Receivables and Contract Assets, Net - Financial Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contracts-in-transit	$ 67.0	$ 169.9
Vehicle receivables	48.7	84.3
Total contracts-in-transit and vehicle receivables	115.8	254.1
Less: allowance for doubtful accounts	0.3	0.3
Total contracts-in-transit and vehicle receivables, net	115.5	253.8
Accounts and notes receivable
Accounts and notes receivable	180.5	227.9
Less: allowance for doubtful accounts	3.4	2.8
Accounts and notes receivable, net	177.1	225.1
Adjustment to credit losses as result of COVID-19	0.4
Total contract assets, net	22.7	21.6
Manufacturer receivables
Accounts and notes receivable
Accounts and notes receivable	97.5	124.0
Parts and service receivables
Accounts and notes receivable
Accounts and notes receivable	51.2	57.0
F&I receivables
Accounts and notes receivable
Accounts and notes receivable	19.0	28.3
Other
Accounts and notes receivable
Accounts and notes receivable	$ 12.8	$ 18.6