This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Acquisitions (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended
Acquisitions (Narrative) (Details) $ in Millions	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 01, 2018 store	Feb. 26, 2018 store
Business Acquisition [Line Items]
Acquisition expense recognized \| $	$ 1.5	$ 3.3	$ 1.6	$ 4.2
Day Auto Group
Business Acquisition [Line Items]
Number of stores acquired						7
Prestige Auto Group
Business Acquisition [Line Items]
Number of stores acquired					6