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Description of Business and Summary of Significant Accounting Policies (Goodwill and Other Intangible Assets) (Details) - USD ($) | 4 Months Ended | 12 Months Ended
--- | --- | ---
Apr. 30, 2015 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Goodwill and Intangible Assets [Line Items] |  |  |  |
Franchise agreements, minimal contractual terms (in years) |  | 1 year |  |
Franchise rights impairment |  | $ 15,400,000 | $ 0 | $ 0
Goodwill [Member] |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |
Date of annual goodwill and indefinite lived intangible assets impairment test |  | April 30 | April 30 |
Franchise Rights [Member] |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |
Date of annual goodwill and indefinite lived intangible assets impairment test |  | April 30 | April 30 |
Maximum [Member] |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |
Other intangibles, useful life |  | 30 years |  |
Minimum [Member] |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |
Other intangibles, useful life |  | 3 years |  |
Nonrecurring [Member] |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |
Goodwill impairment |  | $ 0 | $ 0 |
Nonrecurring [Member] | Franchise Rights [Member] |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |
Franchise rights impairment | $ 0 | 15,400,000.0 | $ 0 |
Nonrecurring [Member] | Franchise Rights [Member] | Volkswagen [Member] |  |  |  |
Goodwill and Intangible Assets [Line Items] |  |  |  |
Franchise rights impairment |  | 15,400,000 |  |
Franchise rights impairment, after tax |  | $ 9,600,000 |  |

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- Definition The minimum contractual term of the Company's various franchise agreements with vehicle manufacturers. + References No definition available. + Details
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- Definition The amount of impairment loss recognized in the period, resulting from the write-down of the carrying amount of an indefinite-lived intangible asset, other than goodwill, to fair value, net of taxes. + References No definition available. + Details
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- Definition Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 + Details
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