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Interim Financial Information (Details Textual) $ in Thousands |  | 3 Months Ended |  |
--- | --- | --- | --- | ---
Jan. 01, 2018 USD ($) | Mar. 31, 2018 USD ($) dealerships town states | Mar. 31, 2017 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Business And Organization [Line Items] |  |  |  |  |
Value of used vehicle inventory financed |  | 85.00% |  |  |
Parts And Service Sales |  | $ 349,515 | $ 319,698 |  |
Accounts, Notes, Loans and Financing Receivable, Net, Current | $ 208,917 | 200,159 |  | $ 188,611 |
Inventory, Net | (1,759,633) | (1,804,176) |  | (1,763,293) |
Accounts Payable, Current | 414,737 | 491,841 |  | 412,981 |
Deferred Tax Liabilities, Net, Noncurrent | 127,897 | 134,800 |  | 124,404 |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | 11,397 |  |  |  |
Retained Earnings (Accumulated Deficit) | 1,257,720 | 1,288,052 |  | 1,246,323 |
Cash and Cash Equivalents, at Carrying Value |  | $ 33,090 |  | 28,787 | $ 24,246
Number of International Regions |  | 2 |  |  |
Number of Reportable Segments |  | 3 |  |  |
Restricted Cash and Cash Equivalents |  | $ 34,559 | 34,680 | 29,631 | $ 24,246
Financial Services Revenue |  | 112,322 | 96,834 |  |
Parts And Service Sales Cost Of Sales |  | 162,651 | 147,342 |  |
Selling, General and Administrative Expense |  | (324,347) | (289,779) |  |
Income Tax Expense (Benefit) |  | 10,353 | 17,257 |  |
Net Income (Loss) Attributable to Parent |  | 35,814 | 33,939 |  |
Accrued Liabilities, Current |  | (194,248) |  | (177,070) |
Interest Paid |  | 20,300 | 17,600 |  |
Proceeds from Income Tax Refunds |  | 400 | 300 |  |
BRAZIL |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Parts And Service Sales |  | $ 11,860 | 11,758 |  |
Number of States in which Entity Operates | states |  | 4 |  |  |
Number of Dealerships | dealerships |  | 16 |  |  |
Financial Services Revenue |  | $ 1,872 | 1,987 |  |
Income Tax Expense (Benefit) |  | 134 | 40 |  |
Net Income (Loss) Attributable to Parent |  | (214) | 169 |  |
UNITED STATES |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Parts And Service Sales |  | $ 284,514 | 271,159 |  |
Number of States in which Entity Operates | states |  | 15 |  |  |
Number of Dealerships | dealerships |  | 117 |  |  |
Financial Services Revenue |  | $ 96,187 | 85,819 |  |
Income Tax Expense (Benefit) |  | 9,357 | 16,347 |  |
Net Income (Loss) Attributable to Parent |  | 31,153 | 29,259 |  |
UNITED KINGDOM |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Parts And Service Sales |  | $ 53,141 | 36,781 |  |
Number of Towns in which Entity Operates | town |  | 32 |  |  |
Number of Dealerships | dealerships |  | 47 |  |  |
Financial Services Revenue |  | $ 14,263 | 9,028 |  |
Income Tax Expense (Benefit) |  | 862 | 870 |  |
Net Income (Loss) Attributable to Parent |  | 4,875 | 4,511 |  |
Investments [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Investments, Fair Value Disclosure |  | 1,469 | $ 844 | $ 844 |
Accounting Standards Update 2014-09 [Member] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Parts And Service Sales |  | 350,992 |  |  |
Accounts, Notes, Loans and Financing Receivable, Net, Current |  | 181,131 |  |  |
Inventory, Net |  | (1,807,371) |  |  |
Accounts Payable, Current |  | 490,281 |  |  |
Deferred Tax Liabilities, Net, Noncurrent |  | 131,459 |  |  |
Retained Earnings (Accumulated Deficit) |  | 1,277,120 |  |  |
Financial Services Revenue |  | 112,122 |  |  |
Parts And Service Sales Cost Of Sales |  | 163,116 |  |  |
Selling, General and Administrative Expense |  | (324,543) |  |  |
Income Tax Expense (Benefit) |  | 10,504 |  |  |
Net Income (Loss) Attributable to Parent |  | 36,279 |  |  |
Accounting Standards Update 2014-09 [Member] | PartsandServiceSales606 [Domain] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption | 4,800 |  |  |  |
Accounting Standards Update 2014-09 [Member] | FinanceandInsuranceSales606 [Domain] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption | 6,600 |  |  |  |
Accounts Receivable [Member] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | 20,306 |  |  |  |
Inventories [Member] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | (3,660) |  |  |  |
Accounts Payable [Member] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | 1,756 |  |  |  |
Other Noncurrent Liabilities [Member] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | $ 3,493 |  |  |  |
Accounting Standards Update 2014-09 [Member] |  |  |  |  |
Business And Organization [Line Items] |  |  |  |  |
Parts And Service Sales |  | (1,477) |  |  |
Accounts, Notes, Loans and Financing Receivable, Net, Current |  | 19,028 |  |  |
Inventory, Net |  | (3,195) |  |  |
Accounts Payable, Current |  | 1,560 |  |  |
Deferred Tax Liabilities, Net, Noncurrent |  | 3,341 |  |  |
Retained Earnings (Accumulated Deficit) |  | 10,932 |  |  |
Financial Services Revenue |  | 200 |  |  |
Parts And Service Sales Cost Of Sales |  | (465) |  |  |
Selling, General and Administrative Expense |  | (196) |  |  |
Income Tax Expense (Benefit) |  | (151) |  |  |
Net Income (Loss) Attributable to Parent |  | $ (465) |  |  |

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