Acquisitions - General Information (Details) $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($) location
Acquisitions
Real properties purchased from parties related to the sellers of the dealership businesses	$ 0.7
Assets or stock of multiple dealership locations acquired during the first quarters of 2015 and 2016
Acquisitions
Number of locations acquired \| location	3
Payments to acquire assets	$ 38.6
Borrowing to purchase of business	$ 8.4

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

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