Acquisitions (Other Acquisition) (Narrative) (Details) - USD ($) $ in Millions						1 Months Ended				3 Months Ended		12 Months Ended
	Oct. 01, 2015	Jul. 08, 2015	Jun. 05, 2015	Nov. 05, 2014	May 12, 2014	Sep. 30, 2015	Dec. 31, 2014	Oct. 31, 2014	Mar. 31, 2014	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Arkoma Acquisition | Predecessor
Business Acquisition [Line Items]
Cash Consideration			$ 31.5
Issuances of Partnership Units to Fund the Purchase Price			6,500,000
Business Acquisition, Effective Date of Acquisition			Jan. 01, 2015
Eagle Ford Acquisition | Atlas Growth Partners L P
Business Acquisition [Line Items]
Deferred portion of purchase price				$ 19.9						$ 16.0	$ 28.3
Eagle Ford Acquisition | Predecessor
Business Acquisition [Line Items]
Cash Consideration				183.1
Business Acquisition, Date of Acquisition Agreement												Nov. 05, 2014
Net cash acquired				342.0
Deferred portion of purchase price				$ 139.0
Eagle Ford Acquisition | Predecessor | Class D Preferred Units
Business Acquisition [Line Items]
Issuances of Partnership Units to Fund the Purchase Price								3,200,000			800,000
Eagle Ford Acquisition | Predecessor | Atlas Growth Partners L P
Business Acquisition [Line Items]
Cash Consideration		$ 1.4
Deferred portion of purchase price						$ 36.3	$ 35.0
Eagle Ford Acquisition | Predecessor | Atlas Resource Partners, L.P.
Business Acquisition [Line Items]
Deferred portion of purchase price	$ 17.5									$ 0.6			$ 21.6
Eagle Ford Acquisition | Predecessor | Atlas Resource Partners, L.P. | Class D Preferred Units
Business Acquisition [Line Items]
Deferred portion of purchase price by issuing preferred units											$ 20.0
GeoMet Acquisition | Predecessor
Business Acquisition [Line Items]
Cash Consideration					$ 97.9
Issuances of Partnership Units to Fund the Purchase Price									6,325,000
Business Acquisition, Effective Date of Acquisition					Jan. 01, 2014
Business Acquisition, Description of Acquired Entity												The assets included coal-bed methane producing natural gas assets in West Virginia and Virginia.