Interim Financial Information	6 Months Ended
Interim Financial Information	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
INTERIM FINANCIAL INFORMATION	INTERIM FINANCIAL INFORMATION Business Group 1 Automotive, Inc., a Delaware corporation, (“Group 1” and together with its subsidiaries, the “Company”) is a leading operator in the automotive retailing industry with business activities in 15 states in the United States of America (“U.S.”), 32 towns in the United Kingdom (“U.K.”) and three states in Brazil. The Company, through its three regions, sells new and used cars and light trucks, arranges related vehicle financing, sells service and insurance contracts, provides automotive maintenance and repair services, and sells vehicle parts. As of June 30, 2019, the Company’s U.S. retail network consisted of 116 dealerships within the following states: Alabama, California, Florida, Georgia, Kansas, Louisiana, Maryland, Massachusetts, Mississippi, New Hampshire, New Jersey, New Mexico, Oklahoma, South Carolina, and Texas. The President of U.S. Operations reports directly to the Company’s Chief Executive Officer and is responsible for the overall performance of the U.S. region, as well as overseeing the market directors and dealership general managers. In addition, as of June 30, 2019, the Company had two international regions: (i) the U.K., which consisted of 45 dealerships and (ii) Brazil, which consisted of 17 dealerships. The operations of the Company’s international regions are structured similarly to the U.S. region. The Company’s operating results are generally subject to seasonal variations, as well as changes in the economic environment. In the U.S., we generally experience higher volumes of vehicle sales and service in the second and third calendar quarters of each year. In addition, in some regions of the U.S., vehicle purchases decline during the winter months due to inclement weather. As a result, our U.S. revenues and operating income are typically lower in the first and fourth quarters and higher in the second and third quarters. In the U.K., the first and third quarters tend to be stronger, driven by the vehicle license plate change months of March and September. In Brazil, the first quarter is generally the weakest, driven by more consumer vacations and activities associated with Carnival, while the third and fourth quarters tend to be stronger. Other factors unrelated to seasonality, such as changes in economic conditions, manufacturer incentive programs, supply issues, seasonal weather events and/or changes in currency exchange rates may exaggerate seasonal or cause counter-seasonal fluctuations in the Company’s revenues and operating income. Due to seasonality and other factors, the results of operations for the interim period are not necessarily indicative of the results that will be realized for any other interim period or for the entire fiscal year. Basis of Presentation The accompanying Condensed Consolidated Financial Statements and notes thereto, have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”). Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. Results for interim periods are not necessarily indicative of the results that can be expected for a full year, and therefore should be read in conjunction with the Company’s audited Financial Statements and notes thereto included within the Company’s most recent Annual Report on Form 10-K. Certain reclassifications have been made to prior periods to conform with current period presentation with no effect on the Company’s previously reported consolidated financial position, results of operations or cash flows. These Condensed Consolidated Financial Statements reflect, in the opinion of management, all normal recurring adjustments necessary to fairly state, in all material respects, the Company’s financial position and results of operations for the periods presented. Use of Estimates The preparation of the Company’s financial statements in conformity with U.S. GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the balance sheet date, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from these estimates. Significant estimates made in the accompanying Condensed Consolidated Financial Statements include, but are not limited to, inventory market adjustments, reserves for chargebacks against revenue recognized from the sale of finance and insurance products, reserves for self-insurance programs, certain assumptions related to goodwill and intangible franchise rights, and reserves for potential legal or similar proceedings related to the Company’s business. Recent Accounting Pronouncements Accounting for Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (“Topic 842”), that amends the accounting guidance on leases. The standard establishes a right-of-use (“ROU”) model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. The Company adopted this ASU and all subsequent amendments on January 1, 2019, using the optional transition method applied to leases existing at January 1, 2019, with no restatement of comparative periods. Results for reporting periods beginning after January 1, 2019 are presented under Topic 842, while prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting policies under Accounting Standards Codification (“ASC”) Topic 840, Leases (“ASC 840”). The Company elected the package of practical expedients available under the transition guidance within Topic 842, which among other things, permits the Company to carry forward its historical lease classification. The Company also elected other practical expedients under the transition guidance to (i) not record leases with an initial term of 12 months or less on the balance sheet for all asset classes; (ii) not apply hindsight when determining its lease terms or assessing impairment of its ROU assets during transition; and (iii) combine and account for both lease and non-lease components as a single component for all asset classes, except dealership operating assets. For our dealership operating leases, the Company elected to separate lease and non-lease components and have allocated the consideration between the lease and non-lease components based on the estimated fair value of the leased component. Upon adoption of Topic 842, the Company recognized ROU assets and lease liabilities based on the present value of its remaining minimum rental payments for existing operating leases as of the adoption date, utilizing the Company’s applicable incremental borrowing rate also as of the adoption date. The adoption of Topic 842 resulted in the Company recognizing $222.6 million of operating ROU assets and $236.7 million of operating lease liabilities as of January 1, 2019. The difference between ROU assets and lease liabilities is primarily the result of prepaid rent, favorable lease assets and net unfavorable lease liabilities. Additionally, the Company recognized a $6.1 million cumulative-effect adjustment, net of deferred tax impact, to retained earnings as of January 1, 2019 resulting from the impairment of certain operating ROU assets upon the adoption of Topic 842. The Company’s accounting for its finance leases, previously termed as capital leases under ASC 840, remained substantially unchanged. The adoption of Topic 842 had no material impact on the Company’s condensed consolidated statements of operations or consolidated statements of cash flows. For further details, see Note 11, “Leases”. Credit Losses In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendment in this update replaces the current incurred loss impairment methodology of recognizing credit losses when a loss is probable, with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to assess credit loss estimates. The standard will be effective for fiscal years beginning after December 15, 2019, with early adoption permitted for periods after December 15, 2018. The Company is currently evaluating the impact that the adoption of the provisions of the ASU will have on its consolidated financial statements, but does not expect the impact of the amendment of this ASU to be significant.