CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unrealized gain (loss) on interest rate swaps, tax:
Unrealized loss arising during the period, tax provision (benefit)	$ 1.3	$ 0.0	$ 0.0
Reclassification adjustment for loss included in floor plan interest expense, tax benefit	$ 0.2	$ (0.0)	$ (0.0)

Amount of tax expense (benefit) for reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e640-108580

Name:	us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration