Description of Business	3 Months Ended
Description of Business	Mar. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS	NOTE 1 - DESCRIPTION OF BUSINESS Atlas Resources Public #18-2008 (A) L.P. (the “Partnership”) is a Delaware limited partnership, formed on April 8, 2008 with Atlas Resources, LLC serving as its Managing General Partner and Operator (“Atlas Resources” or the “MGP”). Atlas Resources is an indirect subsidiary of Atlas Resource Partners, L.P. (“ARP”) (NYSE: ARP). Unless the context otherwise requires, references to “the Partnership,” “we,” “us” and “our”, refer to Atlas Resources Public #18-2008 (A) L.P. Atlas Energy Group, LLC (“Atlas Energy Group”; OTCQX: ATLS) manages ARP’s operations and activities through its ownership of ARP’s general partner interest. The Partnership has drilled and currently operates wells located in Pennsylvania, Tennessee, Indiana, West Virginia and Ohio. The Partnership has no employees and relies on the MGP for management, which in turn, relies on its parent company, Atlas Energy Group, for administrative services. The Partnership’s operating cash flows are generated from its wells, which produce natural gas, oil and NGL. Produced natural gas, oil and NGL is then delivered to market through affiliated and/or third-party gas gathering systems. The Partnership intends to produce its wells until they are depleted or become uneconomical to produce, at which time they will be plugged and abandoned or sold. The Partnership does not expect to drill additional wells and expects no additional funds will be required for drilling. The economic viability of the Partnership’s production is based on a variety of factors including proved developed reserves that it can expect to recover through existing wells with existing equipment and operating methods or in which the cost of additional required extraction equipment is relatively minor compared to the cost of a new well; and through currently installed extraction equipment and related infrastructure which is operational at the time of the reserves estimate (if the extraction is by means not involving drilling, completing or reworking a well). There are numerous uncertainties inherent in estimating quantities of proven reserves and in projecting future net revenues. The prices at which the Partnership’s natural gas, oil and NGL will be sold are uncertain and the Partnership is not guaranteed a specific price for the sale of its production. Changes in natural gas, oil and NGL prices have a significant impact on the Partnership’s cash flow and the value of its reserves. Lower natural gas, oil and NGL prices may not only decrease the Partnership’s revenues, but also may reduce the amount of natural gas, oil and NGL that the Partnership can produce economically. Liquidity and Capital Resources The Partnership is generally limited to the amount of funds generated by the cash flow from its operations to fund its obligations and make distributions, if any, to its partners. The natural gas, oil and natural gas liquids commodity price markets have suffered significant declines throughout 2015 and have continued to decline and remain low in 2016. The extreme ongoing volatility in the energy industry and commodity prices will likely continue to impact the Partnership’s outlook. The Partnership has experienced downward revisions of its natural gas and oil reserves volumes and values due to the significant declines in commodity prices. The MGP continues to implement various cost saving measures to reduce the Partnership’s operating and general and administrative costs, including renegotiating contracts with contractors, suppliers and service providers, reducing the number of staff and contractors and deferring and eliminating discretionary costs. The MGP will continue to be opportunistic and aggressive in managing the Partnership’s cost structure and, in turn, liquidity to meet its operating needs. To the extent commodity prices remain low or decline further, or the Partnership experiences other disruptions in the industry, the Partnership’s ability to fund its operations and make distributions may be further impacted, and could result in the MGP’s decision to liquidate the Partnership’s operations. Historically, there has been no need to borrow funds from the MGP to fund operations as the cash flow from the Partnership’s operations have been adequate to fund its obligations and distributions to its partners. However, the recent significant declines in commodity prices have challenged the Partnership’s ability to fund its operations and may make it uneconomical for the Partnership to produce its wells until they are depleted as the Partnership originally intended. Accordingly, the MGP determined that there is substantial doubt about the Partnership’s ability to continue as a going concern. The MGP intends, as necessary, to continue the Partnership’s operations and to fund the Partnership’s obligations for at least the next twelve months. The MGP has concluded that such undertaking is sufficient to alleviate the doubt as to the Partnership’s ability to continue as a going concern. To the extent commodity prices remain low or decline further, ARP experiences disruptions in the financial markets impacting its respective longer-term access to or cost of capital, or ARP experiences any of the other impacts to its liquidity discussed below, the MGP’s ability to continue the Partnership’s operations and to fund the Partnership’s obligations for at least the next twelve months, as necessary, may be impacted. ARP’s revolving credit facility is currently in the process of its semi-annual redetermination. Based on projected market conditions, continued declines in commodity prices and recent conversations with its administrative agent, ARP expects that its borrowing base will be redetermined to a level below its outstanding borrowings as of March 31, 2016. If ARP’s borrowing base is redetermined below its current outstanding borrowings and ARP is unable to repay the deficiency or deposit additional collateral to eliminate such deficiency, or if ARP experiences any other event of default on its debt obligations, or if other debt agreements cross-default, and the lenders accelerate the maturity of any other outstanding debts, the MGP, may not have sufficient liquidity to continue the Partnership’s operations and to fund the Partnership’s obligations, and as a result, there would be substantial doubt regarding the Partnership’s ability to continue as a going concern. If, however, the MGP were to decide to liquidate our operations, the liquidation valuation of the Partnership’s assets and liabilities would be determined by an independent expert. It is possible that based on such determination, we would not be able to make any liquidation distributions to our limited partners. A liquidation could result in the transfer of the post-liquidation assets and liabilities of the Partnership to the MGP and would occur without any further contributions from or distributions to the limited partners. The condensed financial statements, which are unaudited, except for the balance sheet at December 31, 2015, which is derived from audited financial statements, have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission and accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim reporting. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to those rules and regulations, although we believe that the disclosures made are adequate to make the information not misleading. These interim financial statements should be read in conjunction with the audited financial statements and notes thereto presented in the Partnership’s Annual Report on Form 10-K for the year ended December 31, 2015. The results of operations for the three months ended March 31, 2016 may not necessarily be indicative of the results of operations for the year ended December 31, 2016.

Atlas Resources Public #18-2008 (A) L.P. 10-Q