Exit or Disposal Cost Obligations (Details) - AutoNation Collision Parts Closure $ in Millions	3 Months Ended
	Sep. 30, 2020 USD ($)
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	$ 43.7
Costs Incurred	36.5
Cost of Sales | Parts and Service [Member] | Inventory Valuation Adjustment
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	20.6
Costs Incurred	20.6
Other Operating Income (Expense) | Contract Termination
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	7.3
Costs Incurred	7.3
Other Operating Income (Expense) | Asset Impairment Charges
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	3.0
Costs Incurred	2.8
Selling, General and Administrative Expenses | Other Restructuring
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	4.5
Costs Incurred	0.0
Selling, General and Administrative Expenses | Accelerated Amortization
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	3.2
Costs Incurred	2.1
Selling, General and Administrative Expenses | Employee Severance
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	1.2
Costs Incurred	0.8
Depreciation and amortization | Accelerated Depreciation
Exit or Disposal Cost Obligations [Line Items]
Total Costs Expected to be Incurred	3.9
Costs Incurred	$ 2.9