Legal Matters	12 Months Ended
Dec. 31, 2017
Loss Contingency [Abstract]
Legal matters	NOTE 14 – LEGAL MATTERS O’Reilly is currently involved in litigation incidental to the ordinary conduct of the Company’s business. The Company accrues for litigation losses in instances where a material adverse outcome is probable and the Company is able to reasonably estimate the probable loss. The Company accrues for an estimate of material legal costs to be incurred in pending litigation matters. Although the Company cannot ascertain the amount of liability that it may incur from any of these matters, it does not currently believe that, in the aggregate, these matters, taking into account applicable insurance and accruals, will have a material adverse effect on its consolidated financial position, results of operations or cash flows in a particular quarter or annual period. As previously reported, on June 18, 2015, a jury in Greene County, Missouri, returned an unfavorable verdict in a litigated contract dispute in the matter Meridian Creative Alliance vs. O’Reilly Automotive Stores, Inc. et. al. in the amount of $12.5 million. As previously reported, the verdict was appealed, reversed in part and remanded to the trial court for a new trial. The matter has been set for trial to commence May 7, 2018, in the Circuit Court of Greene County, Missouri. The Company will continue to vigorously defend the matter. As of December 31, 2017, the Company had accrued $18.6 million with respect to this matter.

NOTE 14 – LEGAL MATTERS

O’Reilly is currently involved in litigation incidental to the ordinary conduct of the Company’s business. The Company accrues for litigation losses in instances where a material adverse outcome is probable and the Company is able to reasonably estimate the probable loss. The Company accrues for an estimate of material legal costs to be incurred in pending litigation matters. Although the Company cannot ascertain the amount of liability that it may incur from any of these matters, it does not currently believe that, in the aggregate, these matters, taking into account applicable insurance and accruals, will have a material adverse effect on its consolidated financial position, results of operations or cash flows in a particular quarter or annual period.

As previously reported, on June 18, 2015, a jury in Greene County, Missouri, returned an unfavorable verdict in a litigated contract dispute in the matter Meridian Creative Alliance vs. O’Reilly Automotive Stores, Inc. et. al. in the amount of $12.5 million. As previously reported, the verdict was appealed, reversed in part and remanded to the trial court for a new trial. The matter has been set for trial to commence May 7, 2018, in the Circuit Court of Greene County, Missouri. The Company will continue to vigorously defend the matter. As of December 31, 2017, the Company had accrued $18.6 million with respect to this matter.