Legal Matters	9 Months Ended
Sep. 30, 2014
Loss Contingency [Abstract]
Legal matters	NOTE 8 – LEGAL MATTERS O’Reilly is currently involved in litigation incidental to the ordinary conduct of the Company’s business. The Company records reserves 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 reserves 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 reserves, will have a material adverse effect on its consolidated financial position, results of operations or cash flows in a particular quarter or annual period. The Company received a subpoena from the District Attorney of the County of Alameda, along with other environmental prosecutorial offices in the state of California, seeking documents and information related to the handling, storage and disposal of hazardous waste. Management has an ongoing and open dialogue with these agencies regarding this matter and is cooperating fully with the request; however, at this time a prediction of the ultimate outcome of these efforts cannot be determined. In addition, O’Reilly was involved in resolving governmental investigations that were being conducted against CSK Auto Corporation ("CSK") and CSK’s former officers and other litigation, prior to its acquisition by O’Reilly in 2008, as described below. As previously reported, the governmental investigations of CSK regarding its legacy pre-acquisition accounting practices have concluded. All criminal charges against former employees of CSK related to its legacy pre-acquisition accounting practices, as well as the civil litigation filed against CSK’s former Chief Executive Officer by the Securities and Exchange Commission (the "SEC"), have concluded. Under Delaware law, the charter documents of the CSK entities, and certain indemnification agreements, CSK may have certain indemnification obligations. As a result of the CSK acquisition, O’Reilly has incurred legal fees and costs related to these potential indemnification obligations arising from the litigation commenced by the Department of Justice and SEC against CSK’s former employees. Whether those legal fees and costs are covered by CSK’s insurance is subject to uncertainty, and, given its complexity and scope, the final outcome cannot be predicted at this time. O’Reilly has a remaining reserve, with respect to the indemnification obligations of $12.1 million at September 30, 2014, which relates to the payment of those legal fees and costs already incurred. It is possible that in a particular quarter or annual period the Company’s results of operations and cash flows could be materially affected by resolution of such matter, depending, in part, upon the results of operations or cash flows for such period. However, at this time, management believes that the ultimate outcome of this matter, after consideration of applicable reserves, should not have a material adverse effect on the Company’s consolidated financial condition, results of operations or cash flows.

NOTE 8 – LEGAL MATTERS

O’Reilly is currently involved in litigation incidental to the ordinary conduct of the Company’s business. The Company records reserves 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 reserves 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 reserves, will have a material adverse effect on its consolidated financial position, results of operations or cash flows in a particular quarter or annual period.

The Company received a subpoena from the District Attorney of the County of Alameda, along with other environmental prosecutorial offices in the state of California, seeking documents and information related to the handling, storage and disposal of hazardous waste. Management has an ongoing and open dialogue with these agencies regarding this matter and is cooperating fully with the request; however, at this time a prediction of the ultimate outcome of these efforts cannot be determined.

In addition, O’Reilly was involved in resolving governmental investigations that were being conducted against CSK Auto Corporation ("CSK") and CSK’s former officers and other litigation, prior to its acquisition by O’Reilly in 2008, as described below.

As previously reported, the governmental investigations of CSK regarding its legacy pre-acquisition accounting practices have concluded. All criminal charges against former employees of CSK related to its legacy pre-acquisition accounting practices, as well as the civil litigation filed against CSK’s former Chief Executive Officer by the Securities and Exchange Commission (the "SEC"), have concluded.

Under Delaware law, the charter documents of the CSK entities, and certain indemnification agreements, CSK may have certain indemnification obligations. As a result of the CSK acquisition, O’Reilly has incurred legal fees and costs related to these potential indemnification obligations arising from the litigation commenced by the Department of Justice and SEC against CSK’s former employees. Whether those legal fees and costs are covered by CSK’s insurance is subject to uncertainty, and, given its complexity and scope, the final outcome cannot be predicted at this time. O’Reilly has a remaining reserve, with respect to the indemnification obligations of $12.1 million at September 30, 2014, which relates to the payment of those legal fees and costs already incurred. It is possible that in a particular quarter or annual period the Company’s results of operations and cash flows could be materially affected by resolution of such matter, depending, in part, upon the results of operations or cash flows for such period. However, at this time, management believes that the ultimate outcome of this matter, after consideration of applicable reserves, should not have a material adverse effect on the Company’s consolidated financial condition, results of operations or cash flows.