Midstream Partnership (Notes)	3 Months Ended
Midstream Partnership (Notes)	Mar. 31, 2013
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments and Joint Ventures Disclosure [Text Block]	Midstream Partnership On March 14, 2013, CenterPoint Energy entered into a Master Formation Agreement with OGE Energy Corp. (OGE) and affiliates of ArcLight Capital Partners, LLC (ArcLight), pursuant to which CenterPoint Energy, OGE and ArcLight agreed to form a midstream partnership (Midstream Partnership) that will initially operate as a private limited partnership. On May 1, 2013, the parties closed on the formation of the Midstream Partnership. In connection with the closing (i) CERC Corp. converted its direct wholly owned subsidiary, CenterPoint Energy Field Services, LLC, a Delaware limited liability company (CEFS), into a Delaware limited partnership that became the Midstream Partnership, (ii) CERC Corp. contributed to the Midstream Partnership its equity interests in each of CenterPoint Energy Gas Transmission Company, LLC (CEGT), CenterPoint Energy - Mississippi River Transmission, LLC (MRT), certain of its other midstream subsidiaries, and a 24.95% interest in Southeast Supply Header, LLC, and (iii) OGE and ArcLight indirectly contributed 100% of the equity interests in Enogex LLC to the Midstream Partnership. The Midstream Partnership is controlled equally by CERC Corp. and OGE.

The entire disclosure for equity method investments and joint ventures. Equity method investments are investments that give the investor the ability to exercise significant influence over the operating and financial policies of an investee. Joint ventures are entities owned and operated by a small group of businesses as a separate and specific business or project for the mutual benefit of the members of the group.

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