This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

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

Acquisitions - Pro Forma Information (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016
Assets Or Stock Of Multiple Dealership Locations Acquired
Acquisitions
Revenue		$ 117.7	$ 48.0
Pre-tax income (loss)		$ 7.8	$ 1.3
Gander Mountain and Overton's
Acquisitions
Revenue	$ 8.4
Pre-tax income (loss)	$ (1.6)