CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Repayment of sellers' floor plan notes payable dealership acquisitions	$ 43.0	$ 0.0	$ 138.5
3.50% senior subordinated notes due 2025
Interest rate (as a percent)	3.50%
3.75% senior subordinated notes due 2029
Interest rate (as a percent)	3.75%	3.75%
3.75% senior subordinated notes due 2020
Interest rate (as a percent)	3.75%
5.375% senior subordinated notes due 2024
Interest rate (as a percent)	5.375%
5.50% senior subordinated notes due 2026 redeemed June 24, 2021
Interest rate (as a percent)	5.50%
5.75% senior subordinated notes due 2022
Interest rate (as a percent)	5.75%