OGE Energy Midstream Partnership with CenterPoint Energy, Inc.	3 Months Ended
Mar. 31, 2013
OGE Energy Midstream Partnership with CenterPoint Energy Inc. [Abstract]
Equity Method Investments and Joint Ventures Disclosure [Text Block]	OGE Energy Midstream Partnership with CenterPoint Energy, Inc. On March 14, 2013, OGE Energy entered into a Master Formation Agreement with the ArcLight group and CenterPoint Energy, Inc., pursuant to which OGE Energy, the ArcLight group and CenterPoint Energy, Inc., agreed to form the Midstream Partnership to own and operate the midstream businesses of OGE Energy and CenterPoint that will initially be structured as a private limited partnership. This transaction closed on May 1, 2013. Pursuant to the Master Formation Agreement, OGE Energy and the ArcLight group indirectly contributed 100 percent of the equity interests in Enogex LLC to the Midstream Partnership. CenterPoint Energy Field Services, LLC, a Delaware limited liability company and wholly owned subsidiary of CenterPoint, was converted into a Delaware limited partnership that became the Midstream Partnership. CenterPoint contributed to the Midstream Partnership its equity interests in each of CenterPoint Energy Gas Transmission Company, LLC, a Delaware limited liability company, CenterPoint Energy - Mississippi River Transmission, LLC, a Delaware limited liability company, and certain of its other midstream subsidiaries and caused its subsidiary CenterPoint Energy Southeastern Pipelines Holding, LLC to contribute 49 percent of its interest in Southeast Supply Header, LLC, a Delaware limited liability company. CenterPoint Energy Field Services, LLC provides natural gas gathering and processing services for certain natural gas fields in the Mid-continent region of the United States that interconnect with CenterPoint Energy Gas Transmission Company, LLC and CenterPoint Energy - Mississippi River Transmission, LLC pipelines, as well as other interstate and intrastate pipelines. As of December 31, 2012, CenterPoint Energy Field Services, LLC gathered an average of approximately 2.5 billion cubic feet per day of natural gas. In addition, CenterPoint Energy Field Services, LLC has the capacity available to treat up to 2.5 billion cubic feet per day and process nearly 625 million cubic feet per day of natural gas. CenterPoint Energy Gas Transmission Company, LLC is an interstate pipeline that provides natural gas transportation, storage and pipeline services to customers principally in Arkansas, Louisiana, Oklahoma and Texas and includes the 1.9 billion cubic feet per day pipeline from Carthage, Texas to Perryville, Louisiana, which CenterPoint Energy Gas Transmission Company, LLC operates as a separate line with a fixed fuel rate. CenterPoint Energy - Mississippi River Transmission, LLC is an interstate pipeline that provides natural gas transportation, storage and pipeline services to customers principally in Arkansas, Illinois and Missouri. CenterPoint indirectly owns a 50 percent interest in Southeast Supply Header, LLC, which owns a 1.0 billion cubic feet per day, 274-mile interstate pipeline that runs from the Perryville Hub in Louisiana to Coden, Alabama. A wholly owned indirect subsidiary of Spectra Energy Corp. owns the remaining 50 percent interest in Southeast Supply Header, LLC. Upon closing, CenterPoint indirectly contributed 49 percent of its interest in the Southeast Supply Header, LLC to the Midstream Partnership. Upon receipt of certain consents, CenterPoint will contribute the remainder of its interest to the Midstream Partnership. Immediately prior to closing, on May 1, 2013, the ArcLight group contributed $107.0 million and OGE Energy contributed $9.1 million to Enogex LLC in order to pay down short-term debt. At May 1, 2013, OGE Energy holds 28.5 percent of the limited partners interests, CenterPoint holds 58.3 percent of the limited partner interests and the ArcLight group holds 13.2 percent of the limited partner interests in the Midstream Partnership, provided, however, if CenterPoint obtains the approvals required to contribute its remaining indirect interest in Southeast Supply Header, LLC within 90 days after closing, CenterPoint will instead hold 59 percent of the limited partner interests, OGE would hold 28 percent of the limited partners interest and the ArcLight group would hold 13 percent of the limited partners interest. After the expiration of the 90-day period after closing, CenterPoint has certain put rights, and the Midstream Partnership has certain call rights, exercisable with respect to any interest in Southeast Supply Header, LLC retained by CenterPoint following the formation of the Midstream Partnership, under which CenterPoint would contribute to the Midstream Partnership CenterPoint's retained interest in Southeast Supply Header, LLC at a price equal to the fair market value of such interest at the time the put right or call right is exercised. If CenterPoint were to exercise such put right or the Midstream Partnership were to exercise such call right, CenterPoint's retained interest in Southeast Supply Header, LLC would be contributed to the Midstream Partnership in exchange for consideration consisting of a specified number of limited partnership units and, subject to certain restrictions, a cash payment, payable either from CenterPoint to the Midstream Partnership or from the Midstream Partnership to CenterPoint, in an amount such that the total consideration exchanged is equal in value to the fair market value of the contributed interest in Southeast Supply Header, LLC. The general partner of the Midstream Partnership is equally controlled by CenterPoint and OGE Energy, who each have 50 percent of the management rights. CenterPoint and OGE Energy also own a 40 percent and 60 percent interest, respectively, in any incentive distribution rights to be held by the general partner of the Midstream Partnership following an initial public offering of the Midstream Partnership. In addition, for a period of time, the ArcLight group will have board observation rights and approval rights over certain material activities of the Midstream Partnership, including material increases in capital expenditures and certain equity issuances, entering into transactions with related parties and acquiring, pledging or disposing of certain material assets. The general partner of the Midstream Partnership will initially be governed by a board made up of an equal number of representatives designated by each of CenterPoint Energy, Inc. and OGE Energy. Based on the 50/50 management ownership, with neither company having control, effective May 1, 2013, OGE Energy deconsolidated its interest in Enogex LLC and will account for its interest in the Midstream Partnership under the equity method of accounting. Pursuant to a Registration Rights Agreement dated as of May 1, 2013, OGE Energy and CenterPoint Energy, Inc. agreed to initiate the process for the sale of an equity interest in the Midstream Partnership in an initial public offering. OGE Energy can give no assurances that the initial public offering will be consummated. Prior to consummating the initial public offering, OGE Energy, CenterPoint Energy, Inc. and the Midstream Partnership will need to complete the negotiation of the financial and other terms, including the initial public offering price. In addition, consummation of the initial public offering is subject to market conditions. For so long as the ArcLight group maintains a minimum ownership percentage, the ArcLight group is entitled to consult with the Midstream Partnership in connection with the initial public offering. The Midstream Partnership has agreed to file a registration statement for the initial public offering no later than May 1, 2014 and, subject to limited exceptions, consummate the initial public offering within 180 days of the filing of the registration statement. In connection with the formation of the Midstream Partnership, on May 1, 2013, the Midstream Partnership entered into a $1.05 billion three-year senior unsecured term loan facility, the proceeds of which were used to repay $1.05 billion of intercompany indebtedness owed to CenterPoint. CenterPoint has guaranteed collection of the Midstream Partnership's obligations under the term loan, which guarantee is subordinated to all senior debt of CenterPoint. Effective May 1, 2013, the Midstream Partnership also entered into a $1.4 billion, five-year senior unsecured revolving credit facility in accordance with the terms of the Master Formation Agreement and Enogex LLC's $400 million revolving credit facility was terminated. At March 31, 2013, Enogex LLC was obligated on approximately $700 million, in the aggregate, in indebtedness under its term loan, its revolving credit agreement and two series of its senior notes maturing in years 2014 and 2020. Certain of the entities contributed to the Midstream Partnership by CenterPoint are obligated on approximately $363 million of indebtedness owed to a wholly owned subsidiary of CenterPoint that is scheduled to mature in 2017. Subject to the exceptions provided below, pursuant to the terms of an Omnibus Agreement dated as of May 1, 2013 among OGE Energy, the ArcLight group and CenterPoint Energy, Inc., each of OGE Energy and CenterPoint Energy, Inc. will be required to hold or otherwise conduct all of its respective Midstream Operations (as defined below) located within the United States in the Midstream Partnership. This restriction will cease to apply to both OGE Energy and CenterPoint Energy, Inc. as soon as either OGE Energy or CenterPoint Energy, Inc. ceases to hold (i) any interest in the general partner of the Midstream Partnership or (ii) at least 20 percent of the limited partner interests of the Midstream Partnership. "Midstream Operations" generally means, subject to certain exceptions, the gathering, compression, treatment, processing, blending, transportation, storage, isomerization and fractionation of crude oil and natural gas, its associated production water and enhanced recovery materials such as carbon dioxide, and its respective constituents and the following products: methane, NGLs (Y-grade, ethane, propane, normal butane, isobutane and natural gasoline), condensate, and refined products and distillates (gasoline, refined product blendstocks, olefins, naphtha, aviation fuels, diesel, heating oil, kerosene, jet fuels, fuel oil, residual fuel oil, heavy oil, bunker fuel, cokes, and asphalts), to the extent such activities are located within the United States. In addition, if OGE Energy or CenterPoint Energy, Inc. acquires any assets or equity of any person engaged in Midstream Operations with a value in excess of $50 million (or $100 million in the aggregate with such party's other acquired Midstream Operations that have not been offered to the Midstream Partnership), the acquiring party will be required to offer the Midstream Partnership the opportunity to acquire such assets or equity for such value; provided, that the acquiring party will not be obligated to offer any such assets or equity to the Midstream Partnership if the acquiring party intends to cease using them in Midstream Operations within 12 months. If the Midstream Partnership does not exercise its option, then the acquiring party will be free to retain and operate such Midstream Operations; provided, however, that if the fair market value of such Midstream Operations is greater than 66 2/3 percent of the fair market value of all of the assets being acquired in such transaction, then the acquiring party will be required to dispose of such Midstream Operations within 24 months. As long as the ArcLight group has board observation rights, the ArcLight group will be prohibited from pursuing any transaction independently from the Midstream Partnership (i) if the ArcLight group's consent is required for the Midstream Partnership to pursue such transaction and (ii) the ArcLight group affirmatively votes not to consent to such transaction.

OGE Energy Midstream Partnership with CenterPoint Energy, Inc.

On March 14, 2013, OGE Energy entered into a Master Formation Agreement with the ArcLight group and CenterPoint Energy, Inc., pursuant to which OGE Energy, the ArcLight group and CenterPoint Energy, Inc., agreed to form the Midstream Partnership to own and operate the midstream businesses of OGE Energy and CenterPoint that will initially be structured as a private limited partnership. This transaction closed on May 1, 2013.

Pursuant to the Master Formation Agreement, OGE Energy and the ArcLight group indirectly contributed 100 percent of the equity interests in Enogex LLC to the Midstream Partnership. CenterPoint Energy Field Services, LLC, a Delaware limited liability company and wholly owned subsidiary of CenterPoint, was converted into a Delaware limited partnership that became the Midstream Partnership. CenterPoint contributed to the Midstream Partnership its equity interests in each of CenterPoint Energy Gas Transmission Company, LLC, a Delaware limited liability company, CenterPoint Energy - Mississippi River Transmission, LLC, a Delaware limited liability company, and certain of its other midstream subsidiaries and caused its subsidiary CenterPoint Energy Southeastern Pipelines Holding, LLC to contribute 49 percent of its interest in Southeast Supply Header, LLC, a Delaware limited liability company. CenterPoint Energy Field Services, LLC provides natural gas gathering and processing services for certain natural gas fields in the Mid-continent region of the United States that interconnect with CenterPoint Energy Gas Transmission Company, LLC and CenterPoint Energy - Mississippi River Transmission, LLC pipelines, as well as other interstate and intrastate pipelines. As of December 31, 2012, CenterPoint Energy Field Services, LLC gathered an average of approximately 2.5 billion cubic feet per day of natural gas. In addition, CenterPoint Energy Field Services, LLC has the capacity available to treat up to 2.5 billion cubic feet per day and process nearly 625 million cubic feet per day of natural gas. CenterPoint Energy Gas Transmission Company, LLC is an interstate pipeline that provides natural gas transportation, storage and pipeline services to customers principally in Arkansas, Louisiana, Oklahoma and Texas and includes the 1.9 billion cubic feet per day pipeline from Carthage, Texas to Perryville, Louisiana, which CenterPoint Energy Gas Transmission Company, LLC operates as a separate line with a fixed fuel rate. CenterPoint Energy - Mississippi River Transmission, LLC is an interstate pipeline that provides natural gas transportation, storage and pipeline services to customers principally in Arkansas, Illinois and Missouri. CenterPoint indirectly owns a 50 percent interest in Southeast Supply Header, LLC, which owns a 1.0 billion cubic feet per day, 274-mile interstate pipeline that runs from the Perryville Hub in Louisiana to Coden, Alabama. A wholly owned indirect subsidiary of Spectra Energy Corp. owns the remaining 50 percent interest in Southeast Supply Header, LLC. Upon closing, CenterPoint indirectly contributed 49 percent of its interest in the Southeast Supply Header, LLC to the Midstream Partnership. Upon receipt of certain consents, CenterPoint will contribute the remainder of its interest to the Midstream Partnership.

Immediately prior to closing, on May 1, 2013, the ArcLight group contributed $107.0 million and OGE Energy contributed $9.1 million to Enogex LLC in order to pay down short-term debt. At May 1, 2013, OGE Energy holds 28.5 percent of the limited partners interests, CenterPoint holds 58.3 percent of the limited partner interests and the ArcLight group holds 13.2 percent of the limited partner interests in the Midstream Partnership, provided, however, if CenterPoint obtains the approvals required to contribute its remaining indirect interest in Southeast Supply Header, LLC within 90 days after closing, CenterPoint will instead hold 59 percent of the limited partner interests, OGE would hold 28 percent of the limited partners interest and the ArcLight group would hold 13 percent of the limited partners interest.

After the expiration of the 90-day period after closing, CenterPoint has certain put rights, and the Midstream Partnership has certain call rights, exercisable with respect to any interest in Southeast Supply Header, LLC retained by CenterPoint following the formation of the Midstream Partnership, under which CenterPoint would contribute to the Midstream Partnership CenterPoint's retained interest in Southeast Supply Header, LLC at a price equal to the fair market value of such interest at the time the put right or call right is exercised. If CenterPoint were to exercise such put right or the Midstream Partnership were to exercise such call right, CenterPoint's retained interest in Southeast Supply Header, LLC would be contributed to the Midstream Partnership in exchange for consideration consisting of a specified number of limited partnership units and, subject to certain restrictions, a cash payment, payable either from CenterPoint to the Midstream Partnership or from the Midstream Partnership to CenterPoint, in an amount such that the total consideration exchanged is equal in value to the fair market value of the contributed interest in Southeast Supply Header, LLC.

The general partner of the Midstream Partnership is equally controlled by CenterPoint and OGE Energy, who each have 50 percent of the management rights. CenterPoint and OGE Energy also own a 40 percent and 60 percent interest, respectively, in any incentive distribution rights to be held by the general partner of the Midstream Partnership following an initial public offering of the Midstream Partnership. In addition, for a period of time, the ArcLight group will have board observation rights and approval rights over certain material activities of the Midstream Partnership, including material increases in capital expenditures and certain equity issuances, entering into transactions with related parties and acquiring, pledging or disposing of certain material assets. The general partner of the Midstream Partnership will initially be governed by a board made up of an equal number of representatives designated by each of CenterPoint Energy, Inc. and OGE Energy. Based on the 50/50 management ownership, with neither company having control, effective May 1, 2013, OGE Energy deconsolidated its interest in Enogex LLC and will account for its interest in the Midstream Partnership under the equity method of accounting.

Pursuant to a Registration Rights Agreement dated as of May 1, 2013, OGE Energy and CenterPoint Energy, Inc. agreed to initiate the process for the sale of an equity interest in the Midstream Partnership in an initial public offering. OGE Energy can give no assurances that the initial public offering will be consummated. Prior to consummating the initial public offering, OGE Energy, CenterPoint Energy, Inc. and the Midstream Partnership will need to complete the negotiation of the financial and other terms, including the initial public offering price. In addition, consummation of the initial public offering is subject to market conditions. For so long as the ArcLight group maintains a minimum ownership percentage, the ArcLight group is entitled to consult with the Midstream Partnership in connection with the initial public offering. The Midstream Partnership has agreed to file a registration statement for the initial public offering no later than May 1, 2014 and, subject to limited exceptions, consummate the initial public offering within 180 days of the filing of the registration statement.

In connection with the formation of the Midstream Partnership, on May 1, 2013, the Midstream Partnership entered into a $1.05 billion three-year senior unsecured term loan facility, the proceeds of which were used to repay $1.05 billion of intercompany indebtedness owed to CenterPoint. CenterPoint has guaranteed collection of the Midstream Partnership's obligations under the term loan, which guarantee is subordinated to all senior debt of CenterPoint. Effective May 1, 2013, the Midstream Partnership also entered into a $1.4 billion, five-year senior unsecured revolving credit facility in accordance with the terms of the Master Formation Agreement and Enogex LLC's $400 million revolving credit facility was terminated.

At March 31, 2013, Enogex LLC was obligated on approximately $700 million, in the aggregate, in indebtedness under its term loan, its revolving credit agreement and two series of its senior notes maturing in years 2014 and 2020. Certain of the entities contributed to the Midstream Partnership by CenterPoint are obligated on approximately $363 million of indebtedness owed to a wholly owned subsidiary of CenterPoint that is scheduled to mature in 2017.

Subject to the exceptions provided below, pursuant to the terms of an Omnibus Agreement dated as of May 1, 2013 among OGE Energy, the ArcLight group and CenterPoint Energy, Inc., each of OGE Energy and CenterPoint Energy, Inc. will be required to hold or otherwise conduct all of its respective Midstream Operations (as defined below) located within the United States in the Midstream Partnership. This restriction will cease to apply to both OGE Energy and CenterPoint Energy, Inc. as soon as either OGE Energy or CenterPoint Energy, Inc. ceases to hold (i) any interest in the general partner of the Midstream Partnership or (ii) at least 20 percent of the limited partner interests of the Midstream Partnership. "Midstream Operations" generally means, subject to certain exceptions, the gathering, compression, treatment, processing, blending, transportation, storage, isomerization and fractionation of crude oil and natural gas, its associated production water and enhanced recovery materials such as carbon dioxide, and its respective constituents and the following products: methane, NGLs (Y-grade, ethane, propane, normal butane, isobutane and natural gasoline), condensate, and refined products and distillates (gasoline, refined product blendstocks, olefins, naphtha, aviation fuels, diesel, heating oil, kerosene, jet fuels, fuel oil, residual fuel oil, heavy oil, bunker fuel, cokes, and asphalts), to the extent such activities are located within the United States.

In addition, if OGE Energy or CenterPoint Energy, Inc. acquires any assets or equity of any person engaged in Midstream Operations with a value in excess of $50 million (or $100 million in the aggregate with such party's other acquired Midstream Operations that have not been offered to the Midstream Partnership), the acquiring party will be required to offer the Midstream Partnership the opportunity to acquire such assets or equity for such value; provided, that the acquiring party will not be obligated to offer any such assets or equity to the Midstream Partnership if the acquiring party intends to cease using them in Midstream Operations within 12 months. If the Midstream Partnership does not exercise its option, then the acquiring party will be free to retain and operate such Midstream Operations; provided, however, that if the fair market value of such Midstream Operations is greater than 66 2/3 percent of the fair market value of all of the assets being acquired in such transaction, then the acquiring party will be required to dispose of such Midstream Operations within 24 months.

As long as the ArcLight group has board observation rights, the ArcLight group will be prohibited from pursuing any transaction independently from the Midstream Partnership (i) if the ArcLight group's consent is required for the Midstream Partnership to pursue such transaction and (ii) the ArcLight group affirmatively votes not to consent to such transaction.