Goodwill and Franchise Value - Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2008
Goodwill [Roll Forward]
Balance			$ 593.0	$ 454.6
Additions through acquisitions			395.5	144.9
Reductions through divestitures			(11.2)	(3.0)
Reductions from impairments	$ (3.5)	$ (1.7)		(3.5)
Balance		454.6	977.3	593.0
Accumulated impairment losses					$ 299.3
Additions through acquisitions			395.5	144.9
Domestic
Goodwill [Roll Forward]
Balance			204.5	171.8
Additions through acquisitions			101.0	33.3
Reductions through divestitures			(1.5)	(0.1)
Reductions from impairments				(0.5)
Balance		171.8	304.0	204.5
Additions through acquisitions			101.0	33.3
Import
Goodwill [Roll Forward]
Balance			287.9	197.3
Additions through acquisitions			188.7	94.3
Reductions through divestitures			(8.4)	(0.7)
Reductions from impairments				(3.0)
Balance		197.3	468.2	287.9
Additions through acquisitions			188.7	94.3
Luxury
Goodwill [Roll Forward]
Balance			100.6	85.5
Additions through acquisitions			105.8	17.3
Reductions through divestitures			(1.3)	(2.2)
Reductions from impairments				0.0
Balance		$ 85.5	205.1	100.6
Additions through acquisitions			$ 105.8	$ 17.3