Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2017
Summary of Significant Accounting Policies
Basis of Presentation	(a) Basis of Presentation These condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) applicable to interim financial information. The accompanying unaudited condensed financial statements of AMGP have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) for interim financial information, and, accordingly, do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. In the opinion of management, these statements include all adjustments (consisting of normal and recurring accruals) considered necessary for a fair presentation of our financial position as of December 31, 2016 and March 31, 2017, and our results of operations and cash flows for the three months ended March 31, 2016 and 2017. We have no items of other comprehensive income (loss); therefore, our net income (loss) is identical to our comprehensive income (loss). Operating results for the period ended March 31, 2017 are not necessarily indicative of the results that may be expected for the full year. As of the date these condensed consolidated financial statements were filed with the SEC, AMGP completed its evaluation of potential subsequent events for disclosure and no items requiring disclosure were identified.
Principles of Consolidation	(b) Principles of Consolidation The condensed consolidated financial statements include the accounts of Antero Midstream GP LP and its wholly-owned subsidiaries AMP GP and IDR LLC.
Investment in Antero Midstream	(c) Investment in Antero Midstream We have determined that Antero Midstream is a variable interest entity (“VIE”) for which we are not the primary beneficiary and therefore do not consolidate. We have concluded that Antero Resources is the primary beneficiary of Antero Midstream and should consolidate its financial statements. Antero Resources is the primary beneficiary based on its power to direct the activities that most significantly impact Antero Midstream’s economic performance and its obligations to absorb losses or receive benefits of Antero Midstream that could be significant to it. Antero Resources owns approximately 59% of the outstanding limited partner interests in Antero Midstream and its officers and management group also act as management of Antero Midstream. Antero Midstream was formed to own, operate and develop midstream energy assets to service Antero Resources’ production under long term contracts as described herein. We do not own any limited partnership interests in Antero Midstream and have no capital interests in Antero Midstream. We have not provided and do not anticipate providing financial support to Antero Midstream. Antero Resources and Antero Midstream have 20 year contracts with automatic renewal provisions, whereby Antero Resources has dedicated the gathering and compression rights, water delivery and handling services, and gas processing rights to Antero Midstream on a fee basis on all of its current and future acreage, excluding any pre-existing dedications or third-party commitments. The contracts call for Antero Resources to present, in advance, drilling and completion plans in order for Antero Midstream to put in place gathering and compression, water handling, and gas processing assets to service Antero Resources’ assets. The drilling and completion capital investment decisions made by Antero Resources controls the development and operation of all of Antero Midstream’s assets. Antero Resources therefore controls the activities that most significantly impact Antero Midstream’s economic performance. Because of these contractual obligations and the capital requirements related to these obligations, Antero Midstream has and will devote substantially all of its resources to servicing Antero Resources’ operations and revenues from Antero Resources will provide substantially all of Antero Midstream’s financial support and therefore its ability to finance its operations. Because of the long term contractual commitment to support Antero Resources’ substantial growth plans, Antero Midstream will be practically and physically constrained from providing any substantive amount of services to third parties. Our ownership of the non-economic general partner interest in Antero Midstream provides us with significant influence over Antero Midstream, but not control over the decisions that most significantly impact the economic performance of Antero Midstream. Our ownership of IDRs of Antero Midstream entitles us to receive cash distributions from Antero Midstream when distributions exceed certain target amounts. The ownership of these interests and IDRs do not require us to provide financial support to Antero Midstream. We obtained these interests upon our formation for no consideration. Therefore, they have no cost basis and are classified as long term investments. Our share of Antero Midstream’s earnings as a result of our ownership of IDRs is accounted for using the equity method of accounting. We recognize distributions earned from Antero Midstream as “Equity in earnings of Antero Midstream Partners LP” on our statement of operations in the period to which they are earned and are allocated to our capital account. Our long term interest in IDRs on the balance sheet is recorded in “Investment in Antero Midstream Partners LP.” The ownership of the general partner interests and IDRs do not provide us with any claim to the assets of Antero Midstream other than the balance in our Antero Midstream capital account. Distributions are recognized as earned and increase our capital account and equity investment. When these distributions are paid to us they reduce our capital accounts and our equity investment in Antero Midstream. See Note 4—Distributions from Antero Midstream.
Use of Estimates	(d) Use of Estimates The preparation of the condensed consolidated financial statements and notes in conformity with GAAP requires that management formulate estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates.
Income Taxes	(e) Income Taxes We regularly review our tax positions in each significant taxing jurisdiction in the process of evaluating our tax provision. We make adjustments to our tax provision when: (i) facts and circumstances regarding a tax position change, causing a change in management’s judgment regarding that tax position; and/or (ii) a tax position is effectively settled with a tax authority at a differing amount. The difference between income tax expense and expected income tax expense computed by applying the federal statutory rate of 35% to pretax income is caused by nondeductible equity-based compensation and IPO expenses, as well as state income taxes.
General and Administrative Expenses	(f) General and Administrative Expenses General and administrative costs incurred during 2016 and 2017 relate to legal and other costs incurred in connection with our IPO.

Disclosure of accounting policy for the equity method of accounting for investments in common stock or other interests including unconsolidated subsidiaries, corporate joint ventures, noncontrolling interests in real estate ventures, limited partnerships, and limited liability companies. The accounting policy may include information such as: (1) initially recording an investment in the stock of an investee at cost; (2) adjusting the carrying amount of the investment to recognize the investor's share of the earnings or losses of the investee after the date of acquisition; and (3) adjustments to reflect the investor's share of changes in the investee's capital (dividends). This disclosure may also include a detailed description of the policy for determining the amount of equity method losses recognized after an investment has been reduced to zero as a result of previous losses, reasons for not using the equity method when the investor company owns 20 percent or more of the voting stock of the investee's company (including identification of the significant investee), reasons for using the equity method when the ownership percentage is less than 20 percent, and discussion of recognition of equity method losses when an investor's total investment in an investee includes, in addition to an investment in common stock, other investments such as preferred stock and loans to the investee. An entity also may describe how such investments are assessed for impairment.

- Definition

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

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