SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES | Apache Offshore Investment Partnership, a Delaware general partnership (the Investment Partnership), was formed on October 31, 1983, consisting of Apache Corporation, a Delaware corporation (Apache or the Managing Partner), as Managing Partner and public investors (the Investing Partners). The Investment Partnership invested its entire capital in Apache Offshore Petroleum Limited Partnership, a Delaware limited partnership (the Operating Partnership). The primary business of the Investment Partnership is to serve as the sole limited partner of the Operating Partnership. The accompanying financial statements include the accounts of both the Investment Partnership and the Operating Partnership. The term “Partnership,” as used herein, refers to the Investment Partnership or the Operating Partnership, as the case may be. These financial statements have been prepared by the Partnership, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). They reflect all adjustments that are, in the opinion of management, necessary for a fair statement of the results for the interim periods, on a basis consistent with the annual audited financial statements, with the exception of recently adopted accounting pronouncements discussed below. All such adjustments are of a normal, recurring nature. Certain information, accounting policies, and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) have been omitted pursuant to such rules and regulations, although the Partnership believes that the disclosures are adequate to make the information presented not misleading. These financial statements should be read in conjunction with the Partnership’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 , which contains a summary of the Partnership’s significant accounting policies and other disclosures. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES As of March 31, 2018 , the Partnership’s significant accounting policies are consistent with those discussed in Note 2 of its consolidated financial statements contained in the Annual Report on Form 10-K for the fiscal year ended December 31, 2017 with the exception of Accounting Standards Update (ASU) 2014-09, “Revenue from Contracts with Customers (Topic 606)” (see “Revenue Recognition” section in this Note 1 below). Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates with regard to these financial statements include the estimate of proved oil and gas reserve quantities and the related present value of estimated future net cash flows therefrom and the assessment of asset retirement obligations. Actual results could differ from those estimates. Oil and Gas Property The Partnership follows the full-cost method of accounting for its oil and gas property. Under this method of accounting, all costs incurred for both successful and unsuccessful exploration and development activities, and oil and gas property acquisitions are capitalized. The net book value of oil and gas properties may not exceed a calculated “ceiling.” The ceiling limitation is the estimated future net cash flows from proved oil and gas reserves, discounted at 10 percent per annum. Estimated future net cash flows are calculated using end-of-period costs and an unweighted arithmetic average of commodity prices in effect on the first day of each of the previous 12 months, held flat for the life of the production, except where prices are defined by contractual arrangements. For a discussion of the calculation of estimated future net cash flows, please refer to Note 10—Supplemental Oil and Gas Disclosures to the consolidated financial statements contained in the Partnership’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 . Any excess of the net book value of proved oil and gas properties over the ceiling is charged to expense and reflected as “Additional depreciation, depletion and amortization” in the accompanying statement of consolidated operations. Such limitations are tested quarterly. The Partnership had no non-cash write-downs of the carrying value of its proved oil and gas properties during the first quarters of 2018 and 2017. Revenue Recognition On January 1, 2018, the Partnership adopted Accounting Standards Update (ASU) 2014-09, “Revenue from Contracts with Customers (ASC 606),” using the modified retrospective method. The Partnership elected to evaluate all contracts at the date of initial application. There was no impact to the opening balance of retained earnings as a result of the adoption, and the new standard is not anticipated to impact the Partnership’s net earnings on an ongoing basis. The Partnership applies the provisions of ASC 606 for revenue recognition to contracts with customers. Sales of crude oil, natural gas, and natural gas liquids (NGLs) are included in revenue when production is sold to a customer in fulfillment of performance obligations under the terms of agreed contracts. Performance obligations primarily comprise delivery of oil, gas, or NGLs at a delivery point, as negotiated within each contract. Each barrel of oil, MMBtu of natural gas, or other unit of measure is separately identifiable and represents a distinct performance obligation to which the transaction price is allocated. Performance obligations are satisfied at a point in time once control of the product has been transferred to the customer. The Partnership considers a variety of facts and circumstances in assessing the point of control transfer, including but not limited to: whether the purchaser can direct the use of the hydrocarbons, the transfer of significant risks and rewards, the Partnership’s right to payment, and transfer of legal title. In each case, the term between delivery and when payments are due is not significant. For the three months ended March 31, 2018 , revenues from customers totaled $354,408 . Apache, as Managing Partner of the Partnership, markets the Partnership's share of oil production from South Timbalier 295, the Partnership's largest source of production. The Partnership markets all other production under the joint operating agreements with the operator of its properties. The operator seeks and negotiates oil and gas marketing arrangements with various marketers and purchasers. These contracts provide for sales that are priced at prevailing market prices. Apache primarily markets to major oil companies, marketing and transportation companies, and refiners at current index prices, adjusted for quality, transportation, and market reflective differentials. The Partnership records trade accounts receivable for its unconditional rights to consideration arising under sales contracts with customers. The carrying value of such receivables, net of the allowance for doubtful accounts, represents estimated net realizable value. The Partnership routinely assesses the collectability of all material trade and other receivables. The Partnership accrues a reserve on a receivable when, based on the judgment of management, it is probable that a receivable will not be collected and the amount of any reserve may be reasonably estimated. As of March 31, 2018, the carrying amounts of trade accounts receivables approximate fair value because of the short-term nature of these instruments. Receivables from contracts with customers, net of allowance for doubtful accounts, totaled $125,525 and $92,881 as of March 31, 2018 and December 31, 2017 , respectively. The Partnership has concluded that disaggregating revenue by product appropriately depicts how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. Total revenues for oil, gas, and NGLs were $314,487 , $31,125 , and $8,796 , respectively, for the three months ended March 31, 2018 . Revenues for oil, gas, and NGLs were $261,166 , $61,165 , and $3,978 , respectively, for the three months ended March 31, 2017 . Practical Expedients and Exemptions The Partnership does not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less or contracts for which variable consideration is allocated entirely to a wholly unsatisfied performance obligation. The Partnership will utilize the practical expedient to expense incremental costs of obtaining a contract if the expected amortization period is one year or less. Costs to obtain a contract with expected amortization periods of greater than one year will be recorded as an asset and will be recognized in accordance with ASC 340, “Other Assets and Deferred Costs.” Currently, the Partnership does not have contract assets related to incremental costs to obtain a contract. New Pronouncements Issued But Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842),” requiring lessees to recognize lease assets and lease liabilities for most leases classified as operating leases under previous U.S. GAAP. The guidance is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted; however, the Partnership does not intend to early adopt. The Partnership is currently evaluating the impact of adopting this standard on its consolidated financial statements. In January 2018, the FASB issued a proposed ASU update that would add a transition option permitting entities to apply the provisions of the new standard at its adoption date instead of the earliest comparative period presented in the consolidated financial statements. If finalized, comparative reporting would not be required and the provisions of the standard would be applied prospectively to leases in effect at date of adoption. The Partnership is currently evaluating the impact of adopting this standard on its consolidated financial statements. |