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Inventory and Vehicle Floorplan Payable (Components of Inventory) (Details) - USD ($) $ in Millions | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Inventory [Line Items] |  |
Inventory | $ 3,612.0 | $ 2,899.0
New Vehicle [Member] |  |
Inventory [Line Items] |  |
Inventory | 2,888.1 | 2,294.3
Used Vehicle [Member] |  |
Inventory [Line Items] |  |
Inventory | 539.7 | 437.6
Parts and Service [Member] |  |
Inventory [Line Items] |  |
Inventory | $ 184.2 | $ 167.1

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- Definition Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -SubTopic 10 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=51655945&loc=d3e3927-108312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 + Details
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