Financial Instruments and Fair Value Measurements - Impact of Interest Rate Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Amount of unrealized income (loss), net of tax, recognized in other comprehensive (loss) income	$ (1.8)	$ (5.6)	$ (40.4)	$ (19.2)
Floorplan interest expense, net
Derivative [Line Items]
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations			(5.3)	0.4
Other interest expense, net
Derivative [Line Items]
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations			$ (1.8)	$ 0.3