Acquisition and Disposition of Properties	6 Months Ended
Jun. 30, 2017
Business Combinations [Abstract]
Acquisition and Disposition of Properties	ACQUISITION AND DISPOSITION OF PROPERTIES During the six months ended June 30, 2017, Energen completed an estimated total of $235.6 million in various purchases and renewals of unproved acquisitions including approximately $185.9 million in the Delaware Basin and approximately $30.9 million in the Midland Basin for unproved leasehold and $18.8 million for mineral purchases in the Delaware Basin. During the six months ended June 30, 2016, Energen completed an estimated $27.2 million in various purchases and renewals of unproved leasehold largely in the Permian Basin. During June, July and August of 2016, Energen completed a series of asset sales of certain non-core Permian Basin assets in the Delaware Basin in Texas and in the San Juan Basin in New Mexico for an aggregate purchase price of $552 million. These transactions had closing dates of June 3, 7, 30, July 15 and August 9 of 2016 with various effective dates ranging from March 1, 2016 to June 30, 2016. Minor portions of the assets were transferred to other parties upon the exercise of preferential purchase rights under pre-existing joint operating agreements in the ordinary course of business. Pre-tax proceeds to Energen were approximately $532.5 million after purchase price adjustments of approximately $19 million related to the operations of the properties subsequent to the effective dates and other one-time adjustments including transfer payments and certain amounts due the buyer, but before consideration of transaction costs of approximately $5 million. Energen recognized total net pre-tax gains of approximately $246 million on the sales. Energen used proceeds from the sale to fund ongoing operations. For the six months ended June 30, 2017, included in the net (gain) loss on sale of assets and other, Energen recognized post-closing adjustment losses of $0.2 million on these sales. For the six months ended June 30, 2016, Energen recognized pre-tax gains of $161.1 million on the sales closed through June 30, 2016.

ACQUISITION AND DISPOSITION OF PROPERTIES

During the six months ended June 30, 2017, Energen completed an estimated total of $235.6 million in various purchases and renewals of unproved acquisitions including approximately $185.9 million in the Delaware Basin and approximately $30.9 million in the Midland Basin for unproved leasehold and $18.8 million for mineral purchases in the Delaware Basin. During the six months ended June 30, 2016, Energen completed an estimated $27.2 million in various purchases and renewals of unproved leasehold largely in the Permian Basin.

During June, July and August of 2016, Energen completed a series of asset sales of certain non-core Permian Basin assets in the Delaware Basin in Texas and in the San Juan Basin in New Mexico for an aggregate purchase price of $552 million. These transactions had closing dates of June 3, 7, 30, July 15 and August 9 of 2016 with various effective dates ranging from March 1, 2016 to June 30, 2016. Minor portions of the assets were transferred to other parties upon the exercise of preferential purchase rights under pre-existing joint operating agreements in the ordinary course of business. Pre-tax proceeds to Energen were approximately $532.5 million after purchase price adjustments of approximately $19 million related to the operations of the properties subsequent to the effective dates and other one-time adjustments including transfer payments and certain amounts due the buyer, but before consideration of transaction costs of approximately $5 million. Energen recognized total net pre-tax gains of approximately $246 million on the sales. Energen used proceeds from the sale to fund ongoing operations. For the six months ended June 30, 2017, included in the net (gain) loss on sale of assets and other, Energen recognized post-closing adjustment losses of $0.2 million on these sales. For the six months ended June 30, 2016, Energen recognized pre-tax gains of $161.1 million on the sales closed through June 30, 2016.