Fair Value Measurements Fair Value Measurements (Policies)	3 Months Ended
Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Assets Acquired and Liabilities Assumed [Policy Text Block]	ASC 820 defines fair value as the price that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date; requires disclosure of the extent to which fair value is used to measure financial and non-financial assets and liabilities, the inputs utilized in calculating valuation measurements, and the effect of the measurement of significant unobservable inputs on earnings, or changes in net assets, as of the measurement date; and establishes a three-level valuation hierarchy based upon the transparency of inputs utilized in the measurement and valuation of financial assets or liabilities as of the measurement date: •Level 1 — unadjusted, quoted prices for identical assets or liabilities in active markets; •Level 2 — quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs other than quoted market prices that are observable or that can be corroborated by observable market data by correlation; and •Level 3 — unobservable inputs based upon the reporting entity’s internally developed assumptions that market participants would use in pricing the asset or liability. The Company’s financial instruments consist primarily of cash and cash equivalents, contracts-in-transit and vehicle receivables, accounts and notes receivable, investments in debt and equity securities, accounts payable, credit facilities, long-term debt and interest rate derivative instruments. The fair values of cash and cash equivalents, contracts-in-transit and vehicle receivables, accounts and notes receivable, accounts payable, and credit facilities approximate their carrying values due to the short-term nature of these instruments and/or the existence of variable interest rates. The Company evaluated its assets and liabilities for those that met the criteria of the disclosure requirements and fair value framework of ASC 820 and identified demand obligations, interest rate derivative instruments, and investment balances in certain financial institutions as having met such criteria. See Note 10, "Long-Term Debt" for details regarding the fair value of the Company's long-term debt. The Company periodically invests in unsecured, corporate demand obligations with manufacturer-affiliated finance companies, which bear interest at a variable rate and are redeemable on demand by the Company. Therefore, the Company has classified these demand obligations as cash and cash equivalents in the accompanying Consolidated Balance Sheets. The Company determined that the valuation measurement inputs of these instruments include inputs other than quoted market prices, that are observable or that can be corroborated by observable data by correlation. Accordingly, the Company has classified these instruments within Level 2 of the hierarchy framework. In addition, the Company maintains an investment balance with certain of the financial institutions in Brazil that provide credit facilities for the financing of new, used and rental vehicle inventories. The investment balances bear interest at a variable rate and are redeemable by the Company in the future under certain conditions. The Company has classified these investment balances as restricted cash within other assets in the accompanying Consolidated Balance Sheets. The Company determined that the valuation measurement inputs of these instruments include inputs other than quoted market prices, that are observable or that can be corroborated by observable data by correlation. Accordingly, the Company has classified these instruments within Level 2 of the hierarchy framework. The Company's derivative financial instruments are recorded at fair market value.

ASC 820 defines fair value as the price that would be received in the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date; requires disclosure of the extent to which fair value is used to measure financial and non-financial assets and liabilities, the inputs utilized in calculating valuation measurements, and the effect of the measurement of significant unobservable inputs on earnings, or changes in net assets, as of the measurement date; and establishes a three-level valuation hierarchy based upon the transparency of inputs utilized in the measurement and valuation of financial assets or liabilities as of the measurement date:

•Level 1 — unadjusted, quoted prices for identical assets or liabilities in active markets;

•Level 2 — quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs other than quoted market prices that are observable or that can be corroborated by observable market data by correlation; and

•Level 3 — unobservable inputs based upon the reporting entity’s internally developed assumptions that market participants would use in pricing the asset or liability.

The Company’s financial instruments consist primarily of cash and cash equivalents, contracts-in-transit and vehicle receivables, accounts and notes receivable, investments in debt and equity securities, accounts payable, credit facilities, long-term debt and interest rate derivative instruments. The fair values of cash and cash equivalents, contracts-in-transit and vehicle receivables, accounts and notes receivable, accounts payable, and credit facilities approximate their carrying values due to the short-term nature of these instruments and/or the existence of variable interest rates. The Company evaluated its assets and liabilities for those that met the criteria of the disclosure requirements and fair value framework of ASC 820 and identified demand obligations, interest rate derivative instruments, and investment balances in certain financial institutions as having met such criteria. See Note 10, "Long-Term Debt" for details regarding the fair value of the Company's long-term debt.

The Company periodically invests in unsecured, corporate demand obligations with manufacturer-affiliated finance companies, which bear interest at a variable rate and are redeemable on demand by the Company. Therefore, the Company has classified these demand obligations as cash and cash equivalents in the accompanying Consolidated Balance Sheets. The Company determined that the valuation measurement inputs of these instruments include inputs other than quoted market prices, that are observable or that can be corroborated by observable data by correlation. Accordingly, the Company has classified these instruments within Level 2 of the hierarchy framework.

In addition, the Company maintains an investment balance with certain of the financial institutions in Brazil that provide credit facilities for the financing of new, used and rental vehicle inventories. The investment balances bear interest at a variable rate and are redeemable by the Company in the future under certain conditions. The Company has classified these investment balances as restricted cash within other assets in the accompanying Consolidated Balance Sheets. The Company determined that the valuation measurement inputs of these instruments include inputs other than quoted market prices, that are observable or that can be corroborated by observable data by correlation. Accordingly, the Company has classified these instruments within Level 2 of the hierarchy framework.

The Company's derivative financial instruments are recorded at fair market value.