxury [Member]
Segment Reporting Information [Line Items]
Revenues	1,870.0	1,820.5	5,051.6	5,375.5
Segment Income	$ 143.9	$ 89.0	$ 313.3	$ 268.6