Organization and Basis of Presentation	9 Months Ended
Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	ORGANIZATION AND BASIS OF PRESENTATION Energen Corporation (Energen or the Company) is an oil and natural gas exploration and production company engaged in the exploration, development and production of oil, natural gas liquids and natural gas. Our operations are conducted through our subsidiary, Energen Resources Corporation (Energen Resources) and primarily occur within the Midland Basin, the Delaware Basin and the Central Basin Platform areas of the Permian Basin in west Texas and New Mexico. Our corporate headquarters is located in Birmingham, Alabama. The unaudited consolidated financial statements and notes should be read in conjunction with the consolidated financial statements and notes thereto included in the 2017 Annual Report of Energen on Form 10-K. Our accompanying unaudited consolidated financial statements include Energen and its subsidiaries, principally Energen Resources, and have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the disclosures required for complete financial statements. Results of operations for interim periods are not necessarily indicative of the results that may be expected for the year. In the opinion of management, the accompanying consolidated financial statements reflect all adjustments necessary to present a fair statement of our financial position, results of operations, and cash flows for the periods and as of the dates shown. Such adjustments consist of normal recurring items. Certain reclassifications were made to conform prior periods’ financial statements to the current-quarter presentation. Proposed Merger of Energen with Diamondback Energy, Inc. (Diamondback) On August 14, 2018, Energen entered into an Agreement and Plan of Merger (the Merger Agreement) with Diamondback and Sidewinder Merger Sub Inc., a wholly owned subsidiary of Diamondback (Merger Sub). The closing of the Merger (as defined below) is expected to occur in the fourth quarter of 2018. The Merger Agreement provides that, among other things and subject to the terms and conditions of the Merger Agreement, (1) Merger Sub will be merged with and into Energen (the Merger), with Energen surviving and continuing as the surviving corporation in the Merger, and, (2) at the effective time of the Merger (the Effective Time), each outstanding share of common stock of Energen (other than shares held in treasury by Energen, shares owned by Diamondback or Merger Sub or shares with respect to which dissenters’ rights have been validly exercised in accordance with Alabama law) will be converted into the right to receive 0.6442 of a share of common stock of Diamondback, plus cash in lieu of any fractional shares that otherwise would have been issued (the Merger Consideration). Diamondback’s common stock is listed and traded on NASDAQ under the ticker symbol FANG. The completion of the Merger is subject to satisfaction or waiver of certain customary mutual closing conditions, including (1) the receipt of the required approvals from Energen shareholders and Diamondback stockholders, (2) the expiration or termination of the waiting period under the Hart-Scott-Rodino Act, as amended (which termination was received on September 10, 2018), (3) the absence of any governmental order or law that makes consummation of the Merger illegal or otherwise prohibited, (4) the effectiveness of the registration statement on Form S-4 to be filed by Diamondback pursuant to which the shares of Diamondback common stock to be issued in connection with the merger are registered with the Securities and Exchange Commission (the SEC), (5) the authorization for listing of Diamondback common stock to be issued in connection with the merger on the NASDAQ and (6) the receipt by each party of a customary opinion that the Merger will qualify as a “reorganization” within the meaning of Section 368(a) of the U.S. tax code. The obligation of each party to consummate the Merger is also conditioned upon the other party’s representations and warranties being true and correct (subject to certain materiality exceptions) and the other party having performed in all material respects its obligations under the Merger Agreement. The Merger Agreement contains termination rights for each of Diamondback and Energen, including, among others, (1) if the consummation of the Merger does not occur on or before March 31, 2019, subject to extension to June 30, 2019 for the sole purpose of obtaining regulatory clearances and (2) subject to certain conditions, if such party wishes to terminate the Merger Agreement to enter into a definitive agreement with respect to a Parent Superior Proposal or a Company Superior Proposal (in each case, as such term is defined in the Merger Agreement), as applicable. Upon termination of the Merger Agreement under specified circumstances, including the termination by Energen in the event of a change of recommendation by the Diamondback board of directors or by Diamondback to enter into an agreement providing for a Parent Superior Proposal (as such term is defined in the Merger Agreement), Diamondback would be required to pay Energen a termination fee of $400 million. In addition, upon termination of the Merger Agreement under specified circumstances, including the termination by Diamondback in the event of a change of recommendation by the Energen board of directors or by Energen to enter into an agreement providing for a Company Superior Proposal (as such term is defined in the Merger Agreement), Energen would be required to pay Diamondback a termination fee of $250 million. In addition, if the Merger Agreement is terminated because of a failure of Energen’s shareholders or Diamondback’s stockholders to approve the proposals required to complete the Merger, Energen and Diamondback, as applicable, may be required to reimburse the other party for its actual transaction expenses in an amount not to exceed $40 million, in the case of Energen’s expenses, and $25 million, in the case of Diamondback’s expenses. In no event will either party be entitled to receive more than one termination fee, net of any expense reimbursement. In connection with the Merger, Diamondback filed with the SEC, on October 18, 2018, an amendment to the registration statement on Form S-4 that was originally filed on September 13, 2018, that includes a joint proxy statement of Energen and Diamondback. The joint proxy statement also constitutes a prospectus for Diamondback with respect to the shares of Diamondback common stock to be issued as Merger Consideration. The registration statement was declared effective by the SEC on October 24, 2018, and Energen and Diamondback commenced mailing the definitive joint proxy statement/prospectus to Energen shareholders and Diamondback stockholders on or about October 26, 2018. Additional information on the proposed Merger is included in the registration statement on Form S-4/A filed by Diamondback with the SEC on October 18, 2018.

ORGANIZATION AND BASIS OF PRESENTATION

Energen Corporation (Energen or the Company) is an oil and natural gas exploration and production company engaged in the exploration, development and production of oil, natural gas liquids and natural gas. Our operations are conducted through our subsidiary, Energen Resources Corporation (Energen Resources) and primarily occur within the Midland Basin, the Delaware Basin and the Central Basin Platform areas of the Permian Basin in west Texas and New Mexico. Our corporate headquarters is located in Birmingham, Alabama. The unaudited consolidated financial statements and notes should be read in conjunction with the consolidated financial statements and notes thereto included in the 2017 Annual Report of Energen on Form 10-K.

Our accompanying unaudited consolidated financial statements include Energen and its subsidiaries, principally Energen Resources, and have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the disclosures required for complete financial statements. Results of operations for interim periods are not necessarily indicative of the results that may be expected for the year. In the opinion of management, the accompanying consolidated financial statements reflect all adjustments necessary to present a fair statement of our financial position, results of operations, and cash flows for the periods and as of the dates shown. Such adjustments consist of normal recurring items. Certain reclassifications were made to conform prior periods’ financial statements to the current-quarter presentation.

Proposed Merger of Energen with Diamondback Energy, Inc. (Diamondback)

On August 14, 2018, Energen entered into an Agreement and Plan of Merger (the Merger Agreement) with Diamondback and Sidewinder Merger Sub Inc., a wholly owned subsidiary of Diamondback (Merger Sub). The closing of the Merger (as defined below) is expected to occur in the fourth quarter of 2018.

The Merger Agreement provides that, among other things and subject to the terms and conditions of the Merger Agreement, (1) Merger Sub will be merged with and into Energen (the Merger), with Energen surviving and continuing as the surviving corporation in the Merger, and, (2) at the effective time of the Merger (the Effective Time), each outstanding share of common stock of Energen (other than shares held in treasury by Energen, shares owned by Diamondback or Merger Sub or shares with respect to which dissenters’ rights have been validly exercised in accordance with Alabama law) will be converted into the right to receive 0.6442 of a share of common stock of Diamondback, plus cash in lieu of any fractional shares that otherwise would have been issued (the Merger Consideration). Diamondback’s common stock is listed and traded on NASDAQ under the ticker symbol FANG.

The completion of the Merger is subject to satisfaction or waiver of certain customary mutual closing conditions, including (1) the receipt of the required approvals from Energen shareholders and Diamondback stockholders, (2) the expiration or termination of the waiting period under the Hart-Scott-Rodino Act, as amended (which termination was received on September 10, 2018), (3) the absence of any governmental order or law that makes consummation of the Merger illegal or otherwise prohibited, (4) the effectiveness of the registration statement on Form S-4 to be filed by Diamondback pursuant to which the shares of Diamondback common stock to be issued in connection with the merger are registered with the Securities and Exchange Commission (the SEC), (5) the authorization for listing of Diamondback common stock to be issued in connection with the merger on the NASDAQ and (6) the receipt by each party of a customary opinion that the Merger will qualify as a “reorganization” within the meaning of Section 368(a) of the U.S. tax code. The obligation of each party to consummate the Merger is also conditioned upon the other party’s representations and warranties being true and correct (subject to certain materiality exceptions) and the other party having performed in all material respects its obligations under the Merger Agreement.

The Merger Agreement contains termination rights for each of Diamondback and Energen, including, among others, (1) if the consummation of the Merger does not occur on or before March 31, 2019, subject to extension to June 30, 2019 for the sole purpose of obtaining regulatory clearances and (2) subject to certain conditions, if such party wishes to terminate the Merger Agreement to enter into a definitive agreement with respect to a Parent Superior Proposal or a Company Superior Proposal (in each case, as such term is defined in the Merger Agreement), as applicable. Upon termination of the Merger Agreement under specified circumstances, including the termination by Energen in the event of a change of recommendation by the Diamondback board of directors or by Diamondback to enter into an agreement providing for a Parent Superior Proposal (as such term is defined in the Merger Agreement), Diamondback would be required to pay Energen a termination fee of $400 million. In addition, upon termination of the Merger Agreement under specified circumstances, including the termination by Diamondback in the event of a change of recommendation by the Energen board of directors or by Energen to enter into an agreement providing for a Company Superior Proposal (as such term is defined in the Merger Agreement), Energen would be required to pay Diamondback a termination fee of $250 million. In addition, if the Merger Agreement is terminated because of a failure of Energen’s shareholders or Diamondback’s stockholders to approve the proposals required to complete the Merger, Energen and Diamondback, as applicable, may be required to reimburse the other party for its actual transaction expenses in an amount not to exceed $40 million, in the case of Energen’s expenses, and $25 million, in the case of Diamondback’s expenses. In no event will either party be entitled to receive more than one termination fee, net of any expense reimbursement.

In connection with the Merger, Diamondback filed with the SEC, on October 18, 2018, an amendment to the registration statement on Form S-4 that was originally filed on September 13, 2018, that includes a joint proxy statement of Energen and Diamondback. The joint proxy statement also constitutes a prospectus for Diamondback with respect to the shares of Diamondback common stock to be issued as Merger Consideration. The registration statement was declared effective by the SEC on October 24, 2018, and Energen and Diamondback commenced mailing the definitive joint proxy statement/prospectus to Energen shareholders and Diamondback stockholders on or about October 26, 2018.

Additional information on the proposed Merger is included in the registration statement on Form S-4/A filed by Diamondback with the SEC on October 18, 2018.