Business Acquisitions and Dispositions	9 Months Ended
Sep. 30, 2012
Business Acquisitions and Dispositions [Abstract]
Acquisitions and Dispositions [Text Block]	Business Acquisitions and Dispositions Pending Acquisition On July 20, 2012, the Company entered into an agreement, or the Merger Agreement, to acquire GenOn Energy, Inc., or GenOn. GenOn, a generator of wholesale electricity, has baseload, intermediate and peaking power generation facilities using coal, natural gas and oil, totaling approximately 22,700 MW. The Company will issue, as consideration for the acquisition, 0.1216 shares of NRG common stock for each outstanding share of GenOn, including restricted stock units outstanding, on the acquisition date, except for fractional shares which will be paid in cash. Based upon total GenOn shares outstanding as of September 30, 2012, the Company expects to issue approximately 94 million shares of NRG common stock, or 29% of total common shares outstanding following the close of the transaction. NRG and GenOn will hold their respective special meetings of stockholders on November 9, 2012. The stockholders who held shares of NRG and GenOn on Friday, October 5, 2012, will be entitled to vote at their respective special meeting on the proposals pertaining to the merger of the companies. On September 21, 2012, the Department of Justice and the Federal Trade Commission granted early termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended. On October 25, 2012, the Public Utility Commission of Texas, or PUCT, approved the merger. Additionally, the 90-day prior notice period to the California Public Utilities Commission, or CPUC, required under California law expired on October 31, 2012. The merger remains subject to the satisfaction or waiver of other closing conditions, including approval by the stockholders of both companies and regulatory approvals by the Federal Energy Regulatory Commission, or the FERC, and the New York Public Service Commission, or NYPSC. Additionally, the companies have requested a threshold determination by the U.S. Nuclear Regulatory Commission, or the NRC, that its approval is not required. The acquisition is expected to close by the first quarter of 2013. 2012 Dispositions Agua Caliente On January 18, 2012, the Company completed the sale of a 49% interest in NRG Solar AC Holdings LLC, the indirect owner of the Agua Caliente project, to MidAmerican Energy Holdings Company, or MidAmerican. A majority of the $122 million of cash consideration received at closing represented 49% of construction costs funded by NRG's equity contributions. The excess of the consideration over the carrying value of the divested interest was recorded to additional paid-in capital. MidAmerican will fund its proportionate share of future equity contributions and other credit support for the project. NRG continues to hold a majority interest in and consolidate the project. Saale Energie GmbH On July 17, 2012, the Company completed the sale of its 100% interest in Saale Energie GmbH, which holds a 41.9% interest in Kraftwerke Schkopau GbR and a 44.4% interest in Kraftwerke Schkopau Betriebsgesllschaft mbH, collectively, Schkopau. Schkopau holds a fixed 400 MW participation in the 900 MW Schkopau Power Station located in Germany. In connection with the sale of Schkopau, NRG entered into a foreign currency swap contract to hedge the impact of exchange rate fluctuations on the sale proceeds of €141 million. The Company received cash consideration, net of selling expenses, of $174 million, which included $4 million related to the settlement of the swap contract that was recorded as a gain within Other income, net in the quarter ended September 30, 2012. The cash consideration approximated the book value of the net assets, including cash of $38 million, on the date of the sale. 2011 Acquisitions The Company's acquisitions that are considered business combinations are accounted for under the acquisition method of accounting in accordance with ASC 805, Business Combinations, or ASC 805, with identifiable assets acquired and liabilities assumed provisionally recorded at their estimated fair values on the acquisition date. The provisional amounts recognized are subject to revision until the evaluations are completed and to the extent that additional information is obtained about the facts and circumstances that existed as of the acquisition date, are required to be finalized within a measurement period not to exceed one year. The Company made several acquisitions in 2011, which were recorded as business combinations under ASC 805, for which the accounting was not finalized as of December 31, 2011. See Note 3, Business Acquisitions and Dispositions and Note 12, Debt and Capital Leases, in the Company's 2011 Form 10-K, for additional information related to these acquisitions. The accounting for the acquisitions of Energy Plus, California Valley Solar Ranch, or CVSR, Agua Caliente and Ivanpah were completed as of March 31, 2012, at which point the provisional fair values became final with no material changes.

Business Acquisitions and Dispositions

Pending Acquisition

On July 20, 2012, the Company entered into an agreement, or the Merger Agreement, to acquire GenOn Energy, Inc., or GenOn. GenOn, a generator of wholesale electricity, has baseload, intermediate and peaking power generation facilities using coal, natural gas and oil, totaling approximately 22,700 MW. The Company will issue, as consideration for the acquisition, 0.1216 shares of NRG common stock for each outstanding share of GenOn, including restricted stock units outstanding, on the acquisition date, except for fractional shares which will be paid in cash. Based upon total GenOn shares outstanding as of September 30, 2012, the Company expects to issue approximately 94 million shares of NRG common stock, or 29% of total common shares outstanding following the close of the transaction.

NRG and GenOn will hold their respective special meetings of stockholders on November 9, 2012. The stockholders who held shares of NRG and GenOn on Friday, October 5, 2012, will be entitled to vote at their respective special meeting on the proposals pertaining to the merger of the companies.

On September 21, 2012, the Department of Justice and the Federal Trade Commission granted early termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended. On October 25, 2012, the Public Utility Commission of Texas, or PUCT, approved the merger. Additionally, the 90-day prior notice period to the California Public Utilities Commission, or CPUC, required under California law expired on October 31, 2012.

The merger remains subject to the satisfaction or waiver of other closing conditions, including approval by the stockholders of both companies and regulatory approvals by the Federal Energy Regulatory Commission, or the FERC, and the New York Public Service Commission, or NYPSC. Additionally, the companies have requested a threshold determination by the U.S. Nuclear Regulatory Commission, or the NRC, that its approval is not required. The acquisition is expected to close by the first quarter of 2013.

2012 Dispositions

Agua Caliente

On January 18, 2012, the Company completed the sale of a 49% interest in NRG Solar AC Holdings LLC, the indirect owner of the Agua Caliente project, to MidAmerican Energy Holdings Company, or MidAmerican. A majority of the $122 million of cash consideration received at closing represented 49% of construction costs funded by NRG's equity contributions. The excess of the consideration over the carrying value of the divested interest was recorded to additional paid-in capital. MidAmerican will fund its proportionate share of future equity contributions and other credit support for the project. NRG continues to hold a majority interest in and consolidate the project.

Saale Energie GmbH

On July 17, 2012, the Company completed the sale of its 100% interest in Saale Energie GmbH, which holds a 41.9% interest in Kraftwerke Schkopau GbR and a 44.4% interest in Kraftwerke Schkopau Betriebsgesllschaft mbH, collectively, Schkopau. Schkopau holds a fixed 400 MW participation in the 900 MW Schkopau Power Station located in Germany. In connection with the sale of Schkopau, NRG entered into a foreign currency swap contract to hedge the impact of exchange rate fluctuations on the sale proceeds of €141 million. The Company received cash consideration, net of selling expenses, of $174 million, which included $4 million related to the settlement of the swap contract that was recorded as a gain within Other income, net in the quarter ended September 30, 2012. The cash consideration approximated the book value of the net assets, including cash of $38 million, on the date of the sale.

2011 Acquisitions

The Company's acquisitions that are considered business combinations are accounted for under the acquisition method of accounting in accordance with ASC 805, Business Combinations, or ASC 805, with identifiable assets acquired and liabilities assumed provisionally recorded at their estimated fair values on the acquisition date. The provisional amounts recognized are subject to revision until the evaluations are completed and to the extent that additional information is obtained about the facts and circumstances that existed as of the acquisition date, are required to be finalized within a measurement period not to exceed one year. The Company made several acquisitions in 2011, which were recorded as business combinations under ASC 805, for which the accounting was not finalized as of December 31, 2011. See Note 3, Business Acquisitions and Dispositions and Note 12, Debt and Capital Leases, in the Company's 2011 Form 10-K, for additional information related to these acquisitions.

The accounting for the acquisitions of Energy Plus, California Valley Solar Ranch, or CVSR, Agua Caliente and Ivanpah were completed as of March 31, 2012, at which point the provisional fair values became final with no material changes.