Financial Instruments and Fair Value Measurements - Impact of Interest Rate Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Derivative [Line Items]
Amount of unrealized income (loss), net of tax, recognized in other comprehensive (loss) income	$ (31.6)	$ (4.2)	$ (4.2)
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations	(0.5)	$ 0.3
Floorplan interest expense, net
Derivative [Line Items]
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations	(0.6)		0.3
Other interest expense, net
Derivative [Line Items]
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations	$ (0.1)		$ 0.1