Accounts Receivable (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	$ 567.4	$ 573.7
Less: Allowance for doubtful accounts	(7.3)	(7.2)
Less: Long-term portion of accounts receivable, net	(55.1)	(37.1)
Total accounts receivable, net	505.0	529.4
Contracts in transit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	269.7	294.0
Trade receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	52.8	54.3
Vehicle receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	50.9	51.6
Manufacturer receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	112.4	105.5
Auto loan receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	62.2	61.5
Other receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable gross	$ 19.4	$ 6.8