Related Party Transactions	6 Months Ended
Jun. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Services Agreement and Transition Services Agreement with GenOn The Company provides GenOn with various management, personnel and other services, which include human resources, regulatory and public affairs, accounting, tax, legal, information systems, treasury, risk management, commercial operations, and asset management, as set forth in the services agreement with GenOn, or the Services Agreement. The initial term of the Services Agreement was through December 31, 2013, with an automatic renewal absent a request for termination. The fee charged was determined based on a fixed amount as described in the Services Agreement and was calculated based on historical GenOn expenses prior to the NRG Merger. The annual fees under the Services Agreement were approximately $193 million and management has concluded that this method of charging overhead costs is reasonable. As described in Note 3, Acquisitions, Discontinued Operations and Dispositions, in connection with the Restructuring Support Agreement, NRG agreed to provide shared services to GenOn under the Services Agreement for an adjusted annualized fee of $84 million. In December 2017, in conjunction with the confirmation of the GenOn Entities' plan of reorganization, the Services Agreement was terminated and replaced by the transition services agreement. Under the transition services agreement, NRG provided the shared services and other separation services at an annualized rate of $84 million, subject to certain credits and adjustments. GenOn provided notice to NRG of its intent to terminate the transition services agreement effective August 15, 2018 and in connection with the settlement agreement described in Note 3, Acquisitions, Discontinued Operations and Dispositions, all amounts owed and payable to NRG were settled against the $28 million credit provided for in the Restructuring Support Agreement. NRG may provide additional separation services that are necessary for or reasonably related to the operation of GenOn's business after such date, subject to NRG's prior written consent, not to be unreasonably withheld. For the three and six months ended June 30, 2018, NRG recorded approximately $21 million and $42 million, respectively, under the transition services agreement against selling, general and administrative expenses post-Chapter 11 Filing. For the three and six months ended June 30, 2017, NRG recorded other income - affiliate related to these services of $39 million and $87 million, respectively. Credit Agreement with GenOn NRG and GenOn are party to a secured intercompany revolving credit agreement. The intercompany revolving credit agreement provided for a $500 million revolving credit facility, all of which was available for revolving loans and letters of credit. At June 30, 2018 and December 31, 2017, $45 million and $92 million, respectively, of letters of credit were issued and outstanding under the NRG credit agreement for GenOn. Additionally, as of June 30, 2018 and December 31, 2017, there were $151 million and $125 million, respectively, of loans outstanding under the intercompany secured revolving credit facility. In addition, the intercompany secured revolving credit facility contains customary covenants and events of default. As of June 30, 2018, GenOn was in default under the secured intercompany revolving credit agreement due to the filing of the Chapter 11 Cases. As a result of the Chapter 11 Cases, no additional revolving loans or letters of credit are available to GenOn. As the Restructuring Support Agreement provided that the borrowings be repaid to NRG at or prior to emergence, NRG recorded its affiliate receivable for the amount outstanding net within accrued expenses and other current liabilities - affiliate on the consolidated balance sheet as of June 30, 2018. Interest continued to accrue during the pendency of the Chapter 11 Cases until July 2018, when all borrowings and related interest were settled against amounts owed by the Company to GenOn as further discussed in Note 3 , Acquisitions, Discontinued Operations and Dispositions, in connection with the settlement between NRG and GenOn. Commercial Operations Agreement NRG Power Marketing LLC has entered into physical and financial intercompany commodity and hedging transactions with GenOn and certain of its subsidiaries. Subject to applicable collateral thresholds, these arrangements may provide for the bilateral exchange of credit support based upon market exposure and potential market movements. The terms and conditions of the agreements are generally consistent with industry practices and other third party arrangements. As of June 30, 2018, derivative assets and liabilities associated with these transactions are recorded within NRG's derivative instruments balances on the consolidated balance sheet, with related revenues and costs within operating revenues and cost of operations, respectively. Additionally, as of June 30, 2018 and December 31, 2017, the Company had $24 million and $32 million, respectively, of cash collateral posted in support of energy risk management activities by GenOn.

Related Party Transactions

Services Agreement and Transition Services Agreement with GenOn

The Company provides GenOn with various management, personnel and other services, which include human resources, regulatory and public affairs, accounting, tax, legal, information systems, treasury, risk management, commercial operations, and asset management, as set forth in the services agreement with GenOn, or the Services Agreement. The initial term of the Services Agreement was through December 31, 2013, with an automatic renewal absent a request for termination. The fee charged was determined based on a fixed amount as described in the Services Agreement and was calculated based on historical GenOn expenses prior to the NRG Merger. The annual fees under the Services Agreement were approximately $193 million and management has concluded that this method of charging overhead costs is reasonable. As described in Note 3, Acquisitions, Discontinued Operations and Dispositions, in connection with the Restructuring Support Agreement, NRG agreed to provide shared services to GenOn under the Services Agreement for an adjusted annualized fee of $84 million.

In December 2017, in conjunction with the confirmation of the GenOn Entities' plan of reorganization, the Services Agreement was terminated and replaced by the transition services agreement. Under the transition services agreement, NRG provided the shared services and other separation services at an annualized rate of $84 million, subject to certain credits and adjustments. GenOn provided notice to NRG of its intent to terminate the transition services agreement effective August 15, 2018 and in connection with the settlement agreement described in Note 3, Acquisitions, Discontinued Operations and Dispositions, all amounts owed and payable to NRG were settled against the $28 million credit provided for in the Restructuring Support Agreement. NRG may provide additional separation services that are necessary for or reasonably related to the operation of GenOn's business after such date, subject to NRG's prior written consent, not to be unreasonably withheld. For the three and six months ended June 30, 2018, NRG recorded approximately $21 million and $42 million, respectively, under the transition services agreement against selling, general and administrative expenses post-Chapter 11 Filing. For the three and six months ended June 30, 2017, NRG recorded other income - affiliate related to these services of $39 million and $87 million, respectively.

Credit Agreement with GenOn

NRG and GenOn are party to a secured intercompany revolving credit agreement. The intercompany revolving credit agreement provided for a $500 million revolving credit facility, all of which was available for revolving loans and letters of credit. At June 30, 2018 and December 31, 2017, $45 million and $92 million, respectively, of letters of credit were issued and outstanding under the NRG credit agreement for GenOn. Additionally, as of June 30, 2018 and December 31, 2017, there were $151 million and $125 million, respectively, of loans outstanding under the intercompany secured revolving credit facility. In addition, the intercompany secured revolving credit facility contains customary covenants and events of default. As of June 30, 2018, GenOn was in default under the secured intercompany revolving credit agreement due to the filing of the Chapter 11 Cases.

As a result of the Chapter 11 Cases, no additional revolving loans or letters of credit are available to GenOn. As the Restructuring Support Agreement provided that the borrowings be repaid to NRG at or prior to emergence, NRG recorded its affiliate receivable for the amount outstanding net within accrued expenses and other current liabilities - affiliate on the consolidated balance sheet as of June 30, 2018. Interest continued to accrue during the pendency of the Chapter 11 Cases until July 2018, when all borrowings and related interest were settled against amounts owed by the Company to GenOn as further discussed in Note 3 , Acquisitions, Discontinued Operations and Dispositions, in connection with the settlement between NRG and GenOn.

Commercial Operations Agreement

NRG Power Marketing LLC has entered into physical and financial intercompany commodity and hedging transactions with GenOn and certain of its subsidiaries. Subject to applicable collateral thresholds, these arrangements may provide for the bilateral exchange of credit support based upon market exposure and potential market movements. The terms and conditions of the agreements are generally consistent with industry practices and other third party arrangements. As of June 30, 2018, derivative assets and liabilities associated with these transactions are recorded within NRG's derivative instruments balances on the consolidated balance sheet, with related revenues and costs within operating revenues and cost of operations, respectively. Additionally, as of June 30, 2018 and December 31, 2017, the Company had $24 million and $32 million, respectively, of cash collateral posted in support of energy risk management activities by GenOn.