NRG Energy (NRG) 10-Q 8 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2018shares
Document And Entity Information [Abstract]
Entity Registrant Name	NRG ENERGY, INC.
Entity Central Index Key	1,013,871
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding	289,930,024
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Revenues
Total operating revenues	$ 3,061	$ 2,740	$ 7,795	$ 7,246
Operating Costs and Expenses
Cost of operations	2,307	2,072	5,730	5,589
Depreciation and amortization	112	163	370	490
Impairment losses	0	0	74	60
Selling, general and administrative	212	190	591	634
Reorganization costs	27	12	70	18
Development costs	1	6	9	18
Total operating costs and expenses	2,659	2,443	6,844	6,809
Other income - affiliate	0	0	0	87
Gain on sale of assets	14	0	30	4
Operating Income/(Loss)	416	297	981	528
Other Income/(Expense)
Equity in earnings/(losses) of unconsolidated affiliates	20	9	26	(20)
Other income/(expense), net	17	19	(4)	43
Loss on debt extinguishment, net	(19)	0	(22)	0
Interest expense	(121)	(139)	(361)	(432)
Total other income/(expense)	(103)	(111)	(361)	(409)
Income from Continuing Operations Before Income Taxes	313	186	620	119
Income tax expense/(benefit)	7	1	19	3
Income from Continuing Operations	306	185	601	116
Income/(Loss) from discontinued operations, net of income tax	(354)	(22)	(320)	(798)
Net (Loss)/Income	(48)	163	281	(682)
Less: Net income/(loss) attributable to noncontrolling interest and redeemable noncontrolling interests	24	(8)	1	(63)
Net (Loss)/Income Attributable to NRG Energy, Inc. common stockholders	$ (72)	$ 171	$ 280	$ (619)
(Loss)/Earnings per Share Attributable to NRG Energy, Inc. Common Stockholders
Weighted average number of common shares outstanding — basic (in shares)	299	317	309	317
Income from continuing operations per weighted average common share — basic (in usd per share)	$ 0.94	$ 0.61	$ 1.94	$ 0.56
Loss from discontinued operations per weighted average common share — basic (in usd per share)	(1.18)	(0.07)	(1.03)	(2.51)
(Loss)/Earnings per Weighted Average Common Share — Basic (in usd per share)	$ (0.24)	$ 0.54	$ 0.91	$ (1.95)
Weighted average number of common shares outstanding — diluted (in shares)	299	322	313	317
Income from continuing operations per weighted average common share — diluted (in usd per share)	$ 0.94	$ 0.60	$ 1.91	$ 0.56
Loss from discontinued operations per weighted average common share — diluted (in usd per share)	(1.18)	(0.07)	(1.02)	(2.51)
(Loss)/Earnings per Weighted Average Common Share — Diluted (in usd per share)	(0.24)	0.53	0.89	(1.95)
Dividends Per Common Share (in usd per share)	$ 0.03	$ 0.03	$ 0.09	$ 0.09

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive (Loss)/Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net (loss)/income	$ (48)	$ 163	$ 281	$ (682)
Other comprehensive income/(loss), net of tax
Unrealized gain on derivatives, net of income tax expense of $0, $0, $1, and $0	4	7	24	7
Foreign currency translation adjustments, net of income tax expense of $0, $0, $0, and $0	(2)	2	(8)	9
Available-for-sale securities, net of income tax expense of $0, $0, $0, and $0	0	1	1	2
Defined benefit plans, net of income tax expense of $0, $0, $0, and $0	(1)	(1)	(3)	25
Other comprehensive income	1	9	14	43
Comprehensive (loss) income	(47)	172	295	(639)
Less: Comprehensive income/(loss) attributable to noncontrolling interest and redeemable noncontrolling interest	26	(5)	15	(61)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	$ (73)	$ 177	$ 280	$ (578)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive (Loss)/Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gain/(loss) on derivatives, income tax expense	$ 0	$ 0	$ 1	$ 0
Foreign currency translation adjustments, income tax expense	0	0	0	0
Available-for-sale securities,income tax expense	0	0	0	0
Defined benefit plans, income tax expense	$ 0	$ 0	$ 0	$ 0

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 1,359	$ 767
Funds deposited by counterparties	30	37
Restricted cash	28	279
Accounts receivable, net	1,297	960
Inventory	408	486
Derivative instruments	683	624
Cash collateral paid in support of energy risk management activities	209	171
Accounts receivable - affiliate	19	186
Prepayments and other current assets	248	179
Current assets - held for sale	0	116
Current assets - discontinued operations	4	705
Total current assets	4,285	4,510
Property, plant and equipment, net	3,599	6,435
Other Assets
Equity investments in affiliates	452	182
Notes receivable, less current portion	10	2
Goodwill	539	539
Intangible assets, net	602	507
Nuclear decommissioning trust fund	719	692
Derivative instruments	392	159
Deferred income taxes	11	6
Other non-current assets	281	294
Non-current assets held-for-sale	0	43
Non-current assets - discontinued operations	560	10,181
Total other assets	3,566	12,605
Total Assets	11,450	23,550
Current Liabilities
Current portion of long-term debt and capital leases	593	204
Accounts payable	824	711
Accounts payable - affiliate	14	57
Derivative instruments	550	537
Cash collateral received in support of energy risk management activities	30	37
Accrued expenses and other current liabilities	659	769
Accrued expenses and other current liabilities - affiliate	1	161
Current liabilities - held-for-sale	0	72
Current liabilities - discontinued operations	52	864
Total current liabilities	2,723	3,412
Non-Current Liabilities
Long-term debt and capital leases	6,658	9,180
Nuclear decommissioning reserve	278	269
Nuclear decommissioning trust liability	432	415
Deferred income taxes	18	21
Derivative instruments	357	143
Out-of-market contracts, net	177	195
Other non-current liabilities	1,177	1,002
Non-current liabilities - held-for-sale	0	8
Non-current liabilities - discontinued operations	547	6,859
Total non-current liabilities	9,644	18,092
Total Liabilities	12,367	21,504
Redeemable noncontrolling interest in subsidiaries	19	78
Commitments and Contingencies
Stockholders’ Equity
Common stock	4	4
Additional paid-in capital	8,453	8,377
Accumulated deficit	(6,001)	(6,269)
Less treasury stock, at cost - 129,948,876 and 101,580,045 shares, at September 30, 2018 and December 31, 2017, respectively	(3,334)	(2,386)
Accumulated other comprehensive loss	(58)	(72)
Noncontrolling interest	0	2,314
Total Stockholders’ Equity	(936)	1,968
Total Liabilities and Stockholders’ Equity	$ 11,450	$ 23,550

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Treasury stock, shares (in shares)	129,948,876	101,580,045

Condensed Consolidated Statem_4

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities
Net (loss)/income	$ 281	$ (682)
Income/(Loss) from discontinued operations, net of income tax	(320)	(798)
Income from Continuing Operations	601	116
Adjustments to reconcile net income to net cash provided by operating activities:
Distributions and equity in earnings of unconsolidated affiliates	10	0
Depreciation, amortization and accretion	403	490
Provision for bad debts	57	57
Amortization of nuclear fuel	38	37
Amortization of financing costs and debt discount/premiums	21	15
Adjustment for debt extinguishment	22	3
Amortization of intangibles and out-of-market contracts	21	79
Amortization of unearned equity compensation	36	27
Impairment losses	89	60
Changes in deferred income taxes and liability for uncertain tax benefits	(6)	(1)
Changes in nuclear decommissioning trust liability	50	20
Changes in derivative instruments	(17)	36
Changes in collateral deposits in support of energy risk management activities	(30)	(103)
Gain on sale of emission allowances	(20)	21
Gain on sale of assets	(30)	(4)
GenOn settlement in July 2018	(125)	0
Loss on deconsolidation of business	13	0
Changes in other working capital	(375)	(295)
Cash provided/(used) by continuing operations	758	558
Cash provided by discontinued operations	324	178
Net Cash Provided/(Used) by Operating Activities	1,082	736
Cash Flows from Investing Activities
Acquisitions of businesses, net of cash acquired	(209)	(12)
Capital expenditures	(345)	(172)
Purchases of emission allowances	(30)	(47)
Proceeds from sale of emission allowances	54	104
Investments in nuclear decommissioning trust fund securities	(449)	(402)
Proceeds from the sale of nuclear decommissioning trust fund securities	398	382
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees	1,555	309
Deconsolidation of business	(268)	0
Changes in investments in unconsolidated affiliates	(62)	24
Other	0	30
Cash (used)/provided by continuing operations	644	216
Cash used by discontinued operations	(703)	(638)
Net Cash (Used)/Provided by Investing Activities	(59)	(422)
Cash Flows from Financing Activities
Payment of dividends to common stockholders	(28)	(28)
Payment for treasury stock	(1,000)	0
Proceeds from issuance of long-term debt	995	308
Payments for short and long-term debt	(970)	(343)
Receivable from affiliate	(26)	(125)
Net distributions to noncontrolling interests from subsidiaries	(17)	(18)
Payment of debt issuance costs	(19)	(39)
Other	(4)	(8)
Cash provided/(used) by continuing operations	(1,069)	(253)
Cash provided by discontinued operations	403	39
Net Cash Provided/(Used) by Financing Activities	(666)	(214)
Effect of exchange rate changes on cash and cash equivalents	1	(10)
Change in Cash from discontinued operations	24	(421)
Net Increase in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash	334	511
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period	1,083	860
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	$ 1,417	$ 1,371

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation General NRG Energy, Inc., or NRG or the Company, is a customer-driven integrated power company built on a portfolio of dynamic retail electricity brands and diverse generation assets. NRG is continuously focused on serving the energy needs of end-use residential, commercial and industrial customers in competitive markets through multiple brands and channels. The Company: • directly sells energy and innovative, sustainable products and services to retail customers under the names “NRG”, “Reliant” and other retail brand names owned by NRG; • owns approximately 26,000 MW of generation; • engages in the trading of wholesale energy, capacity and related products; and • transacts in and trades fuel and transportation services. The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with the SEC's regulations for interim financial information and with the instructions to Form 10-Q. Accordingly, they do not include all of the information and notes required by generally accepted accounting principles for complete financial statements. The following notes should be read in conjunction with the accounting policies and other disclosures as set forth in the notes to the consolidated financial statements in the Company's 2017 Form 10-K. Interim results are not necessarily indicative of results for a full year. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements contain all material adjustments consisting of normal and recurring accruals necessary to present fairly the Company's consolidated financial position as of September 30, 2018 , and the results of operations, comprehensive income/(loss) and cash flows for the three and nine months ended September 30, 2018 and 2017 . Discontinued Operations On August 31, 2018, as described in Note 3 , Acquisitions, Discontinued Operations and Dispositions , NRG deconsolidated NRG Yield, Inc. and its Renewables Platform for financial reporting purposes. The financial information for all historical periods has been recast to reflect the presentation of these entities, as well as the Carlsbad project, as discontinued operations. As a result of the sale of NRG Yield, the Company no longer controls the Agua Caliente project. Due to this change in control, the Company has also deconsolidated the Agua Caliente project from its financial results and has accounted for the project as an equity method investment. GenOn Chapter 11 Cases On June 14, 2017, GenOn, along with GenOn Americas Generation and certain of their directly and indirectly-owned subsidiaries, or collectively the GenOn Entities, filed voluntary petitions for relief under Chapter 11, or the Chapter 11 Cases, of the U.S. Bankruptcy Code, in the U.S. Bankruptcy Court for the Southern District of Texas, Houston Division, or the Bankruptcy Court. GenOn Mid-Atlantic, as well as its consolidated subsidiaries, REMA and certain other subsidiaries, did not file for relief under Chapter 11. As a result of the bankruptcy filings and beginning on June 14, 2017, GenOn and its subsidiaries were deconsolidated from NRG’s consolidated financial statements. NRG determined that this disposal of GenOn and its subsidiaries is a discontinued operation and, accordingly, the financial information for all historical periods has been recast to reflect GenOn as a discontinued operation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates. Reclassifications Certain prior year amounts have been reclassified for comparative purposes. The reclassifications did not affect results from operations, net assets or cash flows.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Other Balance Sheet Information The following table presents the allowance for doubtful accounts included in accounts receivable, net; accumulated depreciation included in property, plant and equipment, net; accumulated amortization included in intangible assets, net and accumulated amortization included in out-of-market contracts, net: September 30, 2018 December 31, 2017 (In millions) Accounts receivable allowance for doubtful accounts $ 37 $ 28 Property, plant and equipment accumulated depreciation 2,652 3,013 Intangible assets accumulated amortization 1,194 1,572 Out-of-market contracts accumulated amortization 372 354 Restricted Cash The following table provides a reconciliation of cash and cash equivalents, restricted cash and funds deposited by counterparties reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the statement of cash flows. September 30, 2018 December 31, 2017 September 30, 2017 December 31, 2016 (In millions) Cash and cash equivalents $ 1,359 $ 767 $ 1,022 $ 591 Funds deposited by counterparties 30 37 31 2 Restricted cash 28 279 318 267 Cash and cash equivalents, funds deposited by counterparties and restricted cash shown in the statement of cash flows $ 1,417 $ 1,083 $ 1,371 $ 860 Funds deposited by counterparties consist of cash held by the Company as a result of collateral posting obligations from its counterparties. Some amounts are segregated into separate accounts that are not contractually restricted but, based on the Company's intention, are not available for the payment of general corporate obligations. Depending on market fluctuations and the settlement of the underlying contracts, the Company will refund this collateral to the hedge counterparties pursuant to the terms and conditions of the underlying trades. Since collateral requirements fluctuate daily and the Company cannot predict if any collateral will be held for more than twelve months, the funds deposited by counterparties are classified as a current asset on the Company's balance sheet, with an offsetting liability for this cash collateral received within current liabilities. Restricted cash consists primarily of funds held to satisfy the requirements of certain debt agreements and funds held within the Company's projects that are restricted in their use. Pension and Post Retirement Benefit Plan Amendments In the fourth quarter of 2018, the Company will recognize a loss of $17 million related to curtailment of certain of the Company's pension plan. The Company also amended the post retirement benefit plan and, as a result of the subsequent plan remeasurement, will recognize a gain of $2 million . Noncontrolling Interest The following table reflects the changes in NRG's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 2,314 Dividends paid to NRG Yield, Inc. public shareholders (61 ) Distributions to noncontrolling interest (43 ) Net income attributable to noncontrolling interest - continuing operations 5 Net income attributable to noncontrolling interest - discontinued operations 21 Other comprehensive income attributable to noncontrolling interest - discontinued operations 14 Non-cash adjustments to noncontrolling interest 10 Contributions from noncontrolling interest 296 Sale of assets to NRG Yield, Inc. (8 ) Deconsolidation of Ivanpah (a) (89 ) Deconsolidation of Agua Caliente (b) (279 ) Deconsolidation of NRG Yield and the Renewables Platform (b) (2,180 ) Balance as of September 30, 2018 $ — (a) See Note 9 , Variable Interest Entities, or VIEs for further information regarding the deconsolidation of Ivanpah effective April 2018. (b) See Note 3 , Acquisitions, Discontinued Operations and Dispositions for further information regarding the sale of NRG Yield and the Renewables Platform and the deconsolidation of Agua Caliente. Redeemable Noncontrolling Interest The following table reflects the changes in the Company's redeemable noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 78 Distributions to redeemable noncontrolling interest (3 ) Contributions from redeemable noncontrolling interest 26 Non-cash adjustments to redeemable noncontrolling interest (9 ) Net income attributable to redeemable noncontrolling interest - continuing operations 1 Net income attributable to redeemable noncontrolling interest - discontinued operations (26 ) Deconsolidation of NRG Yield and the Renewables Platform (a) (48 ) Balance as of September 30, 2018 $ 19 (a) See Note 3 , Acquisitions, Discontinued Operations and Dispositions for further information regarding the sale of NRG Yield and the Renewables Platform. Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606 using the modified retrospective method applied to contracts that were not completed as of the adoption date. The Company recognized the cumulative effect of initially applying the new standard as a credit to the opening balance of accumulated deficit, resulting in a decrease of approximately $16 million . The adjustment primarily related to costs incurred to obtain a contract with customers and customer incentives. Following the adoption of the new standard, the Company’s revenue recognition of its contracts with customers remains materially consistent with its historical practice. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company's policies with respect to its various revenue streams are detailed below. In general, the Company applies the invoicing practical expedient to recognize revenue for the revenue streams detailed below, except in circumstances where the invoiced amount does not represent the value transferred to the customer. Retail Revenues Gross revenues for energy sales and services to retail customers are recognized as the Company transfers the promised goods and services to the customer. For the majority of its electricity contracts, the Company’s performance obligation with the customer is satisfied over time and performance obligations for its electricity products are recognized as the customer takes possession of the product. The Company also allocates the contract consideration to distinct performance obligation in a contract for which the timing of the revenue recognized is different. Additionally, customer discounts and incentives reduce the contract consideration and are recognized over the term of the contract. Energy sales and services that have been delivered but not billed by period end are estimated. Accrued unbilled revenues are based on estimates of customer usage since the date of the last meter reading provided by the independent system operators or electric distribution companies. Volume estimates are based on daily forecasted volumes and estimated customer usage by class. Unbilled revenues are calculated by multiplying these volume estimates by the applicable rate by customer class. Estimated amounts are adjusted when actual usage is known and billed. As contracts for retail electricity can be for multi-year periods, the Company has performance obligations under these contracts that have not yet been satisfied. These performance obligations have transaction prices that are both fixed and variable, and that vary based on the contract duration, customer type, inception date and other contract-specific factors. For the fixed price contracts, the amount of any unsatisfied performance obligations will vary based on customer usage, which will depend on factors such as weather and customer activity and therefore it is not practicable to estimate such amounts. Energy Revenue Both physical and financial transactions are entered into to optimize the financial performance of the Company's generating facilities. Electric energy revenue is recognized upon transmission to the customer over time, using the output method for measuring progress of satisfaction of performance obligations. Physical transactions, or the sale of generated electricity to meet supply and demand, are recorded on a gross basis in the Company's consolidated statements of operations. The Company applies the invoicing practical expedient, where applicable, in recognizing energy revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Financial transactions, or the buying and selling of energy for trading purposes, are recorded net within operating revenues in the consolidated statements of operations in accordance with ASC 815. Capacity Revenue Capacity revenues consist of revenues billed to a third party at either the market or a negotiated contract price for making installed generation and demand response capacity available in order to satisfy system integrity and reliability requirements. Capacity revenues are recognized over time, using the output method for measuring progress of satisfaction of performance obligations. The Company applies the invoicing practical expedient, where applicable, in recognizing capacity revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Capacity revenue contracts mainly consist of: Capacity auctions — The Company's largest sources of capacity revenues are capacity auctions in PJM, ISO-NE, and NYISO. Both ISO-NE and PJM operate a pay-for-performance model where capacity payments are modified based on real-time performance, where NRG's actual revenues will be the combination of revenues based on the cleared auction MWs plus the net of any over- and under-performance of NRG's fleet. In addition, MISO has an annual auction, known as the Planning Resource Auction, or PRA. The Gulf Coast assets situated in the MISO market may participate in this auction. Estimated future revenues for cleared auction MWs in the various capacity auctions are $152 million , $610 million , $459 million , $528 million and $244 million for fiscal years 2018 , 2019 , 2020 , 2021 and 2022 , respectively. Resource adequacy and bilateral contracts — In California, there is a resource adequacy requirement that is primarily satisfied through bilateral contracts. Such bilateral contracts are typically short-term resource adequacy contracts. When bilateral contracting does not satisfy the resource adequacy need, such shortfalls can be addressed through procurement tools administered by the CAISO, including the capacity procurement mechanism or reliability must-run contracts. Demand payments from the current long-term contracts are tied to summer peak demand and provide a mechanism for recovering a portion of the costs associated with new or changed environmental laws or regulations. In Texas, capacity and contracted revenues are through bilateral contracts with load serving entities. Renewable Energy Credits As stated above, renewable energy credits are usually sold through long-term PPAs. Revenue from the sale of self-generated RECs is recognized when related energy is generated and simultaneously delivered even in cases where there is a certification lag as it has been deemed to be perfunctory. In a bundled contract to sell energy, capacity and/or self-generated RECs, all performance obligations are deemed to be delivered at the same time and hence, timing of recognition of revenue for all performance obligations is the same and occurs over time. In such cases, it is often unnecessary to allocate transaction price to multiple performance obligations. Sale of Emission Allowances The Company records its inventory of emission allowances as part of intangible assets. From time to time, management may authorize the transfer of emission allowances in excess of expected usage from the Company's emission bank to intangible assets held-for-sale for trading purposes. The Company records the sale of emission allowances on a net basis within operating revenue in the Company's consolidated statements of operations. Disaggregated Revenues The following table represents the Company’s disaggregation of revenue from contracts with customers for the three and nine months ended September 30, 2018 , along with the reportable segment for each category: Three months ended September 30, 2018 Generation (In millions) Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue (a) $ — $ 680 $ 278 $ 958 $ (479 ) $ 479 Capacity revenue (a) — 66 187 253 1 254 Retail revenue Mass customers 1,768 — — — (2 ) 1,766 Business Solutions customers 434 — — — — 434 Total retail revenue 2,202 — — — (2 ) 2,200 Mark-to-market for economic hedging activities (b) 1 268 27 295 (241 ) 55 Contract amortization — 5 — 5 — 5 Other revenue (a)(c) — 36 32 68 — 68 Total operating revenue 2,203 1,055 524 1,579 (721 ) 3,061 Less: Lease revenue 3 — 3 3 — 6 Less: Derivative revenue 1 1,160 55 1,215 (241 ) 975 Less: Contract amortization — 5 — 5 — 5 Total revenue from contracts with customers $ 2,199 $ (110 ) $ 466 $ 356 $ (480 ) $ 2,075 (a) The following amounts of energy and capacity revenue relate to derivative instruments and are accounted for under ASC 815. Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue $ — $ 896 $ (25 ) $ 871 $ — $ 871 Capacity revenue — — 45 45 — 45 Other revenue — (4 ) 8 4 — 4 (b) Revenue relates entirely to unrealized gains and losses on derivative instruments accounted for under ASC 815. (c) Included in other revenue is lease revenue of $3 million for both Retail and East/West/Other, respectively. Nine months ended September 30, 2018 Generation (In millions) Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue (a) $ — $ 1,558 $ 735 $ 2,293 $ (890 ) $ 1,403 Capacity revenue (a) — 201 — 487 — 688 — 688 Retail revenue Mass customers 4,321 — — — (4 ) 4,317 Business Solutions customers 1,181 — — — — 1,181 Total retail revenue 5,502 — — — (4 ) 5,498 Mark-to-market for economic hedging activities (b) (5 ) (7 ) 2 (5 ) (21 ) (31 ) Contract amortization — 12 — 12 — 12 Other revenue (c) — 164 64 228 (3 ) 225 Total operating revenue 5,497 1,928 1,288 3,216 (918 ) 7,795 Less: Lease revenue 10 — 6 6 — 16 Less: Derivative revenue (5 ) 1,871 135 2,006 — 2,001 Less: Contract amortization — 12 — 12 — 12 Total revenue from contracts with customers $ 5,492 $ 45 $ 1,147 $ 1,192 $ (918 ) $ 5,766 (a) The following amounts of energy and capacity revenue relate to derivative instruments and are accounted for under ASC 815. Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue $ — $ 1,877 $ 7 $ 1,884 $ — $ 1,884 Capacity revenue — — 110 110 — 110 Other revenue — 1 16 17 — 17 (b) Revenue relates entirely to unrealized gains and losses on derivative instruments accounted for under ASC 815. (c) Included in other revenue is lease revenue of $10 million and $6 million for Retail and East/West/Other, respectively. Contract Amortization Assets and liabilities recognized from power sales agreements assumed at Fresh Start and through acquisitions related to the sale of electric capacity and energy in future periods for which the fair value has been determined to be significantly less (more) than market are amortized to revenue over the term of each underlying contract based on actual generation and/or contracted volumes. Lease Revenue Certain of the Company’s revenues are obtained through leases of rooftop residential solar systems, which are accounted for as operating leases in accordance with ASC 840, Leases. Pursuant to the lease agreements, the customers’ monthly payments are pre-determined fixed monthly amounts and may include an annual fixed percentage escalation to reflect the impact of utility rate increases over the lease term, which is 20 years. The Company records operating lease revenue on a straight-line basis over the life of the lease term. Certain customers made initial down payments that are being amortized over the life of the lease. The difference between the payments received and the revenue recognized is recorded as deferred revenue. Contract Balances The following table reflects the contract assets and liabilities included in the Company’s balance sheet as of September 30, 2018 : (In millions) September 30, 2018 Deferred customer acquisition costs $ 104 Accounts receivable, net - Contracts with customers 1,265 Accounts receivable, net - Derivative instruments 32 Total accounts receivable, net $ 1,297 Unbilled revenues (included within Accounts receivable, net - Contracts with customers) 385 Deferred revenues 60 The Company’s customer acquisition costs consist of broker fees, commission payments and other costs that represent incremental costs of obtaining the contract with customers for which the Company expects to recover. The Company amortizes these amounts over the estimated life of the customer contract. As a practical expedient, the Company expenses the incremental costs of obtaining a contract if the amortization period of the asset would have been one year or less. When the Company receives consideration from the customer that is in excess of the amount due, such consideration is reclassified to deferred revenue, which represents a contract liability. Generally, the Company will recognize revenue from contract liabilities in the next period as the Company satisfies its performance obligations. Recent Accounting Developments - Guidance Adopted in 2018 ASU 2017-07 — In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715) , Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, or ASU No. 2017-07. Current GAAP does not indicate where the amount of net benefit cost should be presented in an entity’s income statement and does not require entities to disclose the amount of net benefit cost that is included in the income statement. The amendments of ASU No. 2017-07 require an entity to report the service cost component of net benefit costs in the same line item as other compensation costs arising from services rendered by the related employees during the applicable service period. The other components of net benefit cost are required to be presented separately from the service cost component and outside the subtotal of income from operations. Further, ASU No. 2017-07 prescribes that only the service cost component of net benefit costs is eligible for capitalization. The Company adopted the amendments of ASU No. 2017-07 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance retrospectively which resulted in an increase in cost of operations of $4 million and $13 million with a corresponding increase in other income, net on the statement of operations for the three and nine months ended September 30, 2017 , respectively. ASU 2016-01 - In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , or ASU No. 2016-01. The amendments of ASU No. 2016-01 eliminate available-for-sale classification of equity investments and require that equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) be generally measured at fair value with changes in fair value recognized in net income. Further, the amendments require that financial assets and financial liabilities be presented separately in the notes to the financial statements, grouped by measurement category and form of financial asset. The guidance in ASU No. 2016-01 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those annual periods. The Company adopted the amendments of ASU No. 2016-01 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance on a modified retrospective basis, which resulted in no material adjustments recorded to the consolidated results of operations, cash flows, and statement of financial position. Recent Accounting Developments - Guidance Not Yet Adopted ASU 2018-15 - In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other- Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , or ASU No. 2018-15. The amendments of ASU No. 2018-15 addresses customer’s accounting for implementation costs incurred in a cloud computing arrangement that is a service contract and also adds certain disclosure requirements related to implementation costs incurred for internal-use software and cloud computing arrangements. The amendment aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). ASU No. 2018-15 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted. The amendments in ASU No. 2018-15 can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is evaluating the impact of adopting this guidance on the consolidated financial statements and disclosures. ASU 2018-14 - In August 2018, the FASB issued ASU No. 2018-14, Compensation - Retirement benefits (Topic 715-20): Disclosure Framework - Changes to Disclosure Requirements for Defined Benefit Plans , or ASU No. 2018-14. The guidance in ASU No. 2018-14 adds, removes and clarifies disclosure requirements related to defined benefit pension and other postretirement plans. The amendments in ASU No. 2018-14 eliminate the requirement to disclose the amounts in accumulated other comprehensive income expected to be recognized as part of net periodic benefit cost over the next year. The guidance also removes the disclosure requirements for the effects of a one-percentage-point change on the assumed health care costs and the effect of this change in rates on service cost, interest cost and the benefit obligation for postretirement health care benefits. ASU No. 2018-14 is effective for fiscal years ending after December 15, 2020 and must be applied on a retrospective basis. As the amendment contemplates changes in disclosures only, it will have no material impact on the Company's results of operations, cash flows, or statement of financial position. ASU 2018-13 - In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirement for Fair value Measurement) , or ASU No. 2018-13. The guidance in ASU No. 2018-13 eliminates such disclosures as the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy. The amendments in ASU No. 2018-13 add new disclosure requirements for Level 3 measurements. ASU No. 2018-13 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted for any eliminated or modified disclosures. Certain disclosures in ASU No. 2018-13 are required to be applied on a retrospective basis and others on a prospective basis. As the amendment contemplates changes in disclosures only, it will have no material impact on the Company's results of operations, cash flows, or statement of financial position. ASU 2016-02 — In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) , or Topic 842, with the objective to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and to improve financial reporting by expanding the related disclosures. The guidance in Topic 842 provides that a lessee that may have previously accounted for a lease as an operating lease under current GAAP should recognize the assets and liabilities that arise from a lease on the balance sheet. In addition, Topic 842 expands the required quantitative and qualitative disclosures with regards to lease arrangements. The Company will adopt the standard effective January 1, 2019, and expects to elect certain of the practical expedients permitted, including the expedient that permits the Company to retain its existing lease assessment and classification. The Company is currently working through an adoption plan which includes the evaluation of lease contracts compared to the new standard. While the Company is currently evaluating the impact the new guidance will have on its financial position and results of operations, the Company expects to recognize lease liabilities and right of use assets. The extent of the increase to assets and liabilities associated with these amounts remains to be determined pending the Company’s review of its existing lease contracts and service contracts which may contain embedded leases. While this review is still in process, NRG believes the adoption of Topic 842 will have a material impact on its financial statements. The Company is also monitoring recent changes to Topic 842 and the related impact on the implementation process.

Acquisitions, Discontinued Oper

Acquisitions, Discontinued Operations and Dispositions	9 Months Ended
	Sep. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Acquisitions, Discontinued Operations and Dispositions	Acquisitions, Discontinued Operations and Dispositions This footnote should be read in conjunction with the complete description under Note 3 , Discontinued Operations, Acquisitions and Dispositions , to the Company's 2017 Form 10-K. Acquisitions XOOM Energy Acquisition — On June 1, 2018, the Company completed the acquisition of XOOM Energy, LLC, an electricity and natural gas retailer operating in 19 states, Washington, D.C. and Canada for approximately $219 million in cash, inclusive of approximately $54 million in payments for estimated working capital, which is subject to further adjustment. The acquisition increased NRG's retail portfolio by approximately 300,000 customers. The purchase price was provisionally allocated as follows: $2 million to cash, $8 million to restricted cash, $45 million to accounts receivable, $42 million to derivative assets, $170 million to customer relationships and contracts, $26 million to current and non-current assets, $25 million to accounts payable, $31 million to derivative liabilities, and $18 million to current and non-current liabilities. Small Book Acquisitions — Through the end of October 2018, the Company has agreed to acquire several books of customers totaling approximately 115,000 customers, along with brand names, for $44 million . Discontinued Operations Sale of Ownership in NRG Yield, Inc. and Renewables Platform On August 31, 2018, the Company completed the sale of its interests in NRG Yield, Inc. and its Renewables Platform to GIP, for total cash consideration of $1.348 billion . The Company has concluded that the divested businesses meet the criteria for discontinued operations, as the dispositions represent a strategic shift in the markets in which NRG operates. As such, all prior period results for the transaction have been reclassified as discontinued operations. In connection with the transaction, NRG entered into a transition services agreement to provide certain corporate services to the divested businesses. As a result of the sale of NRG Yield, Inc., the Company's indirect ownership interest in the Agua Caliente solar project was reduced from 51% to 35 %. As such, the Company no longer controls the project; and accordingly, no longer consolidates the project for financial reporting purposes. The Company recorded its ownership interest as an equity method investment upon deconsolidation resulting in a gain of $8 million. As part of the agreement to sell NRG Yield and the Renewables Platform, the Company agreed to indemnify NRG Yield for any increase in property taxes for certain solar properties. The indemnity term will expire at various dates between 2029 and 2039. NRG has determined that the payment of this indemnity is probable and has recorded the estimated present value of the obligation as of the closing date of the transaction of $153 million to other non-current liabilities with a corresponding loss from discontinued operations. In addition to the California property tax indemnity, there were additional commitments and advisory fees totaling approximately $50 million . The Company will also retain all costs associated with the development and ownership of the Patriot Wind project until its sale to a third party pursuant to a sale agreement. Carlsbad On February 6, 2018, NRG entered into an agreement with NRG Yield to sell 100% of the membership interests in Carlsbad Energy Holdings LLC, which owns the Carlsbad project, for $365 million of cash consideration. Though construction is not yet complete, the primary condition to close the Carlsbad transaction was the completion of the sale of NRG Yield and the Renewables Platform. As the sale of NRG Yield and the Renewables Platform has closed, the Company has concluded that the Carlsbad project meets the criteria for discontinued operations and accordingly, the financial information for all current and historical periods has been recast to reflect Carlsbad as a discontinued operation. The Company will continue to consolidate Carlsbad until the transaction is closed, which is currently anticipated for the first quarter of 2019. After the transaction closes, Carlsbad will continue to have a ground lease and easement agreement with NRG. The agreement has an initial term ending in 2039 with two ten year extensions. As a result of the transaction, additional commitments related to the project totaled $23 million . Summarized results of discontinued operations were as follows: Three months ended September 30, 2018 Three months ended September 30, 2017 Nine months ended September 30, 2018 Nine months ended September 30, 2017 (In millions) Operating revenues $ 280 $ 315 $ 925 $ 906 Operating costs and expenses (212 ) (242 ) (682 ) (690 ) Other expenses (44 ) (64 ) (165 ) (210 ) Gain/(loss) from operations of discontinued components, before tax 24 9 78 6 Income tax expense 9 4 4 2 Gain/(loss) from discontinued operations, net of tax 15 5 74 4 Loss on deconsolidation, net of tax (139 ) — (139 ) — California property tax indemnification (153 ) — (153 ) — Other Commitments, Indemnification and Fees (77 ) — (77 ) — Loss on disposal of discontinued operations, net of tax (369 ) — (369 ) — Gain/(Loss) from discontinued operations, net of tax $ (354 ) $ 5 $ (295 ) $ 4 The following table summarizes the major classes of assets and liabilities classified as discontinued operations as follows: (In millions) September 30, 2018 (a) December 31, 2017 (b) Cash and cash equivalents $ — $ 224 Restricted Cash — 229 Accounts receivable, net — 119 Other current assets 4 133 Current assets - discontinued operations 4 705 Property, plant and equipment, net 547 7,473 Equity investments in affiliates — 856 Intangible assets, net 8 1,240 Other non-current assets 5 612 Non-current assets - discontinued operations 560 10,181 Current portion of long term debt and capital leases 14 484 Accounts payable 37 169 Other current liabilities 1 211 Current liabilities - discontinued operations 52 864 Long-term debt and capital leases 545 6,673 Other non-current liabilities 2 186 Non-current liabilities - discontinued operations $ 547 $ 6,859 (a) Represents the Carlsbad project. (b) Represents the discontinued operations of NRG Yield, NRG's Renewable Platform and the Carlsbad project. Sale of Assets to NRG Yield, Inc. Prior to Discontinued Operations On June 19, 2018, the Company completed the UPMC Thermal Project and received cash consideration from NRG Yield of $ 84 million. On March 30, 2018, as part of the Transformation Plan, the Company sold to NRG Yield, Inc. 100 % of NRG's interests in Buckthorn Renewables, LLC, which owns a 154 MW construction-stage utility-scale solar generation project, located in Texas. NRG Yield, Inc. paid cash consideration of approximately $42 million, excluding working capital adjustments, and assumed non-recourse debt of approximately $183 million. On March 27, 2017, the Company sold to NRG Yield, Inc.: (i) a 16% interest in the Agua Caliente solar project, representing ownership of approximately 46 net MW of capacity and (ii) NRG's interests in seven utility-scale solar projects located in Utah representing 265 net MW of capacity, which have reached commercial operations. NRG Yield, Inc. paid cash consideration of $130 million, plus $1 million in working capital adjustments, and assumed non-recourse debt of approximately $328 million. GenOn On June 14, 2017, the GenOn Entities filed voluntary petitions for relief under Chapter 11 of the Bankruptcy Code in the Bankruptcy Court. As a result of the bankruptcy filings, NRG has concluded that it no longer controls GenOn as it is subject to the control of the Bankruptcy Court; and, accordingly, NRG no longer consolidates GenOn for financial reporting purposes. By eliminating a large portion of its operations in the PJM market with the deconsolidation of GenOn, NRG has concluded that GenOn meets the criteria for discontinued operations, as this represents a strategic shift in the markets in which NRG operates. As such, all prior period results for GenOn have been reclassified as discontinued operations. Summarized results of discontinued operations were as follows: Three months ended September 30, 2018 Three months ended September 30, 2017 Nine months ended September 30, 2018 Nine months ended September 30, 2017 (In millions) Operating revenues $ — $ — $ — $ 646 Operating costs and expenses — — — (700 ) Other expenses — — — (98 ) Loss from operations of discontinued components, before tax — — — (152 ) Income tax expense — — — 9 Loss from discontinued operations — — — (161 ) Interest income - affiliate — — 3 6 Loss from discontinued operations, net of tax — — 3 (155 ) Pre-tax loss on deconsolidation — — — (208 ) Settlement consideration and services credit — — 1 (289 ) Pension and post-retirement liability assumption — (25 ) (2 ) (144 ) Other — (2 ) (27 ) (6 ) Loss on disposal of discontinued operations, net of tax — (27 ) (28 ) (647 ) Loss from discontinued operations, net of tax $ — $ (27 ) $ (25 ) $ (802 ) GenOn Settlement Effective July 16, 2018, NRG and GenOn consummated the GenOn Settlement which accelerated certain terms contemplated by the plan of reorganization, as further described below. As a result, the Company paid GenOn approximately $125 million , which included (i) the settlement consideration of $261 million , (ii) the transition services credit of $28 million and (iii) the return of $15 million of collateral posted to NRG; offset by the (i) $151 million in borrowings under the intercompany secured revolving credit facility, (ii) related accrued interest and fees of $12 million , (iii) remaining payments due under the transition services agreement of $10 million and (iv) certain other balances due to NRG totaling $6 million . The Company has reserved for all amounts deemed to be uncollectible. In order to facilitate the consummation of the GenOn Settlement, among other items, NRG assigned to GenOn approximately $8 million of historical claims against REMA in exchange for $4.2 million , which was credited as a reduction of the settlement payment. GenOn also indemnified NRG for any potential claims by REMA up to the amount of $10 million , and posted a letter of credit in that amount in favor of NRG as security for the indemnification. That letter of credit was subsequently released upon REMA's election to participate in the releases under GenOn's chapter 11 plan in favor of NRG. Other than those obligations which survive or are independent of the releases described herein, the GenOn Settlement and the GenOn chapter 11 plan provide NRG releases from GenOn and each of its debtor and non-debtor subsidiaries. On October 16, 2018, REMA and its subsidiaries filed voluntary petitions for chapter 11 relief and a prepackaged plan of reorganization in the United States Bankruptcy Court for the Southern District of Texas. The REMA debtors' plan of reorganization has been formally accepted by REMA's voting creditors and is consistent with the releases NRG receives under the GenOn Settlement and the GenOn plan. Restructuring Support Agreement Prior to the filing of GenOn's bankruptcy case, NRG, GenOn and certain holders representing greater than 93% in aggregate principal amount of GenOn’s Senior Notes and certain holders representing greater than 93% in aggregate principal amount of GenOn Americas Generation’s Senior Notes entered into a Restructuring Support Agreement that provided for a restructuring and recapitalization of the GenOn Entities through a prearranged plan of reorganization. In December 2017, the Bankruptcy Court approved the plan of reorganization, pursuant to an order of confirmation. Consummation of the plan of reorganization has not yet occurred and remains subject to the satisfaction or waiver of certain conditions precedent. Certain principal terms of the plan of reorganization are detailed below: 1) The dismissal of certain prepetition litigation and full releases from GenOn and each of its debtor and non-debtor subsidiaries in favor of NRG, excluding REMA. 2) NRG provided settlement cash consideration to GenOn of $261.3 million , paid in cash less amounts owed to NRG under the intercompany secured revolving credit facility. See Note 14 , Related Party Transactions for further discussion of the intercompany secured revolving credit facility. The net liability for these amounts, along with the services credit described below, is recorded in accrued expenses and other current liabilities - affiliate as of September 30, 2018 and December 31, 2017 . 3) NRG will retain the pension liability, including payment of approximately $13 million of 2017 pension contributions, for GenOn employees for service provided prior to the completion of the reorganization, which was paid in September 2017. GenOn’s pension liability as of September 30, 2018 , was approximately $76 million . NRG will also retain the liability for GenOn’s post-employment and retiree health and welfare benefits, in an amount up to $25 million . These liabilities are recorded within other non-current liabilities as of September 30, 2018 and December 31, 2017 . 4) The shared services agreement between NRG and GenOn was terminated and replaced as of the plan confirmation date with a 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. See Note 14 , Related Party Transactions , for further discussion of the Services Agreement. 5) NRG provided a credit of $28 million to GenOn to apply against amounts owed under the transition services agreement. The unused credit of approximately $18 million was paid in cash to GenOn. The credit was intended to reimburse GenOn for its payment of financing costs. 6) NRG and GenOn also agreed to cooperate in good faith to maximize the value of certain development projects. Pursuant to this, GenOn made a one-time payment in the amount of $15 million to NRG in December 2017 as compensation for a purchase option with respect to the Canal 3 project. During the second quarter of 2018, NRG sold Canal 3 to Stonepeak Kestrel Holdings II LLC, or Stonepeak Kestrel, in conjunction with GenOn's sale of Canal Units 1 and 2 to Stonepeak Kestrel Holdings LLC. NRG reimbursed GenOn for $13.5 million of the one-time payment upon the closing of the sale of Canal 3. GenMA Settlement The Bankruptcy Court order confirming the plan of reorganization also approved the settlement terms agreed to among the GenOn Entities, NRG, the Consenting Holders, GenOn Mid-Atlantic, and certain of GenOn Mid-Atlantic’s stakeholders, or the GenMA Settlement, and directed the settlement parties to cooperate in good faith to negotiate definitive documentation consistent with the GenMA Settlement term sheet in order to pursue consummation of the GenMA Settlement. The definitive documentation effectuating the GenMA Settlement was finalized and effective as of April 27, 2018. Certain terms of the compromise with respect to NRG and GenOn Mid-Atlantic are as follows: • Settlement of all pending litigation and objections to the Plan (including with respect to releases and feasibility); • NRG provided $37.5 million in letters of credit as new qualifying credit support to GenOn Mid-Atlantic; and • NRG paid approximately $6 million as reimbursement of professional fees incurred by certain of GenOn Mid-Atlantic's stakeholders in connection with the GenMA Settlement. Dispositions On November 1, 2018, the Company offered to Clearway Energy, Inc. its ownership interest in Agua Caliente Borrower 1, LLC, for approximately $120 million , which owns a 35% interest in Agua Caliente, a 290 MW utility-scale solar project located in Dateland, Arizona. The transaction is anticipated to close in the first quarter of 2019. On August 1, 2018, the Company completed the sale of 100% of its ownership interests in BETM to Diamond Energy Trading and Marketing, LLC for $71 million, net of working capital adjustments, which resulted in a gain of $15 million on the sale. The sale also resulted in the release and return of approximately $119 million of letters of credit, $32 million of parent guarantees, and $4 million of net cash collateral to NRG. On June 29, 2018, the Company completed the sale of Canal 3 to Stonepeak Kestrel for cash proceeds of approximately $16 million and recorded a gain of $17 million . Prior to the sale, Canal 3 entered into a financing arrangement and received cash proceeds of $167 million , of which $151 million was distributed to the Company. The related debt was non-recourse to NRG and was transferred to Stonepeak Kestrel in connection with the sale of Canal 3. In addition, the Company completed other asset sales for $12 million of cash proceeds during the nine months ended September 30, 2018.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments This footnote should be read in conjunction with the complete description under Note 4 , Fair Value of Financial Instruments , to the Company's 2017 Form 10-K. For cash and cash equivalents, funds deposited by counterparties, accounts and other receivables, accounts payable, restricted cash, and cash collateral paid and received in support of energy risk management activities, the carrying amount approximates fair value because of the short-term maturity of those instruments and are classified as Level 1 within the fair value hierarchy. The estimated carrying amounts and fair values of NRG's recorded financial instruments not carried at fair market value are as follows: As of September 30, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable (a) $ 11 $ 8 $ 2 $ 2 Liabilities: Long-term debt, including current portion (b) 7,331 7,653 9,482 9,739 (a) Includes the current portion of notes receivable which is recorded in prepayments and other current assets on the Company's consolidated balance sheets. (b) Excludes deferred financing costs, which are recorded as a reduction to long-term debt on the Company's consolidated balance sheets. The fair value of the Company's publicly-traded long-term debt is based on quoted market prices and is classified as Level 2 within the fair value hierarchy. The fair value of debt securities, non-publicly traded long-term debt and certain notes receivable of the Company are based on expected future cash flows discounted at market interest rates, or current interest rates for similar instruments with equivalent credit quality and are classified as Level 3 within the fair value hierarchy. The following table presents the level within the fair value hierarchy for long-term debt, including current portion as of September 30, 2018 and December 31, 2017 : As of September 30, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 7,385 $ 268 $ 7,432 $ 2,307 Recurring Fair Value Measurements Debt securities, equity securities, and trust fund investments, which are comprised of various U.S. debt and equity securities, and derivative assets and liabilities, are carried at fair market value. The following tables present assets and liabilities measured and recorded at fair value on the Company's condensed consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of September 30, 2018 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 21 $ 2 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 21 21 — — U.S. government and federal agency obligations 41 41 — — Federal agency mortgage-backed securities 88 — 88 — Commercial mortgage-backed securities 19 — 19 — Corporate debt securities 112 — 112 — Equity securities 368 368 — — Foreign government fixed income securities 4 — 4 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 1,022 210 743 69 Interest rate contracts 53 — 53 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 66 Total assets $ 1,816 $ 643 $ 1,019 $ 88 Derivative liabilities: Commodity contracts 905 271 552 82 Interest rate contracts 2 — 2 — Total liabilities $ 907 $ 271 $ 554 $ 82 As of December 31, 2017 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 22 $ 3 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 47 45 2 — U.S. government and federal agency obligations 43 42 1 — Federal agency mortgage-backed securities 82 — 82 — Commercial mortgage-backed securities 14 — 14 — Corporate debt securities 99 — 99 — Equity securities 334 334 — — Foreign government fixed income securities 5 — 5 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 744 191 509 44 Interest rate contracts 39 — 39 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 68 Total assets $ 1,498 $ 616 $ 751 $ 63 Derivative liabilities: Commodity contracts 674 257 358 59 Interest rate contracts 6 — 6 — Total liabilities $ 680 $ 257 $ 364 $ 59 There were no transfers during the three and nine months ended September 30, 2018 and 2017 between Levels 1 and 2. The following tables reconcile, for the three and nine months ended September 30, 2018 and 2017 , the beginning and ending balances for financial instruments that are recognized at fair value in the condensed consolidated financial statements, at least annually, using significant unobservable inputs: Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended September 30, 2018 Nine months ended September 30, 2018 (In millions) Debt Securities Derivatives (a) Total Debt Securities Derivatives (a) Total Beginning balance $ 19 $ 174 $ 193 $ 19 $ (15 ) $ 4 Contracts acquired in Xoom acquisition — — — — 12 12 Total losses — realized/unrealized — — — — (15 ) (15 ) Purchases — 12 12 — 9 9 Transfers into Level 3 (b) — (201 ) (201 ) — (4 ) (4 ) Transfers out of Level 3 (b) — 2 2 — — — Ending balance as of September 30, 2018 $ 19 $ (13 ) $ 6 $ 19 $ (13 ) $ 6 Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of September 30, 2018 — (3 ) (3 ) — (18 ) (18 ) (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2. Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended September 30, 2017 Nine months ended September 30, 2017 (In millions) Debt Securities Derivatives (a) Total Debt Securities Derivatives (a) Total Beginning balance $ 18 $ (9 ) $ 9 $ 17 $ (64 ) $ (47 ) Total gains/(losses) — realized/unrealized included in earnings 1 (32 ) (31 ) 2 12 14 Purchases — (9 ) (9 ) — — — Transfers into Level 3 (b) — (7 ) (7 ) — (11 ) (11 ) Transfers out of Level 3 (b) — 7 7 — 13 13 Ending balance as of September 30, 2017 $ 19 $ (50 ) $ (31 ) $ 19 $ (50 ) $ (31 ) Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of September 30, 2017 — (16 ) (16 ) — (12 ) (12 ) (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2. Derivative Fair Value Measurements A portion of NRG's contracts are exchange-traded contracts with readily available quoted market prices. A majority of NRG's contracts are non-exchange-traded contracts valued using prices provided by external sources, primarily price quotations available through brokers or over-the-counter and on-line exchanges. The remainder of the assets and liabilities represent contracts for which external sources or observable market quotes are not available for the whole term or for certain delivery months or the contracts are retail and load following power contracts. These contracts are valued using various valuation techniques including but not limited to internal models that apply fundamental analysis of the market and corroboration with similar markets. As of September 30, 2018 , contracts valued with prices provided by models and other valuation techniques make up 6% of the total derivative assets and 9% of the total derivative liabilities. NRG's significant positions classified as Level 3 include physical and financial power executed in illiquid markets as well as financial transmission rights, or FTRs. The significant unobservable inputs used in developing fair value include illiquid power location pricing which is derived as a basis to liquid locations. The basis spread is based on observable market data when available or derived from historic prices and forward market prices from similar observable markets when not available. For FTRs, NRG uses the most recent auction prices to derive the fair value. The following tables quantify the significant unobservable inputs used in developing the fair value of the Company's Level 3 positions as of September 30, 2018 and December 31, 2017 : Significant Unobservable Inputs September 30, 2018 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 44 $ 68 Discounted Cash Flow Forward Market Price (per MWh) $ 2 $ 197 $ 23 FTRs 25 14 Discounted Cash Flow Auction Prices (per MWh) (90 ) 86 — $ 69 $ 82 Significant Unobservable Inputs December 31, 2017 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 33 $ 47 Discounted Cash Flow Forward Market Price (per MWh) $ 10 $ 142 $ 24 FTRs 11 12 Discounted Cash Flow Auction Prices (per MWh) (28 ) 46 — $ 44 $ 59 The following table provides sensitivity of fair value measurements to increases/(decreases) in significant unobservable inputs as of September 30, 2018 and December 31, 2017 : Significant Unobservable Input Position Change In Input Impact on Fair Value Measurement Forward Market Price Power Buy Increase/(Decrease) Higher/(Lower) Forward Market Price Power Sell Increase/(Decrease) Lower/(Higher) FTR Prices Buy Increase/(Decrease) Higher/(Lower) FTR Prices Sell Increase/(Decrease) Lower/(Higher) The fair value of each contract is discounted using a risk-free interest rate. In addition, the Company applies a credit reserve to reflect credit risk, which is calculated based on published default probabilities. As of September 30, 2018 , and December 31, 2017 , the credit reserve did not result in a significant change in fair value in operating revenue and cost of operations. Concentration of Credit Risk In addition to the credit risk discussion as disclosed in Note 2 , Summary of Significant Accounting Policies , to the Company's 2017 Form 10-K, the following is a discussion of the concentration of credit risk for the Company's contractual obligations. Credit risk relates to the risk of loss resulting from non-performance or non-payment by counterparties pursuant to the terms of their contractual obligations. NRG is exposed to counterparty credit risk through various activities including wholesale sales, fuel purchases and retail supply arrangements, and retail customer credit risk through its retail load activities. Counterparty Credit Risk The Company's counterparty credit risk policies are disclosed in its 2017 Form 10-K. As of September 30, 2018 , the Company's counterparty credit exposure, excluding credit risk exposure under certain long term agreements, was $290 million with net exposure of $251 million . NRG held collateral (cash and letters of credit) against those positions of $48 million . Approximately 76% of the Company's exposure before collateral is expected to roll off by the end of 2019 . Counterparty credit exposure is valued through observable market quotes and discounted at a risk free interest rate. The following tables highlight net counterparty credit exposure by industry sector and by counterparty credit quality. Net counterparty credit exposure is defined as the aggregate net asset position for NRG with counterparties where netting is permitted under the enabling agreement and includes all cash flow, mark-to-market and NPNS, and non-derivative transactions. The exposure is shown net of collateral held, and includes amounts net of receivables or payables. Net Exposure (a) (b) Category by Industry Sector (% of Total) Utilities, energy merchants, marketers and other 83 % Financial institutions 17 Total as of September 30, 2018 100 % Net Exposure (a) (b) Category by Counterparty Credit Quality (% of Total) Investment grade 59 % Non-Investment grade/Non-Rated 41 Total as of September 30, 2018 100 % (a) Counterparty credit exposure excludes uranium and coal transportation contracts because of the unavailability of market prices. (b) The figures in the tables above exclude potential counterparty credit exposure related to RTOs, ISOs, registered commodity exchanges and certain long term contracts. NRG has counterparty credit risk exposure to certain counterparties, each of which represent more than 10% of total net exposure discussed above. The aggregate of such counterparties' exposure was $60 million as of September 30, 2018 . Changes in hedge positions and market prices will affect credit exposure and counterparty concentration. Given the credit quality, diversification and term of the exposure in the portfolio, NRG does not anticipate a material impact on the Company's financial position or results of operations from nonperformance by any of NRG's counterparties. RTOs and ISOs The Company participates in the organized markets of CAISO, ERCOT, ISO-NE, MISO, NYISO and PJM, known as RTOs or ISOs. Trading in these markets is approved by FERC, or in the case of ERCOT, approved by the PUCT and includes credit policies that, under certain circumstances, require that losses arising from the default of one member on spot market transactions be shared by the remaining participants. As a result, the counterparty credit risk to these markets is limited to NRG’s share of overall market and are excluded from the above exposures. Exchange Traded Transactions The Company enters into commodity transactions on registered exchanges, notably ICE and NYMEX. These clearinghouses act as the counterparty and transactions are subject to extensive collateral and margining requirements. As a result, these commodity transactions have limited counterparty credit risk. Long Term Contracts Counterparty credit exposure described above excludes credit risk exposure under certain long term agreements, including California tolling agreements, Gulf Coast load obligations, and solar PPAs. As external sources or observable market quotes are not available to estimate such exposure, the Company estimates its credit exposure for these contracts based on various techniques including, but not limited to, internal models based on a fundamental analysis of the market and extrapolation of observable market data with similar characteristics. Based on these valuation techniques, as of September 30, 2018 , aggregate credit risk exposure managed by NRG to these counterparties was approximately $1.5 billion , for the next five years. This amount excludes potential credit exposures for projects with long-term PPAs that have not reached commercial operations. The majority of these power contracts are with utilities or public power entities with strong credit quality and public utility commission or other regulatory support. However, such regulated utility counterparties can be impacted by changes in government regulations or treatment by regulatory agencies which NRG is unable to predict. Retail Customer Credit Risk The Company is exposed to retail credit risk through the Company's retail electricity providers, which serve C&I customers and the Mass market. Retail credit risk results in losses when a customer fails to pay for services rendered. The losses may result from both nonpayment of customer accounts receivable and the loss of in-the-money forward value. The Company manages retail credit risk through the use of established credit policies that include monitoring of the portfolio and the use of credit mitigation measures such as deposits or prepayment arrangements. As of September 30, 2018 , the Company's retail customer credit exposure to C&I and Mass customers was diversified across many customers and various industries, as well as government entities.

Nuclear Decommissioning Trust F

Nuclear Decommissioning Trust Fund	9 Months Ended
	Sep. 30, 2018
Nuclear Decommissioning Trust Fund Disclosure [Abstract]
Nuclear Decommissioning Trust Fund	Nuclear Decommissioning Trust Fund This footnote should be read in conjunction with the complete description under Note 6 , Nuclear Decommissioning Trust Fund , to the Company's 2017 Form 10-K. NRG's Nuclear Decommissioning Trust Fund assets are comprised of securities classified as available-for-sale and recorded at fair value based on actively quoted market prices. NRG accounts for the Nuclear Decommissioning Trust Fund in accordance with ASC 980, Regulated Operations , because the Company's nuclear decommissioning activities are subject to approval by the PUCT with regulated rates that are designed to recover all decommissioning costs and that can be charged to and collected from the ratepayers per PUCT mandate. Since the Company is in compliance with PUCT rules and regulations regarding decommissioning trusts and the cost of decommissioning is the responsibility of the Texas ratepayers, not NRG, all realized and unrealized gains or losses (including other-than-temporary impairments) related to the Nuclear Decommissioning Trust Fund are recorded to the Nuclear Decommissioning Trust liability and are not included in net income or accumulated OCI, consistent with regulatory treatment. The following table summarizes the aggregate fair values and unrealized gains and losses (including other-than-temporary impairments) for the securities held in the trust funds, as well as information about the contractual maturities of those securities. As of September 30, 2018 As of December 31, 2017 (In millions, except otherwise noted) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Cash and cash equivalents $ 21 $ — $ — — $ 47 $ — $ — — U.S. government and federal agency obligations 41 1 1 12 43 1 — 11 Federal agency mortgage-backed securities 88 — 3 23 82 1 1 23 Commercial mortgage-backed securities 19 — 1 22 14 — — 20 Corporate debt securities 112 1 2 10 99 2 1 11 Equity securities 434 296 — — 402 272 — — Foreign government fixed income securities 4 — — 9 5 — — 9 Total $ 719 $ 298 $ 7 $ 692 $ 276 $ 2 The following table summarizes proceeds from sales of available-for-sale securities and the related realized gains and losses from these sales. The cost of securities sold is determined on the specific identification method. Nine months ended September 30, 2018 2017 (In millions) Realized gains $ 8 $ 8 Realized losses 8 6 Proceeds from sale of securities $ 398 $ 382

Accounting for Derivative Instr

Accounting for Derivative Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Accounting for Derivative Instruments and Hedging Activities	Accounting for Derivative Instruments and Hedging Activities This footnote should be read in conjunction with the complete description under Note 5 , Accounting for Derivative Instruments and Hedging Activities , to the Company's 2017 Form 10-K. Energy-Related Commodities As of September 30, 2018 , NRG had energy-related derivative instruments extending through 2030 . The Company marks these derivatives to market through the statement of operations. Interest Rate Swaps NRG is exposed to changes in interest rates through the Company's issuance of variable rate debt. In order to manage the Company's interest rate risk, NRG enters into interest rate swap agreements. As of September 30, 2018 , NRG had interest rate derivative instruments on recourse debt extending through 2021 , which are not designated as cash flow hedges. The Company had an interest rate swap on non-recourse debt extending through 2032 , which is not designated as a cash flow hedge. Volumetric Underlying Derivative Transactions The following table summarizes the net notional volume buy/(sell) of NRG's open derivative transactions broken out by category, excluding those derivatives that qualified for the NPNS exception, as of September 30, 2018 and December 31, 2017 . Option contracts are reflected using delta volume. Delta volume equals the notional volume of an option adjusted for the probability that the option will be in-the-money at its expiration date. Total Volume September 30, 2018 December 31, 2017 Category Units (In millions) Emissions Short Ton 3 1 Renewable Energy Certificates Certificates 1 — Coal Short Ton 8 21 Natural Gas MMBtu (439 ) (20 ) Power MWh 8 23 Capacity MW/Day (1 ) (1 ) Interest Dollars $ 1,058 $ 1,060 Equity Shares — 1 The increase in the natural gas position was primarily the result of additional generation hedge positions. Fair Value of Derivative Instruments The following table summarizes the fair value within the derivative instrument valuation on the balance sheets: Fair Value Derivative Assets Derivative Liabilities September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (In millions) Derivatives Not Designated as Cash Flow or Fair Value Hedges: Interest rate contracts current 17 8 — 1 Interest rate contracts long-term 36 31 2 5 Commodity contracts current 666 616 550 536 Commodity contracts long-term 356 128 355 138 Total Derivatives Not Designated as Cash Flow or Fair Value Hedges 1,075 783 907 680 The Company has elected to present derivative assets and liabilities on the balance sheet on a trade-by-trade basis and does not offset amounts at the counterparty master agreement level. In addition, collateral received or paid on the Company's derivative assets or liabilities are recorded on a separate line item on the balance sheet. The following table summarizes the offsetting of derivatives by counterparty master agreement level and collateral received or paid: Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of September 30, 2018 (In millions) Commodity contracts: Derivative assets $ 1,022 $ (765 ) $ (18 ) $ 239 Derivative liabilities (905 ) 765 30 (110 ) Total commodity contracts 117 — 12 129 Interest rate contracts: Derivative assets 53 — — 53 Derivative liabilities (2 ) — — (2 ) Total interest rate contracts 51 — — 51 Total derivative instruments $ 168 $ — $ 12 $ 180 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of December 31, 2017 (In millions) Commodity contracts: Derivative assets $ 744 $ (578 ) $ (11 ) $ 155 Derivative liabilities (674 ) 578 72 (24 ) Total commodity contracts 70 — 61 131 Interest rate contracts: Derivative assets 39 — — 39 Derivative liabilities (6 ) — — (6 ) Total interest rate contracts 33 — — 33 Total derivative instruments $ 103 $ — $ 61 $ 164 Accumulated Other Comprehensive Loss The following table summarizes the effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax: Interest Rate Contracts Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 (In millions) Accumulated OCI beginning balance $ (23 ) $ (67 ) $ (54 ) $ (66 ) Reclassified from accumulated OCI to income: Due to realization of previously deferred amounts 1 4 8 10 Mark-to-market of cash flow hedge accounting contracts (3 ) 4 21 (3 ) Sale of NRG Yield and the Renewables Platform 25 — 25 — Accumulated OCI ending balance, net of $0, and $15 tax $ — $ (59 ) $ — $ (59 ) Amounts reclassified from accumulated OCI into income are recorded in discontinued operations. The Company's regression analysis for Marsh Landing, Walnut Creek, and Avra Valley interest rate swaps, while positively correlated, no longer contain match terms for cash flow hedge accounting. As a result, the Company voluntarily de-designated the Marsh Landing, Walnut Creek, and Avra Valley cash flow hedges as of April 28, 2017, and prospectively marked these derivatives to market through the income statement until the assets were sold. Impact of Derivative Instruments on the Statements of Operations Unrealized gains and losses associated with changes in the fair value of derivative instruments not accounted for as cash flow hedges are reflected in current period consolidated results of operations. The following table summarizes the pre-tax effects of economic hedges that have not been designated as cash flow hedges and trading activity on the Company's statement of operations. The effect of energy commodity contracts is included within operating revenues and cost of operations and the effect of interest rate contracts is included in interest expense. Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 Unrealized mark-to-market results (In millions) Reversal of previously recognized unrealized (gains)/losses on settled positions related to economic hedges $ (84 ) $ (7 ) $ (85 ) $ 18 Reversal of acquired gain positions related to economic hedges (10 ) (2 ) (11 ) (1 ) Net unrealized gains/(losses) on open positions related to economic hedges 25 (19 ) 158 (8 ) Total unrealized mark-to-market (losses)/gains for economic hedging activities (69 ) (28 ) 62 9 Reversal of previously recognized unrealized gains on settled positions related to trading activity (4 ) (5 ) (10 ) (24 ) Net unrealized gains on open positions related to trading activity 8 — 27 17 Total unrealized mark-to-market gains/(losses) for trading activity 4 (5 ) 17 (7 ) Total unrealized (losses)/gains $ (65 ) $ (33 ) $ 79 $ 2 Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 (In millions) Unrealized gains/(losses) included in operating revenues $ 59 $ 17 $ (14 ) $ 170 Unrealized (losses)/gains included in cost of operations (124 ) (50 ) 93 (168 ) Total impact to statement of operations — energy commodities $ (65 ) $ (33 ) $ 79 $ 2 Total impact to statement of operations — interest rate contracts $ 2 $ 3 $ 17 $ (4 ) The reversals of acquired gain or loss positions were valued based upon the forward prices on the acquisition date. The roll-off amounts were offset by realized gains or losses at the settled prices and are reflected in operating revenue or cost of operations during the same period. For the nine months ended September 30, 2018 , the $158 million unrealized gain from open economic hedge positions was primarily the result of an increase in value of forward purchases of ERCOT heat rate and ERCOT electricity contracts due to ERCOT heat rate expansion and increases in ERCOT power prices. For the nine months ended September 30, 2017 , the $8 million unrealized loss from open economic hedge positions was primarily the result of a decrease in value of forward purchases of coal, natural gas, and ERCOT power due to decreases in coal, natural gas, and ERCOT electricity prices, which was largely offset by an increase in value of forward sales of PJM power and New York capacity due to decreases in PJM electricity and New York capacity prices. Credit Risk Related Contingent Features Certain of the Company's hedging agreements contain provisions that require the Company to post additional collateral if the counterparty determines that there has been deterioration in credit quality, generally termed “adequate assurance” under the agreements, or require the Company to post additional collateral if there were a one notch downgrade in the Company's credit rating. The collateral required for contracts with adequate assurance clauses that are in a net liability position as of September 30, 2018 , was $25 million . The collateral required for contracts with credit rating contingent features that are in a net liability position as of September 30, 2018 , was $17 million . The Company is also a party to certain marginable agreements under which it has a net liability position, but the counterparty has not called for the collateral due, which was approximately $6 million as of September 30, 2018 . See Note 4 , Fair Value of Financial Instruments , to this Form 10-Q for discussion regarding concentration of credit risk.

Impairments

Impairments	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Impairments	Impairments 2018 Impairment Losses Keystone and Conemaugh — On June 29, 2018, the Company entered into an agreement to sell its approximately 3.7% interests in the Keystone and Conemaugh generating stations. NRG recorded impairment losses of $14 million for Keystone and $14 million for Conemaugh to adjust the carrying amount of the assets to fair value based on the contractual sale price. The transaction closed on September 5, 2018. Dunkirk — During the second quarter of 2018, NRG ceased its development of the project to add gas capability at the Dunkirk generating station. The project was put on hold in 2015 pending the resolution of a lawsuit filed by Entergy Corporation against the NYPSC which challenged the legality of the Dunkirk contract. The lawsuit was later dropped and development continued, but the delay imposed a new requirement on Dunkirk to enter into the NYISO interconnection study process. The NYISO studies have concluded that extensive electric system upgrades would be necessary for the station to return to service. This would cause the Company to incur a material increase in cost and delay the project schedule that would render the project impractical. Consequently, the Company has recorded an impairment loss of $46 million , reducing the carrying amount of the related assets to $0 . 2017 Impairment Losses Bacliff Project — On June 16, 2017, NRG Texas Power LLC provided notice to BTEC New Albany, LLC that it was exercising its right to terminate the Amended and Restated Membership Interest Purchase Agreement, or MIPA, due to the Bacliff Project, a new peaking facility at the former P.H. Robinson Electric Generating Station, not achieving commercial completion by the contractual expiration date of May 31, 2017. As a result of the MIPA termination, the Company recorded an impairment loss of $41 million to reduce the carrying amount of the related construction in progress to $0 during the second quarter of 2017. Subsequent to the MIPA termination, BTEC filed claims against NRG Texas Power LLC with respect to the termination of the MIPA and NRG filed counterclaims against BTEC as further described in Note 15 , Commitments and Contingencies . On June 7, 2018, the parties resolved all claims and counterclaims in the lawsuit. Other Impairments — As of September 30, 2017 , the Company recorded impairment losses of approximately $19 million in connection with the renewable assets that were not divested as part of the sale of NRG Yield and the Renewables Platform.

Debt and Capital Leases

Debt and Capital Leases	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt and Capital Leases	Debt and Capital Leases This footnote should be read in conjunction with the complete description under Note 12 , Debt and Capital Leases , to the Company's 2017 Form 10-K. Long-term debt and capital leases consisted of the following: (In millions, except rates) September 30, 2018 December 31, 2017 September 30, 2018 interest rate % (a) Recourse debt: Senior Notes, due 2022 $ 485 $ 992 6.250 Senior Notes, due 2024 733 733 6.250 Senior Notes, due 2026 1,000 1,000 7.250 Senior Notes, due 2027 1,230 1,250 6.625 Senior Notes, due 2028 821 870 5.750 Convertible Senior Notes, due 2048 575 — 2.750 Term loan facility, due 2023 1,857 1,872 L+1.75 Tax-exempt bonds 466 465 4.125 - 6.00 Subtotal recourse debt 7,167 7,182 Non-recourse debt: Ivanpah, due 2033 and 2038 (b) — 1,073 2.285 - 4.256 Agua Caliente, due 2037 (c) — 818 2.395 - 3.633 Agua Caliente Borrower 1, due 2038 86 89 5.430 Midwest Generation, due 2019 78 152 4.390 Other 105 180 various Subtotal all non-recourse debt 269 2,312 Subtotal long-term debt (including current maturities) 7,436 9,494 Capital leases 2 5 various Subtotal long-term debt and capital leases (including current maturities) 7,438 9,499 Less current maturities (593 ) (204 ) Less debt issuance costs (82 ) (103 ) Discounts (105 ) (12 ) Total long-term debt and capital leases $ 6,658 $ 9,180 (a) As of September 30, 2018 , L+ equals 3-month LIBOR plus 1.75% . (b) The Company deconsolidated Ivanpah during the second quarter of 2018. (c) The Company deconsolidated Agua Caliente solar facility during the third quarter of 2018. Recourse Debt 2023 Term Loan Facility On March 21, 2018, NRG repriced the 2023 Term Loan Facility, reducing the interest rate margin by 50 basis points to LIBOR plus 1.75% and reducing the LIBOR floor to 0.00% . In accordance with the terms of the Credit Agreement, on October 5, 2018, the Company initiated an asset sale offer to purchase a portion of its Term Loan following the sale of NRG Yield and the Renewables Platform. The offer expired on November 5, 2018, and $260 million of Term Loan holders accepted the offer. As a result, the Company prepaid $155 million of Term Loans as part of its de-leveraging plan, as well as established an incremental first lien secured loan term facility under the Senior Credit Facility in the aggregate principal amount of $105 million on the same terms and conditions to stay within its debt reduction target. Senior Notes Issuance of 2048 Convertible Senior Notes During the second quarter of 2018, NRG issued $575 million in aggregate principal amount of 2.75% Convertible Senior Notes due 2048, or the Convertible Notes. The Convertible Notes are convertible, under certain circumstances, into the Company's common stock, cash or a combination thereof (at NRG's option) at an initial conversion price of $47.74 per common share, which is equivalent to an initial conversion rate of approximately 20.9479 shares of common stock per $1,000 principal amount of Convertible Notes. Interest on the Convertible Notes is payable semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2018. The Convertible Notes mature on June 1, 2048, unless earlier repurchased, redeemed or converted in accordance with their terms. The Convertible Notes are guaranteed by certain NRG subsidiaries. Prior to the close of business on the business day immediately preceding December 1, 2024, the Convertible Notes will be convertible only upon the occurrence of certain events and during certain periods, and thereafter during specified periods as follows: • from December 1, 2024 until the close of business on the second scheduled trading day immediately before June 1, 2025; and • from December 1, 2047 until the close of business on the second scheduled trading day immediately before the maturity date. The Convertible Notes are accounted for in accordance with ASC 470-20, Debt with Conversion and Other Options . Under ASC 470-20, issuers of convertible debt instruments that may be settled in cash upon conversion, including partial cash settlement, are required to separately account for the liability (debt) and equity (conversion option) components. The carrying amount of the liability component at issuance date of $472 million was calculated by estimating the fair value of similar liabilities without a conversion feature. The residual principal amount of the notes of $103 million was allocated to the equity component with offset to debt discount. The debt discount will be amortized to interest expense using the effective interest method over seven years which is determined to be the expected life of the Convertible Notes. The Company incurred approximately $12 million in transaction costs in connection with the issuance of the notes. These costs were allocated to the liability and equity components in proportion to the allocation of proceeds. Transaction costs of $10 million , allocated to the liability component, were recognized as deferred financing costs and are amortized over the seven years. Transaction costs of $2 million , allocated to the equity component, were recognized as a reduction of additional paid-in capital. Senior Note Repurchases In order to remain leverage neutral with the issuance of the Convertible Notes, during the second and third quarter, the Company completed open market senior note repurchases and partially redeemed the 6.250% notes due 2022, as detailed in the table below. During the nine months ended September 30, 2018 , a $22 million loss on debt extinguishment was recorded for these repurchases, which included the write-off of previously deferred financing costs of $6 million . Principal Repurchased Cash Paid (a) Average Early Redemption Percentage In millions, except rates 5.750% senior notes due 2028 $ 29 $ 30 99.24 % 6.250% senior notes due 2022 14 15 103.25 % Total at June 30, 2018 $ 43 $ 45 6.250% senior notes due 2022 (b) 492 512 103.13 % 5.750% senior notes due 2028 20 20 99.13 % 6.625% senior notes due 2027 20 21 103.06 % Total at September 30, 2018 $ 575 $ 598 (a) Includes payment for accrued interest of $7 million as of September 30, 2018 (b) Includes partial redemption of $486 million during the third quarter of 2018 On October 9, 2018, the Company redeemed all of its outstanding 6.250% senior notes due 2022 in the aggregate principal amount of $485 million . The Company has completed its targeted $640 million debt reduction, through this redemption and the $155 million Term Loan repurchase, and is on track to achieve a target net debt to adjusted EBITDA ratio of 3.0 /1 for 2018.

Variable Interest Entities, or

Variable Interest Entities, or VIEs	9 Months Ended
	Sep. 30, 2018
Variable Interest Entities Disclosure [Abstract]
Variable Interest Entities, or VIEs	Variable Interest Entities, or VIEs Entities that are not Consolidated Through its consolidated subsidiary, NRG Solar Ivanpah LLC, NRG owns a 54.6% interest in Ivanpah Master Holdings LLC, or Ivanpah, the owner of three solar electric generating projects located in the Mojave Desert with a total capacity of 392 MW. NRG considers this investment a VIEs under ASC 810, Consolidation , and NRG is not considered the primary beneficiary. The Company accounts for its interest under the equity method of accounting. The Ivanpah solar electric generating projects were funded in large part by loans guaranteed by the U.S. DOE and equity from the projects' partners. During the first quarter of 2018, all interested parties sought a restructuring of Ivanpah's debt in order to avoid a potential event of default with respect to the loans in connection with several recent events. Ensuing negotiations culminated in a settlement during the second quarter of 2018 between the parties which resulted in certain transactions, including the release of reserves totaling $95 million to fund equity distributions to the partners, which reduced the equity at risk, and the prepayment of certain of the debt balance outstanding, and the amendment of certain of Ivanpah's governing documents. The equity distributions and prepayment of debt were funded by the agreed upon release of reserve funds. These events were considered to be a reconsideration event in accordance with ASC 810, Consolidation . As a result, NRG determined that it is not the primary beneficiary and deconsolidated Ivanpah. NRG recognized a loss of $22 million on the deconsolidation and subsequent recognition of Ivanpah as an equity method investment during the nine months ended September 30, 2018 . The deconsolidation of Ivanpah reduced the Company's assets by approximately $1.3 billion , which was primarily property, plant and equipment, and reduced the Company's liabilities by $1.2 billion , which was primarily long-term debt. NRG's maximum exposure to loss is limited to its equity investment, which was $45 million as of September 30, 2018 . Entities that are Consolidated The Company has a controlling financial interest in certain entities, which have been identified as VIEs under ASC 810. These arrangements are primarily related to tax equity arrangements entered into with third-parties in order to finance the cost of solar energy systems under operating leases eligible for certain tax credits as further described in Note 2 , Summary of Significant Accounting Policies to the Company's 2017 Form 10-K. The summarized financial information for the Company's consolidated VIEs consisted of the following: (In millions) September 30, 2018 December 31, 2017 Current assets $ 6 $ 6 Net property, plant and equipment 76 80 Other long-term assets 31 36 Total assets 113 122 Current liabilities 2 3 Long-term debt 29 30 Other long-term liabilities 8 7 Total liabilities 39 40 Redeemable noncontrolling interest 19 19 Net assets less noncontrolling interests $ 55 $ 63

Changes in Capital Structure

Changes in Capital Structure	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Changes in Capital Structure	Changes in Capital Structure As of September 30, 2018 and December 31, 2017 , the Company had 500,000,000 shares of common stock authorized. The following table reflects the changes in NRG's common stock issued and outstanding: Issued Treasury Outstanding Balance as of December 31, 2017 418,323,134 (101,580,045 ) 316,743,089 Shares issued under LTIPs 1,555,766 — 1,555,766 Shares issued under ESPP — 175,862 175,862 Shares repurchased — (28,544,693 ) (28,544,693 ) Balance as of September 30, 2018 419,878,900 (129,948,876 ) 289,930,024 Employee Stock Purchase Plan In January 2018, 175,862 shares of common stock were issued to employee accounts from treasury stock for the offering period of July 1, 2017, to December 31, 2017. In January 2018, NRG suspended the ESPP. Share Repurchases In February 2018, the Company's board of directors authorized the Company to repurchase $1 billion of its common stock. As of September 30, 2018, the Company has completed the $1 billion common stock repurchase program. The following repurchases have been made during the nine months ended September 30, 2018. Total number of shares purchased Average price paid per share Amounts paid for shares purchased (in millions) Board Authorized Share Repurchases First Quarter 2018 (a) 3,114,748 $ 93 Second Quarter 2018 (a) (b) 11,748,553 407 Third Quarter 2018 (b) 13,681,392 500 Total Board Authorized Share Repurchases as of September 30, 2018 28,544,693 (c) $ 1,000 (a) The average price paid per share and amounts paid for shares purchased exclude the commissions of $0.01 per share paid in connection with the open market share repurchase. (b) The share repurchases for the second and the third quarter include 9,969,023 and 13,681,392 respectively of the shares repurchased through the ASR Agreements, as described below. (c) The total number of shares repurchased under the $1 billion share repurchase program and the average price paid per share will be determined upon final settlement of the September ASR in which the financial institution may deliver additional shares to the Company. Accelerated Share Repurchase On May 24, 2018, the Company executed an accelerated share repurchase agreement, or ASR Agreement, with a financial institution to repurchase a total of $354 million of outstanding common stock based on a volume weighted average price. The Company received initial shares of 9,969,023 , which were recorded in treasury stock at fair value based on the closing price of $343 million , with the remaining $11 million recorded in additional paid in capital, representing the value of the forward contract to purchase additional shares. In July 2018, the financial institution delivered the remaining shares pursuant to the ASR Agreement and the Company received an additional 860,880 shares. The average price paid for all of the shares delivered under the ASR Agreement was $32.69 per share. Upon receipt of the additional shares, the Company transferred the $11 million from additional paid in capital to treasury stock. On September 5, 2018, the Company executed an additional ASR Agreement with a financial institution, to complete the remaining portion of the $1 billion stock repurchase program authorized by the Company's board of directors by repurchasing a total of $500 million of outstanding common stock based on a volume weighted average price less an agreed upon discount. The Company received initial shares of 12,820,512 , which were recorded in treasury stock at fair value based on the closing price on the day of the transaction of $452 million, with the remaining $48 million recorded in additional paid in capital, representing the value of the forward contract to purchase additional shares. The ASR agreement will settle on or before December 31, 2018. NRG Common Stock Dividends The following table lists the dividends paid during the nine months ended September 30, 2018 : Third Quarter 2018 Second Quarter 2018 First Quarter 2018 Dividends per Common Share $ 0.03 $ 0.03 $ 0.03 On October 17, 2018 , NRG declared a quarterly dividend on the Company's common stock of $0.03 per share, payable November 15, 2018 , to stockholders of record as of November 1, 2018 , representing $0.12 per share on an annualized basis. The Company's common stock dividends are subject to available capital, market conditions, and compliance with associated laws, regulations and other contractual obligations.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company's segment structure reflects how management currently makes financial decisions and allocates resources. The Company's businesses are segregated as follows: Generation, which includes generation, Renewables and international; Retail, which includes Mass customers and Business Solutions, which includes C&I customers and other distributed and reliability products; and corporate activities. The financial information for the three and nine months ended September 30, 2018 has been recast to reflect the current segment structure. On August 31, 2018, as described in Note 3 , Acquisitions, Discontinued Operations and Dispositions , NRG deconsolidated NRG Yield, Inc., its Renewables Platform and Carlsbad for financial reporting purposes. The financial information for all historical periods has been recast to reflect the presentation of these entities as discontinued operations within the corporate segment. On June 14, 2017, as described in Note 3 , Acquisitions, Discontinued Operations and Dispositions , NRG deconsolidated GenOn for financial reporting purposes. The financial information for all historical periods has been recast to reflect the presentation of GenOn as discontinued operations within the corporate segment. NRG’s chief operating decision maker, its chief executive officer, evaluates the performance of its segments based on operational measures including adjusted earnings before interest, taxes, depreciation and amortization, or Adjusted EBITDA, free cash flow and capital for allocation, as well as net income/(loss). Retail (a) Generation (a) Corporate (a) Eliminations Total Three months ended September 30, 2018 (In millions) Operating revenues (a) $ 2,203 $ 1,579 $ 1 $ (722 ) $ 3,061 Depreciation and amortization 30 73 7 2 112 Reorganization costs 6 3 18 — 27 Gain on sale of assets — — 14 — 14 Equity in earnings of unconsolidated affiliates — 20 2 (2 ) 20 Loss on debt extinguishment, net — — (19 ) — (19 ) (Loss)/income from continuing operations before income taxes (127 ) 595 349 (504 ) 313 (Loss)/income from continuing operations (127 ) 595 342 (504 ) 306 Loss from discontinued operations, net of tax — — (354 ) — (354 ) Net (Loss)/Income (127 ) 595 (12 ) (504 ) (48 ) (Loss)/Income attributable to NRG Energy, Inc. common stockholders $ (127 ) $ 579 $ (23 ) $ (501 ) — $ (72 ) Total assets as of September 30, 2018 $ 3,465 $ 6,699 $ 7,979 $ (6,693 ) $ 11,450 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 1 $ 740 $ (19 ) $ — $ 722 Retail (a) Generation (a) Corporate (a) Eliminations Total Three months ended September 30, 2017 (In millions) Operating revenues (a) $ 1,936 $ 1,313 $ — $ (509 ) $ 2,740 Depreciation and amortization 28 128 8 (1 ) 163 Reorganization costs 5 3 4 — 12 Equity in earnings of unconsolidated affiliates — 9 3 (3 ) 9 Income/(loss) from continuing operations before income taxes 72 272 (157 ) (1 ) 186 Income/(loss) from continuing operations 72 272 (158 ) (1 ) 185 Loss from discontinued operations, net of tax — — (22 ) — (22 ) Net Income/(Loss) 72 272 (180 ) (1 ) 163 Net Income/(Loss) attributable to NRG Energy, Inc. common stockholders $ 72 $ 256 $ (159 ) $ 2 $ 171 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 3 $ 493 $ 13 $ — $ 509 Retail (a) Generation (a) Corporate (a) Eliminations Total Nine months ended September 30, 2018 (In millions) Operating revenues (a) $ 5,497 $ 3,216 $ 10 $ (928 ) $ 7,795 Depreciation and amortization 86 259 25 — 370 Impairment losses — 74 — — 74 Reorganization costs 10 10 50 — — 70 Gain on sale of assets — 1 29 — 30 Equity in earnings of unconsolidated affiliates — 27 4 (5 ) 26 Loss on debt extinguishment, net — — (22 ) — (22 ) Income/(Loss) from continuing operations before income taxes 733 303 812 (1,228 ) 620 Income/(Loss) from continuing operations 733 302 794 (1,228 ) 601 Loss from discontinued operations, net of tax — — (320 ) — (320 ) Net Income/(Loss) 733 302 474 (1,228 ) 281 Net Income/(Loss) attributable to NRG Energy, Inc. common stockholders $ 732 $ 293 $ 479 $ (1,224 ) $ 280 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 7 $ 944 $ (23 ) $ — $ 928 Retail (a) Generation (a) Corporate (a) Eliminations Total Nine months ended September 30, 2017 Operating revenues (a) $ 4,868 $ 3,289 $ 13 $ (924 ) $ 7,246 Depreciation and amortization 81 385 26 (2 ) 490 Impairment losses — 60 — — 60 Reorganization costs 5 3 10 — — 18 Gain on sale of assets — 4 — — 4 Equity in (losses)/earnings of unconsolidated affiliates — (21 ) 6 (5 ) (20 ) Income/(loss) from continuing operations before income taxes 371 185 (433 ) (4 ) 119 Income/(loss) from continuing operations 380 183 (443 ) (4 ) 116 Loss from discontinued operations, net of tax — — (798 ) — (798 ) Net Income/(loss) 380 183 (1,241 ) (4 ) (682 ) Net Income/(loss) attributable to NRG Energy, Inc. common stockholders $ 380 $ 169 $ (1,169 ) $ 1 $ (619 ) (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 3 $ 872 $ 49 $ — $ 924

Earnings_(Loss) Per Share

Earnings/(Loss) Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings/(Loss) Per Share	Earnings/(Loss) Per Share Basic earnings/(loss) per common share is computed by dividing net income/(loss) by the weighted average number of common shares outstanding. Shares issued and treasury shares repurchased during the year are weighted for the portion of the year that they were outstanding. Diluted earnings/(loss) per share is computed in a manner consistent with that of basic income/(loss) per share while giving effect to all potentially dilutive common shares that were outstanding during the period. The reconciliation of NRG's basic and diluted loss per share is shown in the following table: Three months ended September 30, Nine months ended September 30, In millions, except per share data 2018 2017 2018 2017 Basic income/(loss) per share attributable to NRG Energy, Inc. common stockholders Net (loss)/income attributable to NRG Energy, Inc. common stockholders $ (72 ) $ 171 $ 280 $ (619 ) Weighted average number of common shares outstanding - basic 299 317 309 317 (Loss)/earnings per weighted average common share — basic $ (0.24 ) $ 0.54 $ 0.91 $ (1.95 ) Diluted income/(loss) per share attributable to NRG Energy, Inc. common stockholders Weighted average number of common shares outstanding - diluted 299 317 309 317 Incremental shares attributable to the issuance of equity compensation (treasury stock method) — 5 4 — Total dilutive shares 299 322 313 317 (Loss)/income per weighted average common share — diluted $ (0.24 ) $ 0.53 $ 0.89 $ (1.95 ) The following table summarizes NRG’s outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company’s diluted loss per share: Three months ended September 30, Nine months ended September 30, In millions of shares 2018 2017 2018 2017 Equity compensation plans 4 1 — 6 2048 Convertible Senior Notes 12 — 6 — Total 16 1 6 6

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Effective Tax Rate The income tax provision consisted of the following: Three months ended September 30, Nine months ended September 30, In millions, except rates 2018 2017 2018 2017 Income before income taxes $ 313 $ 186 $ 620 $ 119 Income tax expense from continuing operations 7 1 19 3 Effective tax rate 2.2 % 0.5 % 3.1 % 2.5 % For the three and nine months ended September 30, 2018 , and 2017, NRG's overall effective tax rate was different than the statutory rate of 21% and 35% , respectively primarily due to the tax benefit for the change in valuation allowance partially offset by current state tax expense. Uncertain Tax Benefits As of September 30, 2018 , NRG has recorded a non-current tax liability of $47 million for uncertain tax benefits from positions taken on various state income tax returns, including accrued interest. For the nine months ended September 30, 2018 , NRG accrued $2 million of interest relating to the uncertain tax benefits. As of September 30, 2018 , NRG had cumulative interest and penalties related to these uncertain tax benefits of $5 million . The Company recognizes interest and penalties related to uncertain tax benefits in income tax expense. NRG is subject to examination by taxing authorities for income tax returns filed in the U.S. federal jurisdiction and various state and foreign jurisdictions including operations located in Australia. The Company is no longer subject to U.S. federal income tax examinations for years prior to 2015. With few exceptions, state and local income tax examinations are no longer open for years before 2010.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 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 nine months ended September 30, 2018 , NRG recorded approximately $18 million and $53 million , respectively, under the transition services agreement against selling, general and administrative expenses post-Chapter 11 Filing. For the three and nine months ended September 30, 2017 , NRG recorded $14 million and $104 million , respectively related to these services. 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 September 30, 2018 and December 31, 2017 , $30 million and $92 million , respectively, of letters of credit were issued and outstanding under the NRG credit agreement for GenOn. As of September 30, 2018 , there were no loans outstanding under intercompany secured revolving credit facility. As of December 31, 2017 , there were $125 million , of loans outstanding under the intercompany secured revolving credit facility. The intercompany secured revolving credit facility contains customary covenants and events of default. As of September 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 September 30, 2018 . Interest continued to accrue during the pendency of the Chapter 11 Cases until July 2018, when all outstanding 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. As mentioned above, as of September 30, 2018, GenOn, GenMa, and REMA collectively had $30 million outstanding in letters of credit issued under the secured intercompany revolving credit agreement. In connection with the settlement between NRG and GenOn, GenOn, GenMA and REMA have provided support for those outstanding letters of credit through a back-to-back letter of credit and cash collateral. The outstanding letters of credit will continue to accrue any contractual fees and expenses until they are terminated. 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 September 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 September 30, 2018 and December 31, 2017 , the Company had $15 million and $32 million , respectively, of cash collateral posted in support of energy risk management activities by GenOn.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies This footnote should be read in conjunction with the complete description under Note 22 , Commitments and Contingencies , to the Company's 2017 Form 10-K. Commitments First Lien Structure — NRG has granted first liens to certain counterparties on a substantial portion of the Company's assets, excluding assets acquired in the GenOn and EME (including Midwest Generation) acquisitions, and NRG's assets that have project-level financing, to reduce the amount of cash collateral and letters of credit that it would otherwise be required to post from time to time to support its obligations under out-of-the-money hedge agreements for forward sales of power or MWh equivalents. The Company's lien counterparties may have a claim on NRG's assets to the extent market prices exceed the hedged price. As of September 30, 2018 , hedges under the first lien were in-the-money for NRG on a counterparty aggregate basis. Lignite Contract with Texas Westmoreland Coal Co. — The Company's Limestone facility historically blended lignite obtained from the Jewett mine, which was operated by Texas Westmoreland Coal Co, or TWCC, and coal sourced from the Powder River Basin in Wyoming. On August 18, 2016, NRG gave notice to TWCC terminating the active mining of lignite under the contract, effective on December 31, 2016. Under the contract, TWCC continues to be responsible for reclamation activities. NRG is responsible for reclamation costs and has recorded an adequate ARO liability. The Railroad Commission of Texas has imposed a bond obligation of $99 million on TWCC for the reclamation of the mine. Pursuant to the contract with TWCC, NRG supports this obligation through surety bonds. Additionally, NRG is obligated to provide additional performance assurance if required by the Railroad Commission of Texas. On October 9, 2018, TWCC and certain of its affiliates filed for protection under Chapter 11 of the U.S. Bankruptcy Code before the United States Bankruptcy Court for the Southern District of Texas. TWCC has obtained authorization from the bankruptcy court to continue to perform its obligations under its contract with the Company and to maintain surety bonds programs throughout its operations. In addition, NRG has not received any indication from the Railroad Commission of Texas of an intent to draw on the surety bonds. However, given the uncertainty involved in bankruptcy proceedings, it is uncertain whether and to what extent TWCC’s bankruptcy may in the future impact the reclamation costs incurred by NRG or the surety bonds. Contingencies The Company's material legal proceedings are described below. The Company believes that it has valid defenses to these legal proceedings and intends to defend them vigorously. NRG records reserves for estimated losses from contingencies when information available indicates that a loss is probable and the amount of the loss, or range of loss, can be reasonably estimated. As applicable, the Company has established an adequate reserve for the matters discussed below. In addition, legal costs are expensed as incurred. Management has assessed each of the following matters based on current information and made a judgment concerning its potential outcome, considering the nature of the claim, the amount and nature of damages sought, and the probability of success. Unless specified below, the Company is unable to predict the outcome of these legal proceedings or reasonably estimate the scope or amount of any associated costs and potential liabilities. As additional information becomes available, management adjusts its assessment and estimates of such contingencies accordingly. Because litigation is subject to inherent uncertainties and unfavorable rulings or developments, it is possible that the ultimate resolution of the Company's liabilities and contingencies could be at amounts that are different from its currently recorded reserves and that such difference could be material. In addition to the legal proceedings noted below, NRG and its subsidiaries are party to other litigation or legal proceedings arising in the ordinary course of business. In management's opinion, the disposition of these ordinary course matters will not materially adversely affect NRG's consolidated financial position, results of operations, or cash flows. Midwest Generation Asbestos Liabilities — The Company, through its subsidiary, Midwest Generation, may be subject to potential asbestos liabilities as a result of its acquisition of EME. The Company is currently analyzing the scope of potential liability as it may relate to Midwest Generation. The Company believes that it has established an adequate reserve for these cases. On March 27, 2018, ComEd filed a Motion to Compel Payments of Claims seeking $61 million related to asbestos liabilities. On April 25, 2018, NRG filed an Omnibus Objection to All Remaining Claims of ComEd and Exelon. A trial before the Bankruptcy Court to determine the amount of ComEd’s claims is currently scheduled for April 10, 2019. Telephone Consumer Protection Act Purported Class Actions — Three purported class action lawsuits have been filed against NRG Residential Solar Solutions, LLC — one in California and two in New Jersey. The plaintiffs generally allege misrepresentation by the call agents and violations of the TCPA, claiming that the defendants engaged in a telemarketing campaign placing unsolicited calls to individuals on the “Do Not Call List.” The plaintiffs seek statutory damages of up to $1,500 per plaintiff, actual damages and equitable relief. On June 22, 2017, plaintiffs in the California case filed a motion for leave to file a second amended complaint to substitute new plaintiffs. Defendants filed an opposition to this motion on June 26, 2017. The court granted plaintiffs' motion to substitute new plaintiffs and on August 1, 2017, defendants filed an answer to the second amended complaint. On August 31, 2017, the court in the California case agreed that the litigation should be stayed pending final court approval of the New Jersey settlement. On July 12, 2017, the parties in one of the New Jersey actions reached an agreement in principle to resolve the class allegations which was confirmed by a term sheet signed by the parties on July 28, 2017. On September 27, 2017, plaintiffs in one of the New Jersey cases filed their motion for preliminary approval of the class settlement which was approved by the court on November 17, 2017. On May 14, 2018, the court entered a final order approving the class action settlement and dismissing the lawsuit, thereby ending the New Jersey lawsuits. On July 2, 2018, the court in the California case entered an order dismissing the lawsuit. California Department of Water Resources and San Diego Gas & Electric Company v. Sunrise Power Company LLC — On January 29, 2016, CDWR and SDG&E filed a lawsuit against Sunrise Power Company, along with NRG and Chevron Power Corporation. In June 2001, CDWR and Sunrise entered into a 10 -year PPA under which Sunrise would construct and operate a generating facility and provide power to CDWR. At the time the PPA was entered into, Sunrise had a transportation services agreement, or TSA, to purchase natural gas from Kern River through April 30, 2018. In August 2003, CDWR entered into an agreement with Sunrise and Kern River in which CDWR accepted assignment of the TSA through the term of the PPA. After the PPA expired, Kern River demanded that any reassignment be to a party which met certain creditworthiness standards which Sunrise did not. As such, the plaintiffs brought this lawsuit against the defendants alleging breach of contract, breach of covenant of good faith and fair dealing and improper distributions. Plaintiffs generally claim damages of $1.2 million per month for the remaining 70 months of the TSA. On April 20, 2016, the defendants filed objections in response to the plaintiffs' complaint. The objections were granted on June 14, 2016; however, the plaintiffs were allowed to file amended complaints on July 1, 2016. On July 27, 2016, defendants filed objections to the amended complaints. On November 18, 2016, the court sustained the objections and allowed plaintiffs another opportunity to file a second amended lawsuit which they did on January 13, 2017. On April 21, 2017, the court issued an order sustaining the objections without leave to amend. On July 14, 2017, CDWR filed a notice of appeal. On January 10, 2018, CDWR filed its appellate brief. Defendants filed their opposition brief on April 10, 2018. On May 30, 2018, CDWR filed their reply brief. Griffoul v. NRG Residential Solar Solutions — On February 28, 2017, plaintiffs, consisting of New Jersey residential solar customers, filed a purported class action lawsuit in New Jersey state court. Plaintiffs allege violations of the New Jersey Consumer Fraud Action and Truth-in-Consumer Contracts, Warranty and Notice Act with regard to certain provisions of their residential solar contracts. The plaintiffs seek damages and injunctive relief as to the proper allocation of the solar renewable energy credits. On June 6, 2017, the defendants filed a motion to compel arbitration or dismiss the lawsuit. Plaintiffs filed their opposition on June 29, 2017. On July 14, 2017, the court denied NRG's motion to compel arbitration or dismiss the case. On July 25, 2017, NRG filed a motion for reconsideration of the appeal, which was denied. On August 22, 2017, NRG filed a notice of appeal. After oral argument on April 24, 2018, the Appellate Division reversed the lower court on May 4, 2018, and ordered that the plaintiff must arbitrate their claims against NRG. On May 23, 2018, the plaintiff filed a petition for certification with the Supreme Court of New Jersey seeking to overturn the Appellate Division ruling. The petition and objection are fully briefed. Rice v. NRG — On April 14, 2017, plaintiffs filed a purported class action lawsuit in the U.S. District Court for the Western District of Pennsylvania against NRG, First Energy Corporation and Matt Canastrale Contracting, Inc. Plaintiffs generally claim personal injury, trespass, nuisance and property damage related to the disposal of coal ash from GenOn's Elrama Power Plant and First Energy’s Mitchell and Hatfield Power Plants. Plaintiffs generally seek monetary damages, medical monitoring and remediation of their property. Plaintiffs filed an amended complaint on August 14, 2017. On October 20, 2017, NRG filed its answers and affirmative defenses. On July 6, 2018, NRG filed a motion for summary judgment. Plaintiffs filed their opposition to the motion for summary judgment on July 29, 2018. On September 7, 2018, the court granted NRG’s motion for summary judgment. Accordingly, NRG is no longer a party. Washington-St. Tammany and Claiborne Electric Cooperative v. LaGen — On June 28, 2017, plaintiffs Washington-St. Tammany Electric Cooperative, Inc. and Claiborne Electric Cooperative, Inc. filed a lawsuit against Louisiana Generating, L.L.C., or LaGen, in the United States District Court for the Middle District of Louisiana. The plaintiffs claim breach of contract against LaGen for allegedly improperly charging the plaintiffs for costs related to the installation and maintenance of certain pollution control technology. Plaintiffs seek damages for the alleged improper charges and a declaration as to which charges are proper under the contract. On September 14, 2017, the court issued a scheduling order setting this case for trial on October 21, 2019. LaGen filed its answer and affirmative defenses on November 17, 2017. GenOn Chapter 11 Cases — On June 14, 2017, the GenOn Entities filed voluntary petitions for relief under Chapter 11 of the Bankruptcy Code in the Bankruptcy Court. On December 12, 2017, the Bankruptcy Court entered an order confirming GenOn’s Chapter 11 plan, which provides for, among other things, GenOn’s transition to a standalone enterprise. GenOn’s Chapter 11 plan has not yet become effective and there can be no assurance that the effective date will occur. However, the NRG Settlement was approved by the Bankruptcy Court on December 12, 2017, and was consummated on July 16, 2018, resulting in the exchange of broad, mutual releases among the GenOn Entities, NRG and certain of their respective related parties. Upon the occurrence of the effective date of GenOn’s Chapter 11 plan, additional releases in favor of NRG will become operative and the GenOn Entities will no longer be subsidiaries of NRG. See Note 3 , Acquisitions, Discontinued Operations and Dispositions , for additional information related to the Chapter 11 Cases. BTEC v. NRG Texas Power — On July 18, 2017, BTEC New Albany LLC, or BTEC, filed a lawsuit against NRG Texas Power LLC, or NRG Texas Power, in the Harris County District Court in Texas. On January 15, 2013, the parties entered into a Membership Interest and Purchase Agreement, or MIPA, whereby BTEC agreed to dismantle, transport and rebuild an electric power generation facility at the former P.H. Robinson Electric Generating Station in Bacliff, Texas. The MIPA required BTEC to meet a Guaranteed Commercial Completion Date of May 31, 2016. Because BTEC had not satisfied all of the contractually-required acceptance criteria by the MIPA expiration date, NRG elected to terminate the contract in June 2017. BTEC claimed that NRG Texas Power breached the MIPA by improperly terminating it, and sought a declaratory judgment as to the rights and obligations of the parties as well as damages, interest and attorney’s fees. On September 7, 2017, NRG Texas Power filed a counterclaim seeking damages in excess of $48 million . On June 7, 2018, the parties resolved all claims and counterclaims in the lawsuit and a dismissal order was subsequently entered by the court on July 12, 2018. GenOn Related Contingencies Natural Gas Litigation — GenOn has been a party to several lawsuits, certain of which are class action lawsuits, in state and federal courts, of which four remain pending involving plaintiffs in Kansas, Missouri and Wisconsin. These lawsuits were filed in the aftermath of the California energy crisis in 2000 and 2001 and the resulting FERC investigations and relate to alleged conduct to increase natural gas prices in violation of state antitrust law and similar laws. The lawsuits seek treble or punitive damages, restitution and/or expenses. The lawsuits also name as parties a number of energy companies unaffiliated with NRG. In July 2011, the U.S. District Court for the District of Nevada, which was handling four of the five cases, granted the defendants' motion for summary judgment and dismissed all claims against GenOn in those cases. The plaintiffs appealed to the U.S. Court of Appeals for the Ninth Circuit, or the Ninth Circuit, which reversed the decision of the District Court. GenOn along with the other defendants in the lawsuit filed a petition for a writ of certiorari to the U.S. Supreme Court challenging the Ninth Circuit's decision and the U.S. Supreme Court granted the petition. On April 21, 2015, the U.S. Supreme Court affirmed the Ninth Circuit’s holding that plaintiffs’ state antitrust law claims are not field-preempted by the federal Natural Gas Act and the Supremacy Clause of the U.S. Constitution. The U.S. Supreme Court left open whether the claims were preempted on the basis of conflict preemption. The U.S. Supreme Court directed that the case be remanded to the U.S. District Court for the District of Nevada for further proceedings. On March 7, 2016, class plaintiffs filed their motions for class certification. On March 30, 2017, the court denied the plaintiffs' motions for class certification, which the plaintiffs appealed to. The plaintiffs petitioned the Ninth Circuit for interlocutory review. On July 12, 2018, the Ninth Circuit heard oral arguments and the case is under submission pending a decision. On February 26, 2018, GenOn filed objections to the proofs of claim filed in the Chapter 11 Cases by all of the plaintiffs in each of the four cases. GenOn filed that same day a motion asking the Bankruptcy Court to estimate all of the proofs of claim at zero dollars, to which the plaintiffs objected. The Bankruptcy Court denied the plaintiffs' objection, ruling that it had the authority to consider GenOn's objections to the proofs of claim and to estimate the claims, but has certified its decision for review by either the Fifth Circuit Court of Appeals or the District Court. In June 2018, GenOn reached a settlement with plaintiffs in three of the four remaining suits, which leaves only the one purported class action involving plaintiffs in Wisconsin. CenterPoint Energy Services is a defendant in that case, and GenOn has agreed to indemnify CenterPoint against certain losses relating to the lawsuit. The Nevada District Judge granted summary judgment in favor of CenterPoint in that lawsuit and the plaintiffs appealed that decision to the Ninth Circuit. The appeal was argued on February 16, 2018, and the case is under submission pending a decision. Potomac River Environmental Investigation — In March 2013, NRG Potomac River LLC, a subsidiary of GenOn, received notice that the District of Columbia Department of Environment (now renamed the Department of Energy and Environment, or DOEE) was investigating potential discharges to the Potomac River originating from the Potomac River Generating facility site, a site where the generation facility is no longer in operation. In connection with that investigation, DOEE served a civil subpoena on NRG Potomac River LLC requesting information related to the site and potential discharges occurring from the site. NRG Potomac River LLC provided various responsive materials. In January 2016, DOEE advised NRG Potomac River LLC that DOEE believed various environmental violations had occurred as a result of discharges DOEE believes occurred to the Potomac River from the Potomac River Generating facility site and as a result of associated failures to accurately or sufficiently report such discharges. DOEE has indicated it believes that penalties are appropriate in light of the violations. NRG Potomac River LLC is currently reviewing the information provided by DOEE. Natixis v. GenOn Mid-Atlantic — On February 16, 2018, Natixis Funding Corp. and Natixis, New York Branch filed a complaint in the Supreme Court of the State of New York against GenOn Mid-Atlantic, the owner lessors under GenOn Mid-Atlantic’s operating leases of the Dickerson and Morgantown coal generation units, and the lease indenture trustee under those leases. The plaintiffs’ allegations against GenOn Mid-Atlantic relate to a payment agreement between GenOn Mid-Atlantic and Natixis Funding Corp. to procure credit support for the payment of certain lease payments owed pursuant to the GenOn Mid-Atlantic operating leases for Morgantown and Dickerson. The plaintiffs seek approximately $34 million in damages arising from GenOn Mid-Atlantic’s purported breach of certain warranties in the payment agreement. On April 2, 2018, GenOn Mid-Atlantic removed the allegations against it to the U.S. District Court for the Southern District of New York. On April 11, 2018, the U.S. District Court for the Southern District of New York entered a briefing schedule on a forthcoming motion to remand by Natixis Funding Corp. and a forthcoming motion to transfer by GenOn Mid-Atlantic. On April 26, 2018, Natixis Funding Corp. filed its motion to remand. On May 31, 2018, GenOn Mid-Atlantic opposed the motion to remand and filed a cross-motion to transfer. The parties completed briefing on the motions to remand and transfer on July 9, 2018, and the U.S. District Court for the Southern District of New York held an oral argument on July 18, 2018 and continued the motions to a subsequent conference scheduled for September 26, 2018. In the state court action, the court has scheduled oral argument for September 25, 2018, on the owner lessors' dispositive motions. Cheswick NPDES Permit Appeal — On September 24, 2018, Sierra Club and Three Rivers Waterkeeper filed an appeal challenging the NPDES permit that was issued to GenOn’s Cheswick power plant in July 2018. The appeal seeks, among other remedies, a hearing, a declaration that the permit is unlawful and inappropriate, and for an order remanding the permit to Pennsylvania’s Department of Environment to modify the permit to remedy the flaws about which the appellants complain. The parties are discussing a hearing scheduling order. New Jersey Department of Environmental Protection Notice of Violation — On May 31, 2018, REMA (as successor-in-interest to Reliant Energy NJ Holdings) was issued a notice of violation by the New Jersey Department of Environmental Protection for alleged violations of the New Jersey Spill Compensation and Control Act (N.J.S.A. 58: 10-23 et seq.) at the Atlantic Substation property in Colts Neck Township, New Jersey. These alleged violations remain under review by REMA.

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2018
Regulatory Matters Disclosure [Abstract]
Regulatory Matters	Regulatory Matters This footnote should be read in conjunction with the complete description under Note 23 , Regulatory Matters , to the Company's 2017 Form 10-K. Environmental regulatory matters are discussed within Note 17 , Environmental Matters , to this Form 10-Q . NRG operates in a highly regulated industry and is subject to regulation by various federal and state agencies. As such, NRG is affected by regulatory developments at both the federal and state levels and in the regions in which NRG operates. In addition, NRG is subject to the market rules, procedures, and protocols of the various ISO and RTO markets in which NRG participates. These power markets are subject to ongoing legislative and regulatory changes that may impact NRG's wholesale and retail businesses. In addition to the regulatory proceedings noted below, NRG and its subsidiaries are parties to other regulatory proceedings arising in the ordinary course of business or have other regulatory exposure. In management's opinion, the disposition of these ordinary course matters will not materially adversely affect NRG's consolidated financial position, results of operations, or cash flows. National Zero-Emission Credits for Nuclear Plants in Illinois — In 2016, Illinois enacted a Zero Emission Credit, or ZEC, program for selected nuclear units in Illinois. In total, the program directs over $2.5 billion over ten years to two Exelon-owned nuclear power plants in Illinois. These ZECs are out-of-market subsidies that threaten to artificially suppress market prices and interfere with the wholesale power market. On February 14, 2017, NRG, along with other companies, filed a complaint in the U.S. District Court for the Northern District of Illinois alleging that the state program is preempted by federal law and in violation of the dormant commerce clause. On July 14, 2017, Defendants' motions to dismiss were granted. On July 17, 2017, NRG, along with other companies, filed a notice of appeal to the U.S. Court of Appeals for the Seventh Circuit. On September 13, 2018, the U.S. Court of Appeals for the Seventh Circuit affirmed the District Court’s decision to dismiss the complaint. On September 27, 2018, NRG, along with other companies, filed a Petition for a Panel Rehearing with the Seventh Circuit. On October 9, 2018, the Seventh Circuit denied the rehearing. Zero-Emission Credits for Nuclear Plants in New York — On August 1, 2016, the NYSPSC issued its Clean Energy Standard, or CES, which provided for ZECs which would provide more than $7.6 billion over 12 years in out-of-market subsidy payments to certain selected nuclear generating units in the state. These ZECs are out-of-market subsidies that threaten to artificially suppress market prices and interfere with the wholesale power market. On October 19, 2016, NRG, along with other companies, filed a complaint in the U.S. District Court for the Southern District of New York, challenging the validity of the NYSPSC action and the ZEC program. On July 25, 2017, Defendants' motions to dismiss were granted. On August 24, 2017, NRG, along with other plaintiff companies, filed a notice of appeal to the U.S. Court of Appeals for the Second Circuit. On September 27, 2018, the Second Circuit affirmed the decision of the District Court. Department of Energy's Proposed Grid Resiliency Pricing Rule and Subsequent FERC Proceeding — On September 29, 2017, the Department of Energy issued a proposed rulemaking titled the "Grid Resiliency Pricing Rule." The rulemaking directs FERC to take action to reform the ISO/RTO markets to value certain reliability and resiliency attributes of electric generation resources. On October 2, 2017, FERC issued a notice inviting comments. On October 4, 2017, FERC staff issued a series of questions requesting commenters to address. On October 23, 2017, NRG filed comments encouraging FERC to act expeditiously to modernize energy and capacity markets in a manner compatible with robust competitive markets. On January 8, 2018, FERC terminated the proposed rulemaking and opened a new proceeding asking each ISO/RTO to address specific questions focused on grid resilience. On March 9, 2018, the ISOs/RTOs filed comments to the questions posed by FERC. The Company responded on May 9, 2018 and is currently awaiting a decision from FERC.

Environmental Matters

Environmental Matters	9 Months Ended
	Sep. 30, 2018
Environmental Matters Disclosure [Abstract]
Environmental Matters	Environmental Matters This footnote should be read in conjunction with the complete description under Note 24 , Environmental Matters , to the Company's 2017 Form 10-K. NRG is subject to a wide range of environmental laws in the development, construction, ownership and operation of projects. These laws generally require that governmental permits and approvals be obtained before construction and during operation of power plants. NRG is also subject to laws regarding the protection of wildlife, including migratory birds, eagles and threatened and endangered species. The electric generation industry has been facing requirements regarding GHGs, combustion byproducts, water discharge and use, and threatened and endangered species that have been put in place in recent years. However, under the current U.S. presidential administration, some of these rules are being reconsidered and reviewed. In general, future laws are expected to require the addition of emissions controls or other environmental controls or to impose certain restrictions on the operations of the Company's facilities, which could have a material effect on the Company's consolidated financial position, results of operations, or cash flows. Federal and state environmental laws generally have become more stringent over time, although this trend could slow in the near term with respect to federal laws under the current U.S. presidential administration. Air On August 31, 2018, EPA proposed replacing the Clean Power Plan (CPP) rule, which sought to broadly regulate CO2 emissions from the power sector, with the Affordable Clean Energy (ACE) rule, which if finalized, would require states to develop plans to seek heat rate improvements from coal-fired EGUs. The Company believes that the ACE rule replacing the CPP rule would on balance be positive for its generation fleet. The EPA finalized CSAPR in 2011, which was intended to replace CAIR in January 2012, to address certain states' obligations to reduce emissions so that downwind states can achieve federal air quality standards. In December 2011, the D.C. Circuit stayed the implementation of CSAPR and then vacated CSAPR in August 2012 but kept CAIR in place until the EPA could replace it. In April 2014, the U.S. Supreme Court reversed and remanded the D.C. Circuit's decision. In October 2014, the D.C. Circuit lifted the stay of CSAPR. In response, the EPA in November 2014 amended the CSAPR compliance dates. Accordingly, CSAPR replaced CAIR on January 1, 2015. On July 28, 2015, the D.C. Circuit held that the EPA had exceeded its authority by requiring certain reductions that were not necessary for downwind states to achieve federal standards. Although the D.C. Circuit kept the rule in place, the court ordered the EPA to revise the Phase 2 (or 2017) (i) SO 2 budgets for four states including Texas and (ii) ozone-season NOx budgets for 11 states including Maryland, New Jersey, New York, Ohio, Pennsylvania and Texas. On October 26, 2016, the EPA finalized the CSAPR Update Rule, which reduces future NOx allocations and discounts the current banked allowances to account for the more stringent 2008 Ozone NAAQS and to address the D.C. Circuit's July 2015 decision. This rule has been challenged in the D.C. Circuit. The Company believes its investment in pollution controls and cleaner technologies leave the fleet well-positioned for compliance. In February 2012, the EPA promulgated standards (the MATS rule) to control emissions of HAPs from coal and oil-fired electric generating units. The rule established limits for mercury, non-mercury metals, certain organics and acid gases, which had to be met beginning in April 2015 (with some units getting a 1-year extension). In June 2015, the U.S. Supreme Court issued a decision in the case of Michigan v. EPA, and held that the EPA unreasonably refused to consider costs when it determined that it was "appropriate and necessary" to regulate HAPs emitted by electric generating units. The U.S. Supreme Court did not vacate the MATS rule but rather remanded it to the D.C. Circuit for further proceedings. In December 2015, the D.C. Circuit remanded the MATS rule to the EPA without vacatur. On April 25, 2016, the EPA released a supplemental finding that the benefits of this regulation outweigh the costs to address the U.S. Supreme Court's ruling that the EPA had not properly considered costs. This finding has been challenged in the D.C. Circuit. On April 18, 2017, the EPA asked the D.C. Circuit to postpone oral argument that had been scheduled for May 18, 2017 because the EPA is closely reviewing the supplemental finding to determine whether it should reconsider all or part of the rule. On April 27, 2017, the D.C. Circuit granted EPA's request to postpone the oral argument and hold the case in abeyance. While NRG cannot predict the final outcome of this rulemaking, NRG believes that because it has already invested in pollution controls and cleaner technologies, the fleet is well-positioned to comply with the MATS rule. Water In August 2014, the EPA finalized the regulation regarding the use of water for once through cooling at existing facilities to address impingement and entrainment concerns. NRG anticipates that more stringent requirements will be incorporated into some of its water discharge permits over the next several years as NPDES permits are renewed. Effluent Limitations Guidelines — In November 2015, the EPA revised the Effluent Limitations Guidelines for Steam Electric Generating Facilities, which would have imposed more stringent requirements (as individual permits were renewed) for wastewater streams from flue gas desulfurization, or FGD, fly ash, bottom ash, and flue gas mercury control. In April 2017, the EPA granted two petitions to reconsider the rule and also administratively stayed some of the deadlines. On September 18, 2017, the EPA promulgated a final rule that (i) postpones the compliance dates to preserve the status quo for FGD wastewater and bottom ash transport water by two years to November 2020 until the EPA completes its next rulemaking and (ii) withdrew the April 2017 administrative stay. The legal challenges have been suspended while the EPA reconsiders and likely modifies the rule. Accordingly, the Company has largely eliminated its estimate of the environmental capital expenditures that would have been required to comply with permits incorporating the revised guidelines. The Company will revisit these estimates after the rule is revised. Byproducts, Wastes, Hazardous Materials and Contamination In April 2015, the EPA finalized the rule regulating byproducts of coal combustion (e.g., ash and gypsum) as solid wastes under the RCRA. In 2017, the EPA agreed to reconsider the rule. On July 30, 2018, the EPA promulgated a rule that amends the existing ash rule by extending some of the deadlines and providing more flexibility for compliance. On August 21, 2018, the DC Circuit found, among other things, that EPA had not adequately regulated unlined ponds and legacy ponds. Accordingly, we anticipate that EPA will promulgate new regulations to address these issues (including compliance deadlines) as it reconsiders other aspects of the existing rule. The EPA has stated that it intends to further revise the rule. East/West New Source Review — The EPA and various states have been investigating compliance of electric generating facilities with the pre-construction permitting requirements of the CAA known as “new source review,” or NSR. In 2007, Midwest Generation received an NOV from the EPA alleging that past work at Crawford, Fisk, Joliet, Powerton, Waukegan and Will County generating stations violated NSR and other regulations. These alleged violations are the subject of litigation described in Note 15 , Commitments and Contingencies . Additionally, in April 2013, the Connecticut Department of Energy and Environmental Protection issued four NOVs alleging that past work at oil-fired combustion turbines at the Torrington Terminal, Franklin, Branford and Middletown generating stations violated regulations regarding NSR.

Condensed Consolidating Financi

Condensed Consolidating Financial Information	9 Months Ended
	Sep. 30, 2018
Condensed Consolidating Financial Information Disclosure [Abstract]
Condensed Consolidating Financial Information	Condensed Consolidating Financial Information As of September 30, 2018 , the Company had outstanding $4.8 billion of Senior Notes due from 2022 to 2048, as shown in Note 8 , Debt and Capital Leases . These Senior Notes are guaranteed by certain of NRG's current and future 100% owned domestic subsidiaries, or guarantor subsidiaries. These guarantees are both joint and several. The non-guarantor subsidiaries include all of NRG's foreign subsidiaries and certain domestic subsidiaries. Unless otherwise noted below, each of the following guarantor subsidiaries fully and unconditionally guaranteed the Senior Notes as of September 30, 2018 : Ace Energy, Inc. NRG Advisory Services LLC NRG Norwalk Harbor Operations Inc. Allied Home Warranty GP LLC NRG Affiliate Services Inc. NRG Operating Services, Inc. Allied Warranty LLC NRG Arthur Kill Operations Inc. NRG Oswego Harbor Power Operations Inc. Arthur Kill Power LLC NRG Astoria Gas Turbine Operations Inc. NRG PacGen Inc. Astoria Gas Turbine Power LLC NRG Bayou Cove LLC NRG Portable Power LLC Bayou Cove Peaking Power, LLC NRG Business Services LLC NRG Power Marketing LLC BidURenergy, Inc. NRG Cabrillo Power Operations Inc. NRG Reliability Solutions LLC Cabrillo Power I LLC NRG California Peaker Operations LLC NRG Renter's Protection LLC Cabrillo Power II LLC NRG Cedar Bayou Development Company, LLC NRG Retail LLC Carbon Management Solutions LLC NRG Connected Home LLC NRG Retail Northeast LLC Cirro Group, Inc. NRG Connecticut Affiliate Services Inc. NRG Rockford Acquisition LLC Cirro Energy Services, Inc. NRG Construction LLC NRG Saguaro Operations Inc. Connecticut Jet Power LLC NRG Curtailment Solutions, Inc NRG Security LLC Cottonwood Development LLC NRG Development Company Inc. NRG Services Corporation Cottonwood Energy Company LP NRG Devon Operations Inc. NRG SimplySmart Solutions LLC Cottonwood Generating Partners I LLC NRG Dispatch Services LLC NRG South Central Affiliate Services Inc. Cottonwood Generating Partners II LLC NRG Distributed Energy Resources Holdings LLC NRG South Central Generating LLC Cottonwood Generating Partners III LLC NRG Distributed Generation PR LLC NRG South Central Operations Inc. Cottonwood Technology Partners LP NRG Dunkirk Operations Inc. NRG South Texas LP Devon Power LLC NRG El Segundo Operations Inc. NRG Texas C&I Supply LLC Dunkirk Power LLC NRG Energy Efficiency-L LLC NRG Texas Gregory LLC Eastern Sierra Energy Company LLC NRG Energy Labor Services LLC NRG Texas Holding Inc. El Segundo Power, LLC NRG ECOKAP Holdings LLC NRG Texas LLC El Segundo Power II LLC NRG Energy Services Group LLC NRG Texas Power LLC Energy Alternatives Wholesale, LLC NRG Energy Services International Inc. NRG Warranty Services LLC Energy Choice Solutions LLC NRG Energy Services LLC NRG West Coast LLC Energy Plus Holdings LLC NRG Generation Holdings, Inc. NRG Western Affiliate Services Inc. Energy Plus Natural Gas LLC NRG Greenco LLC O'Brien Cogeneration, Inc. II Energy Protection Insurance Company NRG Home & Business Solutions LLC ONSITE Energy, Inc. Everything Energy LLC NRG Home Services LLC Oswego Harbor Power LLC Forward Home Security, LLC NRG Home Solutions LLC Reliant Energy Northeast LLC GCP Funding Company, LLC NRG Home Solutions Product LLC Reliant Energy Power Supply, LLC Green Mountain Energy Company NRG Homer City Services LLC Reliant Energy Retail Holdings, LLC Gregory Partners, LLC NRG Huntley Operations Inc. Reliant Energy Retail Services, LLC Gregory Power Partners LLC NRG HQ DG LLC RERH Holdings, LLC Huntley Power LLC NRG Identity Protect LLC Saguaro Power LLC Independence Energy Alliance LLC NRG Ilion Limited Partnership Somerset Operations Inc. Independence Energy Group LLC NRG Ilion LP LLC Somerset Power LLC Independence Energy Natural Gas LLC NRG International LLC Texas Genco GP, LLC Indian River Operations Inc. NRG Maintenance Services LLC Texas Genco Holdings, Inc. Indian River Power LLC NRG Mextrans Inc. Texas Genco LP, LLC Louisiana Generating LLC NRG MidAtlantic Affiliate Services Inc. Texas Genco Services, LP Meriden Gas Turbines LLC NRG Middletown Operations Inc. US Retailers LLC Middletown Power LLC NRG Montville Operations Inc. Vienna Operations Inc. Montville Power LLC NRG New Roads Holdings LLC Vienna Power LLC NEO Corporation NRG North Central Operations Inc. WCP (Generation) Holdings LLC New Genco GP, LLC NRG Northeast Affiliate Services Inc. West Coast Power LLC Norwalk Power LLC NRG conducts much of its business through and derives much of its income from its subsidiaries. Therefore, the Company's ability to make required payments with respect to its indebtedness and other obligations depends on the financial results and condition of its subsidiaries and NRG's ability to receive funds from its subsidiaries. There are no restrictions on the ability of any of the guarantor subsidiaries to transfer funds to NRG. However, there may be restrictions for certain non-guarantor subsidiaries. The following condensed consolidating financial information presents the financial information of NRG Energy, Inc., the guarantor subsidiaries and the non-guarantor subsidiaries in accordance with Rule 3-10 under the SEC Regulation S-X. The financial information may not necessarily be indicative of results of operations or financial position had the guarantor subsidiaries or non-guarantor subsidiaries operated as independent entities. In this presentation, NRG Energy, Inc. consists of parent company operations. Guarantor subsidiaries and non-guarantor subsidiaries of NRG are reported on an equity basis. For companies acquired, the fair values of the assets and liabilities acquired have been presented on a push-down accounting basis. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 2,618 $ 445 $ — $ (2 ) $ 3,061 Operating Costs and Expenses Cost of operations 2,005 295 9 (2 ) 2,307 Depreciation and amortization 67 36 9 — 112 Impairment losses — — — — — Selling, general and administrative 125 21 139 (73 ) 212 Reorganization costs — — 27 — 27 Development costs — (2 ) 3 — 1 Total operating costs and expenses 2,197 350 187 (75 ) 2,659 Gain on sale of assets — 14 — — 14 Operating Income/(Loss) 421 109 (187 ) 73 416 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 6 — 466 (472 ) — Equity in earnings of unconsolidated affiliates — 20 — — 20 Other income/(expense), net 4 8 5 — 17 Loss on debt extinguishment, net — (19 ) — (19 ) Interest expense (3 ) (8 ) (110 ) — (121 ) Total other income/(expense) 7 20 342 (472 ) (103 ) Income from Continuing Operations Before Income Taxes 428 129 155 (399 ) 313 Income tax expense/(benefit) 122 41 (156 ) — 7 Income from Continuing Operations 306 88 311 (399 ) 306 Income/(loss) from discontinued operations, net of income tax — 17 (371 ) — (354 ) Net Income/(Loss) 306 105 (60 ) (399 ) (48 ) Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests — (61 ) 12 73 24 Net Income/(Loss) Attributable to NRG Energy, Inc. common stockholders $ 306 $ 166 $ (72 ) $ (472 ) $ (72 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the nine months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 6,736 $ 1,072 $ — $ (13 ) $ 7,795 Operating Costs and Expenses Cost of operations 5,006 719 18 (13 ) 5,730 Depreciation and amortization 216 129 25 — 370 Impairment losses — 74 — — 74 Selling, general and administrative 337 46 282 (74 ) 591 Reorganization costs 4 — 66 — 70 Development costs — — 10 (1 ) 9 Total operating costs and expenses 5,563 968 401 (88 ) 6,844 Gain on sale of assets 3 27 — — 30 Operating Income/(Loss) 1,176 131 (401 ) 75 981 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 14 — 1,156 (1,170 ) — Equity in earnings/(losses) of unconsolidated affiliates — 27 (1 ) — 26 Other income/(expense), net 13 (27 ) 10 — (4 ) Loss on debt extinguishment, net — — (22 ) — (22 ) Interest expense (11 ) (42 ) (308 ) — (361 ) Total other income/(expense) 16 (42 ) 835 (1,170 ) (361 ) Income from Continuing Operations Before Income Taxes 1,192 89 434 (1,095 ) 620 Income tax expense/(benefit) 343 26 (350 ) — 19 Income from Continuing Operations 849 63 784 (1,095 ) 601 Income/(loss) from discontinued operations, net of income tax — 77 (397 ) — (320 ) Net Income 849 140 387 (1,095 ) 281 Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests — (181 ) 107 75 1 Net Income Attributable to NRG Energy, Inc. $ 849 $ 321 $ 280 $ (1,170 ) $ 280 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) For the three months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income $ 306 $ 105 $ (60 ) $ (399 ) $ (48 ) Other Comprehensive Income/(Loss), net of tax Unrealized gain/(loss) on derivatives, net — 10 (13 ) 7 4 Foreign currency translation adjustments, net (2 ) (2 ) (1 ) 3 (2 ) Defined benefit plans, net — — (1 ) — (1 ) Other comprehensive (loss)/income (2 ) 8 (15 ) 10 1 Comprehensive Income/(Loss) 304 113 (75 ) (389 ) (47 ) Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (58 ) 11 73 26 Comprehensive Income/(Loss) Attributable to NRG Energy, Inc. common stockholders $ 304 $ 171 $ (86 ) $ (462 ) $ (73 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME For the nine months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net income $ 849 $ 140 $ 387 $ (1,095 ) $ 281 Other comprehensive (loss)/income, net of tax Unrealized gain on derivatives, net — 30 9 (15 ) 24 Foreign currency translation adjustments, net (8 ) (8 ) (9 ) 17 (8 ) Available-for-sale securities, net — — 1 — 1 Defined benefit plans, net — — (3 ) — (3 ) Other comprehensive (loss)/income (8 ) 22 (2 ) 2 14 Comprehensive income 841 162 385 (1,093 ) 295 Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (167 ) 107 75 15 Comprehensive income attributable to NRG Energy, Inc. $ 841 $ 329 $ 278 $ (1,168 ) $ 280 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated ASSETS (In millions) Current Assets Cash and cash equivalents $ 130 $ 22 $ 1,207 $ — $ 1,359 Funds deposited by counterparties 30 — — — 30 Restricted cash 5 15 8 — 28 Accounts receivable, net 1,151 97 49 — 1,297 Inventory 301 107 — — 408 Derivative instruments 687 24 17 (45 ) 683 Deferred income tax 38 80 (118 ) — — Cash collateral paid in support of energy risk management activities 194 15 — — 209 Accounts receivable - affiliate 458 55 762 (1,256 ) 19 Prepayments and other current assets 160 35 53 — 248 Current assets - discontinued operations — 4 — — 4 Total current assets 3,154 454 1,978 (1,301 ) 4,285 Property, plant and equipment, net 2,372 1,077 150 — 3,599 Other Assets Investment in subsidiaries 477 — 4,379 (4,856 ) — Equity investments in affiliates — 452 — — 452 Notes receivable, less current portion — 10 12 (12 ) 10 Goodwill 359 180 — — 539 Intangible assets, net 403 199 — — 602 Nuclear decommissioning trust fund 719 — — — 719 Derivative instruments 357 9 36 (10 ) 392 Deferred income tax 34 (149 ) 126 — 11 Other non-current assets 92 70 119 — 281 Non-current assets - discontinued operations — 560 — — 560 Total other assets 2,441 1,331 4,672 (4,878 ) 3,566 Total Assets $ 7,967 $ 2,862 $ 6,800 $ (6,179 ) $ 11,450 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 89 $ 504 $ — $ 593 Accounts payable 705 55 64 — 824 Accounts payable — affiliate 1,610 (191 ) (148 ) (1,257 ) 14 Derivative instruments 565 30 — (45 ) 550 Deferred income taxes — 1 (1 ) — — Cash collateral received in support of energy risk management activities 30 — — — 30 Accrued expenses and other current liabilities 282 40 337 — 659 Accrued expenses and other current liabilities-affiliate — — 1 — 1 Current liabilities - discontinued operations — 52 — — 52 Total current liabilities 3,192 76 757 (1,302 ) 2,723 Other Liabilities Long-term debt and capital leases 244 244 6,182 (12 ) 6,658 Nuclear decommissioning reserve 278 — — — 278 Nuclear decommissioning trust liability 432 — — — 432 Deferred income taxes 112 62 (156 ) — 18 Derivative instruments 361 6 — (10 ) 357 Out-of-market contracts, net 54 123 — — 177 Other non-current liabilities 410 197 570 — 1,177 Non-current liabilities - discontinued operations — 547 — — 547 Total non-current liabilities 1,891 1,179 6,596 (22 ) 9,644 Total liabilities 5,083 1,255 7,353 (1,324 ) 12,367 Redeemable noncontrolling interest in subsidiaries — 19 — — 19 Stockholders’ Equity 2,884 1,588 (553 ) (4,855 ) (936 ) Total Liabilities and Stockholders’ Equity $ 7,967 $ 2,862 $ 6,800 $ (6,179 ) $ 11,450 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the nine months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income $ 849 $ 140 $ 387 $ (1,095 ) $ 281 Loss from discontinued operations — 77 (397 ) — (320 ) Income from continuing operations 849 63 784 (1,095 ) 601 Adjustments to reconcile net income to net cash provided/(used) by operating activities: Distributions and equity in earnings of unconsolidated affiliates — 9 1 — 10 Depreciation, amortization and accretion 240 138 25 — 403 Provision for bad debts 55 2 — — 57 Amortization of nuclear fuel 38 — — — 38 Amortization of financing costs and debt discount/premiums — 5 16 — 21 Adjustment for debt extinguishment — — 22 — 22 Amortization of intangibles and out-of-market contracts 15 6 — — 21 Amortization of unearned equity compensation — — 36 — 36 Impairment losses — 89 — — 89 Changes in deferred income taxes and liability for uncertain tax benefits 343 11 (360 ) — (6 ) Changes in nuclear decommissioning trust liability 50 — — — 50 Changes in derivative instruments (38 ) 40 (4 ) (15 ) (17 ) Changes in collateral deposits in support of energy risk management activities (16 ) (14 ) — — (30 ) Gain on sale of emission allowances (20 ) — — — (20 ) Gain on sale of assets (3 ) (27 ) — — (30 ) GenOn settlement in July 2018 — — (125 ) — (125 ) Loss on deconsolidation of business — 13 — — 13 Changes in other working capital (567 ) (61 ) (857 ) 1,110 (375 ) Cash provided/(used) by continuing operations 946 274 (462 ) — 758 Cash provided by discontinued operations — 324 — — 324 Net Cash Provided/(Used) by Operating Activities 946 598 (462 ) — 1,082 Cash Flows from Investing Activities Acquisition of business, net of cash acquired (2 ) (207 ) — — (209 ) Capital expenditures (158 ) (150 ) — (37 ) — (345 ) Purchases of emission allowances (30 ) — — — (30 ) Proceeds from sale of emission allowances 54 — — — 54 Investments in nuclear decommissioning trust fund securities (449 ) — — — (449 ) Proceeds from the sale of nuclear decommissioning trust fund securities 398 — — — 398 Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees 10 8 1,537 — 1,555 Deconsolidation of business — (268 ) — — (268 ) Change in investments in unconsolidated affiliates — (62 ) — — (62 ) Cash (used)/provided by continuing operations (177 ) (679 ) 1,500 — 644 Cash used by discontinued operations — (703 ) (703 ) Net Cash (Used)/Provided by Investing Activities (177 ) (1,382 ) 1,500 — (59 ) Cash Flows from Financing Activities Payments (for)/from intercompany loans (645 ) (12 ) 657 — — Payment of dividends to common stockholders — — (28 ) — (28 ) Payment for treasury stock — — (1,000 ) — (1,000 ) Proceeds from issuance of long-term debt — 163 832 — 995 Payments for short and long-term debt — (106 ) (864 ) — (970 ) Receivable from affiliate — — (26 ) (26 ) Net distributions to noncontrolling interests in subsidiaries — (17 ) — — (17 ) Payment of debt issuance costs — — (19 ) — (19 ) Other — (4 ) — — (4 ) Cash provided/(used) by continuing operations (645 ) 24 (448 ) — (1,069 ) Cash provided by discontinued operations — 403 — — 403 Net Cash Provided/(Used) by Financing Activities (645 ) 427 (448 ) — (666 ) Effect of exchange rate changes on cash and cash equivalents — 1 — — 1 Change in cash from discontinued operations — 24 — — 24 Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash 124 (380 ) 590 — 334 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 41 399 643 — 1,083 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 165 $ 19 $ 1,233 $ — $ 1,417 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 2,366 $ 386 $ — $ (12 ) $ 2,740 Operating Costs and Expenses Cost of operations 1,826 239 18 (11 ) 2,072 Depreciation and amortization 100 55 8 — 163 Selling, general and administrative 106 16 69 (1 ) 190 Reorganization costs 2 (7 ) 17 — 12 Development costs — 1 5 — 6 Total operating costs and expenses 2,034 304 117 (12 ) 2,443 Operating Income/(Loss) 332 82 (117 ) — 297 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 7 — 459 (466 ) — Equity in earnings/(losses) of unconsolidated affiliates — 10 (1 ) — 9 Other income, net 7 38 8 (34 ) 19 Interest expense (4 ) (21 ) (114 ) — (139 ) Total other income/(expense) 10 27 352 (500 ) (111 ) Income from Continuing Operations Before Income Taxes 342 109 235 (500 ) 186 Income tax expense — — 1 — 1 Income from Continuing Operations 342 109 234 (500 ) 185 Income/(loss) from discontinued operations, net of income tax — 12 (34 ) — (22 ) Net Income 342 121 200 (500 ) 163 Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (3 ) 29 (34 ) (8 ) Net Income Attributable to NRG Energy, Inc. common stockholders $ 342 $ 124 $ 171 $ (466 ) $ 171 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the nine months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 6,241 $ 1,042 $ — $ (37 ) $ 7,246 Operating Costs and Expenses Cost of operations 4,872 697 56 (36 ) 5,589 Depreciation and amortization 299 167 24 — — 490 Impairment losses 42 18 — — 60 Selling, general and administrative 309 55 — 271 (1 ) 634 Reorganization costs 2 (1 ) 17 — 18 Development costs — 4 14 — 18 Total operating costs and expenses 5,524 940 382 (37 ) 6,809 Other income - affiliate — — 87 — 87 Gain on sale of assets 4 — — — 4 Operating Income/(Loss) 721 102 (295 ) — 528 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 20 — 738 (758 ) — Equity in (losses) of unconsolidated affiliates — (17 ) (3 ) — (20 ) Other income, net 7 82 23 (69 ) 43 Interest expense (11 ) (68 ) (353 ) — (432 ) Total other income/(expense) 16 (3 ) 405 (827 ) (409 ) Income from Continuing Operations Before Income Taxes 737 99 110 (827 ) 119 Income tax (benefit)/expense — (7 ) 10 — 3 Income from Continuing Operations 737 106 100 (827 ) 116 Loss from discontinued operations, net of income tax — (134 ) (664 ) — (798 ) Net Income/(Loss) 737 (28 ) (564 ) (827 ) (682 ) Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (49 ) 55 (69 ) (63 ) Net Income/(Loss) Attributable to NRG Energy, Inc. $ 737 $ 21 $ (619 ) $ (758 ) $ (619 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME For the three months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income $ 342 $ 121 $ 200 $ (500 ) $ 163 Other Comprehensive Income, net of tax Unrealized gain on derivatives, net 52 58 6 (109 ) 7 Foreign currency translation adjustments, net 1 1 4 (4 ) 2 Available-for-sale securities, net — — 1 — 1 Defined benefit plans, net 10 10 (1 ) (20 ) (1 ) Other comprehensive income 63 69 10 (133 ) 9 Comprehensive Income 405 190 210 (633 ) 172 Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (3 ) 32 (34 ) (5 ) Comprehensive Income Attributable to NRG Energy, Inc. common stockholders $ 405 $ 193 $ 178 $ (599 ) $ 177 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) For the nine months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. Eliminations (a) Consolidated (In millions) Net income/(loss) $ 737 $ (28 ) $ (564 ) $ (827 ) $ (682 ) Other comprehensive income/(loss), net of tax Unrealized gain on derivatives, net 52 57 7 (109 ) 7 Foreign currency translation adjustments, net 6 6 10 (13 ) 9 Available-for-sale securities, net — — 2 — 2 Defined benefit plans, net 10 39 25 (49 ) 25 Other comprehensive income 68 102 44 (171 ) 43 Comprehensive income/(loss) 805 74 (520 ) (998 ) (639 ) Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (49 ) 57 (69 ) (61 ) Comprehensive income/(loss) Attributable to NRG Energy, Inc. $ 805 $ 123 $ (577 ) $ (929 ) $ (578 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS December 31, 2017 Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (b) ASSETS (In millions) Current Assets Cash and cash equivalents $ — $ 124 $ 643 $ — $ 767 Funds deposited by counterparties 37 — — — 37 Restricted cash 4 275 — — 279 Accounts receivable, net 911 45 4 — 960 Inventory 338 148 — — 486 Derivative instruments 646 26 9 (57 ) 624 Cash collateral paid in support of energy risk management activities 170 1 — — 171 Accounts receivable - affiliate 685 183 (148 ) (534 ) 186 Prepayments and other current assets 122 30 27 — 179 Current assets held-for-sale 8 108 — — 116 Current assets - discontinued operations — 705 — — 705 Total current assets 2,921 1,645 535 (591 ) 4,510 Property, plant and equipment, net 2,507 3,695 237 (4 ) 6,435 Other Assets Investment in subsidiaries 266 — 7,581 (7,847 ) — Equity investments in affiliates — 180 2 — 182 Note receivable, less current portion — 2 — — — 2 Goodwill 360 179 — — 539 Intangible assets, net 455 55 — (3 ) 507 Nuclear decommissioning trust fund 692 — — — 692 Derivative instruments 126 — 2 31 — 159 Deferred income taxes 377 (135 ) (236 ) — 6 Other non-current assets 50 124 120 — 294 Non-current assets held for sale — 43 — — 43 Non-current assets - discontinued operations — 10,203 — (22 ) 10,181 Total other assets 2,326 10,653 7,498 (7,872 ) 12,605 Total Assets $ 7,754 $ 15,993 $ 8,270 $ (8,467 ) $ 23,550 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 183 $ 21 $ — $ 204 Accounts payable 609 47 55 — 711 Accounts payable — affiliate 742 (332 ) 181 (534 ) 57 Derivative instruments 556 38 — (57 ) 537 Cash collateral received in support of energy risk management activities 37 — — — 37 Accrued expenses and other current liabilities 304 64 401 — 769 Accrued expenses and other current liabilities - affiliate — — 161 — 161 Current liabilities held-for-sale — 72 — — 72 Current liabilities - discontinued operations — 859 5 — 864 Total current liabilities 2,248 931 824 (591 ) 3,412 Other Liabilities Long-term debt and capital leases 244 2,197 6,739 — 9,180 Nuclear decommissioning reserve 269 — — — 269 Nuclear decommissioning trust liability 415 — — — 415 Deferred income taxes 112 64 (155 ) — 21 Derivative instruments 136 7 — — 143 Out-of-market contracts, net 66 129 — — 195 Other non-current liabilities 410 201 391 — 1,002 Non-current liabilities held-for-sale — 8 — — 8 Non-current liabilities - discontinued operations — 6,859 — — 6,859 Total non-current liabilities 1,652 9,465 6,975 — 18,092 Total Liabilities 3,900 10,396 7,799 (591 ) 21,504 Redeemable noncontrolling interest in subsidiaries — 78 — — 78 Stockholders’ Equity 3,854 5,519 471 (7,876 ) 1,968 Total Liabilities and Stockholders’ Equity $ 7,754 $ 15,993 $ 8,270 $ (8,467 ) $ 23,550 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the nine months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income/(loss) $ 737 $ (28 ) $ (564 ) $ (827 ) $ (682 ) Loss from discontinued operations — (134 ) (664 ) — (798 ) Income from continuing operations 737 106 100 (827 ) 116 Adjustments to reconcile net income to net cash provided/(used) by operating activities: Distributions and equity in earnings of unconsolidated affiliates — (65 ) 3 62 — Depreciation, amortization and accretion 299 167 24 — 490 Provision for bad debts 42 — 15 — 57 Amortization of nuclear fuel 37 — — — 37 Amortization of financing costs and debt discount/premiums — 2 13 — 15 Adjustment for debt extinguishment — 3 — — 3 Amortization of intangibles and out-of-market contracts 20 59 — — 79 Amortization of unearned equity compensation — — 27 — 27 Impairment losses 42 18 — — 60 Changes in deferred income taxes and liability for uncertain tax benefits — (7 ) 6 — (1 ) Changes in nuclear decommissioning trust liability 20 — — — 20 Changes in derivative instruments (11 ) 43 12 (8 ) 36 Changes in collateral deposits in support of energy risk management activities (126 ) 23 — — (103 ) Proceeds from sale of emission allowances 21 — — — 21 Gain on sale of assets (4 ) — — — (4 ) Changes in other working capital (1,035 ) (484 ) 451 773 (295 ) Cash provided/(used) by continuing operations 42 (135 ) 651 — 558 Cash provided by discontinued operations — 178 — — 178 Net Cash Provided by Operating Activities 42 43 651 — 736 Cash Flows from Investing Activities Intercompany dividends — — 129 (129 ) — Acquisition of businesses, net of cash acquired — (12 ) — — (12 ) Capital expenditures (135 ) (18 ) (19 ) — (172 ) Purchases of emission allowances (47 ) — — — (47 ) Proceeds from sale of emission allowances 105 (1 ) — — 104 Investments in nuclear decommissioning trust fund securities (402 ) — — — (402 ) Proceeds from the sale of nuclear decommissioning trust fund securities 382 — — — 382 Proceeds from sale of assets, net of cash disposed of 36 — 273 — 309 Change in investments in unconsolidated affiliates — 24 — — 24 Other 30 — — — 30 Cash (used)/provided by continuing operations (31 ) (7 ) 383 (129 ) 216 Cash used by discontinued operations — (638 ) — — (638 ) Net Cash (Used)/Provided by Investing Activities (31 ) (645 ) 383 (129 ) (422 ) Cash Flows from Financing Activities Payments (for)/from intercompany loans 9 417 (426 ) — — Intercompany dividends — (129 ) — 129 — Payment of dividends to common stockholders — — (28 ) — (28 ) Net receipts from settlement of acquired derivatives that include financing elements — — — — — Proceeds from issuance of long-term debt — 94 214 — 308 Payments for short and long-term debt — (124 ) (219 ) — (343 ) Increase in notes receivable from affiliate — (125 ) — — (125 ) Net distributions to noncontrolling interests from subsidiaries — (18 ) — — (18 ) Payments of debt issuance costs — (34 ) (5 ) — (39 ) Other — (8 ) — — (8 ) Cash provided/(used) by continuing operations 9 73 (464 ) 129 (253 ) Cash provided by discontinued operations — 39 — — 39 Net Cash Provided/(Used) by Financing Activities 9 112 (464 ) 129 (214 ) Effect of exchange rate changes on cash and cash equivalents — (10 ) — — (10 ) Change in cash from discontinued operations — (421 ) — — (421 ) Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash 20 (79 ) 570 — 511 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 3 534 323 — 860 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 23 $ 455 $ 893 $ — $ 1,371 (a) All significant intercompany transactions have been eliminated in consolidation.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified for comparative purposes. The reclassifications did not affect results from operations, net assets or cash flows.
Revenue Recognition	Contract Amortization Assets and liabilities recognized from power sales agreements assumed at Fresh Start and through acquisitions related to the sale of electric capacity and energy in future periods for which the fair value has been determined to be significantly less (more) than market are amortized to revenue over the term of each underlying contract based on actual generation and/or contracted volumes. Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606 using the modified retrospective method applied to contracts that were not completed as of the adoption date. The Company recognized the cumulative effect of initially applying the new standard as a credit to the opening balance of accumulated deficit, resulting in a decrease of approximately $16 million . The adjustment primarily related to costs incurred to obtain a contract with customers and customer incentives. Following the adoption of the new standard, the Company’s revenue recognition of its contracts with customers remains materially consistent with its historical practice. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company's policies with respect to its various revenue streams are detailed below. In general, the Company applies the invoicing practical expedient to recognize revenue for the revenue streams detailed below, except in circumstances where the invoiced amount does not represent the value transferred to the customer. Retail Revenues Gross revenues for energy sales and services to retail customers are recognized as the Company transfers the promised goods and services to the customer. For the majority of its electricity contracts, the Company’s performance obligation with the customer is satisfied over time and performance obligations for its electricity products are recognized as the customer takes possession of the product. The Company also allocates the contract consideration to distinct performance obligation in a contract for which the timing of the revenue recognized is different. Additionally, customer discounts and incentives reduce the contract consideration and are recognized over the term of the contract. Energy sales and services that have been delivered but not billed by period end are estimated. Accrued unbilled revenues are based on estimates of customer usage since the date of the last meter reading provided by the independent system operators or electric distribution companies. Volume estimates are based on daily forecasted volumes and estimated customer usage by class. Unbilled revenues are calculated by multiplying these volume estimates by the applicable rate by customer class. Estimated amounts are adjusted when actual usage is known and billed. As contracts for retail electricity can be for multi-year periods, the Company has performance obligations under these contracts that have not yet been satisfied. These performance obligations have transaction prices that are both fixed and variable, and that vary based on the contract duration, customer type, inception date and other contract-specific factors. For the fixed price contracts, the amount of any unsatisfied performance obligations will vary based on customer usage, which will depend on factors such as weather and customer activity and therefore it is not practicable to estimate such amounts. Energy Revenue Both physical and financial transactions are entered into to optimize the financial performance of the Company's generating facilities. Electric energy revenue is recognized upon transmission to the customer over time, using the output method for measuring progress of satisfaction of performance obligations. Physical transactions, or the sale of generated electricity to meet supply and demand, are recorded on a gross basis in the Company's consolidated statements of operations. The Company applies the invoicing practical expedient, where applicable, in recognizing energy revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Financial transactions, or the buying and selling of energy for trading purposes, are recorded net within operating revenues in the consolidated statements of operations in accordance with ASC 815. Capacity Revenue Capacity revenues consist of revenues billed to a third party at either the market or a negotiated contract price for making installed generation and demand response capacity available in order to satisfy system integrity and reliability requirements. Capacity revenues are recognized over time, using the output method for measuring progress of satisfaction of performance obligations. The Company applies the invoicing practical expedient, where applicable, in recognizing capacity revenue. Under the practical expedient, revenue is recognized based on the invoiced amount which is equal to the value to the customer of NRG’s performance obligation completed to date. Capacity revenue contracts mainly consist of: Capacity auctions — The Company's largest sources of capacity revenues are capacity auctions in PJM, ISO-NE, and NYISO. Both ISO-NE and PJM operate a pay-for-performance model where capacity payments are modified based on real-time performance, where NRG's actual revenues will be the combination of revenues based on the cleared auction MWs plus the net of any over- and under-performance of NRG's fleet. In addition, MISO has an annual auction, known as the Planning Resource Auction, or PRA. The Gulf Coast assets situated in the MISO market may participate in this auction. Estimated future revenues for cleared auction MWs in the various capacity auctions are $152 million , $610 million , $459 million , $528 million and $244 million for fiscal years 2018 , 2019 , 2020 , 2021 and 2022 , respectively. Resource adequacy and bilateral contracts — In California, there is a resource adequacy requirement that is primarily satisfied through bilateral contracts. Such bilateral contracts are typically short-term resource adequacy contracts. When bilateral contracting does not satisfy the resource adequacy need, such shortfalls can be addressed through procurement tools administered by the CAISO, including the capacity procurement mechanism or reliability must-run contracts. Demand payments from the current long-term contracts are tied to summer peak demand and provide a mechanism for recovering a portion of the costs associated with new or changed environmental laws or regulations. In Texas, capacity and contracted revenues are through bilateral contracts with load serving entities. Renewable Energy Credits As stated above, renewable energy credits are usually sold through long-term PPAs. Revenue from the sale of self-generated RECs is recognized when related energy is generated and simultaneously delivered even in cases where there is a certification lag as it has been deemed to be perfunctory. In a bundled contract to sell energy, capacity and/or self-generated RECs, all performance obligations are deemed to be delivered at the same time and hence, timing of recognition of revenue for all performance obligations is the same and occurs over time. In such cases, it is often unnecessary to allocate transaction price to multiple performance obligations. Sale of Emission Allowances The Company records its inventory of emission allowances as part of intangible assets. From time to time, management may authorize the transfer of emission allowances in excess of expected usage from the Company's emission bank to intangible assets held-for-sale for trading purposes. The Company records the sale of emission allowances on a net basis within operating revenue in the Company's consolidated statements of operations. When the Company receives consideration from the customer that is in excess of the amount due, such consideration is reclassified to deferred revenue, which represents a contract liability. Generally, the Company will recognize revenue from contract liabilities in the next period as the Company satisfies its performance obligations. The Company’s customer acquisition costs consist of broker fees, commission payments and other costs that represent incremental costs of obtaining the contract with customers for which the Company expects to recover. The Company amortizes these amounts over the estimated life of the customer contract. As a practical expedient, the Company expenses the incremental costs of obtaining a contract if the amortization period of the asset would have been one year or less.
Lease Revenue	Lease Revenue Certain of the Company’s revenues are obtained through leases of rooftop residential solar systems, which are accounted for as operating leases in accordance with ASC 840, Leases. Pursuant to the lease agreements, the customers’ monthly payments are pre-determined fixed monthly amounts and may include an annual fixed percentage escalation to reflect the impact of utility rate increases over the lease term, which is 20 years. The Company records operating lease revenue on a straight-line basis over the life of the lease term. Certain customers made initial down payments that are being amortized over the life of the lease. The difference between the payments received and the revenue recognized is recorded as deferred revenue.
Recent Accounting Developments	Recent Accounting Developments - Guidance Adopted in 2018 ASU 2017-07 — In March 2017, the FASB issued ASU No. 2017-07, Compensation - Retirement Benefits (Topic 715) , Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost, or ASU No. 2017-07. Current GAAP does not indicate where the amount of net benefit cost should be presented in an entity’s income statement and does not require entities to disclose the amount of net benefit cost that is included in the income statement. The amendments of ASU No. 2017-07 require an entity to report the service cost component of net benefit costs in the same line item as other compensation costs arising from services rendered by the related employees during the applicable service period. The other components of net benefit cost are required to be presented separately from the service cost component and outside the subtotal of income from operations. Further, ASU No. 2017-07 prescribes that only the service cost component of net benefit costs is eligible for capitalization. The Company adopted the amendments of ASU No. 2017-07 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance retrospectively which resulted in an increase in cost of operations of $4 million and $13 million with a corresponding increase in other income, net on the statement of operations for the three and nine months ended September 30, 2017 , respectively. ASU 2016-01 - In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , or ASU No. 2016-01. The amendments of ASU No. 2016-01 eliminate available-for-sale classification of equity investments and require that equity investments (except those accounted for under the equity method of accounting, or those that result in consolidation of the investee) be generally measured at fair value with changes in fair value recognized in net income. Further, the amendments require that financial assets and financial liabilities be presented separately in the notes to the financial statements, grouped by measurement category and form of financial asset. The guidance in ASU No. 2016-01 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those annual periods. The Company adopted the amendments of ASU No. 2016-01 effective January 1, 2018. In connection with the adoption of the standard, the Company has applied the guidance on a modified retrospective basis, which resulted in no material adjustments recorded to the consolidated results of operations, cash flows, and statement of financial position. Recent Accounting Developments - Guidance Not Yet Adopted ASU 2018-15 - In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other- Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , or ASU No. 2018-15. The amendments of ASU No. 2018-15 addresses customer’s accounting for implementation costs incurred in a cloud computing arrangement that is a service contract and also adds certain disclosure requirements related to implementation costs incurred for internal-use software and cloud computing arrangements. The amendment aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). ASU No. 2018-15 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted. The amendments in ASU No. 2018-15 can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is evaluating the impact of adopting this guidance on the consolidated financial statements and disclosures. ASU 2018-14 - In August 2018, the FASB issued ASU No. 2018-14, Compensation - Retirement benefits (Topic 715-20): Disclosure Framework - Changes to Disclosure Requirements for Defined Benefit Plans , or ASU No. 2018-14. The guidance in ASU No. 2018-14 adds, removes and clarifies disclosure requirements related to defined benefit pension and other postretirement plans. The amendments in ASU No. 2018-14 eliminate the requirement to disclose the amounts in accumulated other comprehensive income expected to be recognized as part of net periodic benefit cost over the next year. The guidance also removes the disclosure requirements for the effects of a one-percentage-point change on the assumed health care costs and the effect of this change in rates on service cost, interest cost and the benefit obligation for postretirement health care benefits. ASU No. 2018-14 is effective for fiscal years ending after December 15, 2020 and must be applied on a retrospective basis. As the amendment contemplates changes in disclosures only, it will have no material impact on the Company's results of operations, cash flows, or statement of financial position. ASU 2018-13 - In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirement for Fair value Measurement) , or ASU No. 2018-13. The guidance in ASU No. 2018-13 eliminates such disclosures as the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy. The amendments in ASU No. 2018-13 add new disclosure requirements for Level 3 measurements. ASU No. 2018-13 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years, with early adoption permitted for any eliminated or modified disclosures. Certain disclosures in ASU No. 2018-13 are required to be applied on a retrospective basis and others on a prospective basis. As the amendment contemplates changes in disclosures only, it will have no material impact on the Company's results of operations, cash flows, or statement of financial position. ASU 2016-02 — In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) , or Topic 842, with the objective to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and to improve financial reporting by expanding the related disclosures. The guidance in Topic 842 provides that a lessee that may have previously accounted for a lease as an operating lease under current GAAP should recognize the assets and liabilities that arise from a lease on the balance sheet. In addition, Topic 842 expands the required quantitative and qualitative disclosures with regards to lease arrangements. The Company will adopt the standard effective January 1, 2019, and expects to elect certain of the practical expedients permitted, including the expedient that permits the Company to retain its existing lease assessment and classification. The Company is currently working through an adoption plan which includes the evaluation of lease contracts compared to the new standard. While the Company is currently evaluating the impact the new guidance will have on its financial position and results of operations, the Company expects to recognize lease liabilities and right of use assets. The extent of the increase to assets and liabilities associated with these amounts remains to be determined pending the Company’s review of its existing lease contracts and service contracts which may contain embedded leases. While this review is still in process, NRG believes the adoption of Topic 842 will have a material impact on its financial statements. The Company is also monitoring recent changes to Topic 842 and the related impact on the implementation process.
Nuclear Decommissioning	NRG's Nuclear Decommissioning Trust Fund assets are comprised of securities classified as available-for-sale and recorded at fair value based on actively quoted market prices. NRG accounts for the Nuclear Decommissioning Trust Fund in accordance with ASC 980, Regulated Operations , because the Company's nuclear decommissioning activities are subject to approval by the PUCT with regulated rates that are designed to recover all decommissioning costs and that can be charged to and collected from the ratepayers per PUCT mandate. Since the Company is in compliance with PUCT rules and regulations regarding decommissioning trusts and the cost of decommissioning is the responsibility of the Texas ratepayers, not NRG, all realized and unrealized gains or losses (including other-than-temporary impairments) related to the Nuclear Decommissioning Trust Fund are recorded to the Nuclear Decommissioning Trust liability and are not included in net income or accumulated OCI, consistent with regulatory treatment.
Segment Reporting	The Company's segment structure reflects how management currently makes financial decisions and allocates resources. The Company's businesses are segregated as follows: Generation, which includes generation, Renewables and international; Retail, which includes Mass customers and Business Solutions, which includes C&I customers and other distributed and reliability products; and corporate activities. The financial information for the three and nine months ended September 30, 2018 has been recast to reflect the current segment structure. On August 31, 2018, as described in Note 3 , Acquisitions, Discontinued Operations and Dispositions , NRG deconsolidated NRG Yield, Inc., its Renewables Platform and Carlsbad for financial reporting purposes. The financial information for all historical periods has been recast to reflect the presentation of these entities as discontinued operations within the corporate segment. On June 14, 2017, as described in Note 3 , Acquisitions, Discontinued Operations and Dispositions , NRG deconsolidated GenOn for financial reporting purposes. The financial information for all historical periods has been recast to reflect the presentation of GenOn as discontinued operations within the corporate segment. NRG’s chief operating decision maker, its chief executive officer, evaluates the performance of its segments based on operational measures including adjusted earnings before interest, taxes, depreciation and amortization, or Adjusted EBITDA, free cash flow and capital for allocation, as well as net income/(loss).

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Other Balance Sheet Information	The following table presents the allowance for doubtful accounts included in accounts receivable, net; accumulated depreciation included in property, plant and equipment, net; accumulated amortization included in intangible assets, net and accumulated amortization included in out-of-market contracts, net: September 30, 2018 December 31, 2017 (In millions) Accounts receivable allowance for doubtful accounts $ 37 $ 28 Property, plant and equipment accumulated depreciation 2,652 3,013 Intangible assets accumulated amortization 1,194 1,572 Out-of-market contracts accumulated amortization 372 354
Reconciliation of Cash and Cash Equivalents, Restricted Cash and Funds Deposited by Counterparties	The following table provides a reconciliation of cash and cash equivalents, restricted cash and funds deposited by counterparties reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the statement of cash flows. September 30, 2018 December 31, 2017 September 30, 2017 December 31, 2016 (In millions) Cash and cash equivalents $ 1,359 $ 767 $ 1,022 $ 591 Funds deposited by counterparties 30 37 31 2 Restricted cash 28 279 318 267 Cash and cash equivalents, funds deposited by counterparties and restricted cash shown in the statement of cash flows $ 1,417 $ 1,083 $ 1,371 $ 860
Schedule of Changes in Noncontrolling Interest	Noncontrolling Interest The following table reflects the changes in NRG's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 2,314 Dividends paid to NRG Yield, Inc. public shareholders (61 ) Distributions to noncontrolling interest (43 ) Net income attributable to noncontrolling interest - continuing operations 5 Net income attributable to noncontrolling interest - discontinued operations 21 Other comprehensive income attributable to noncontrolling interest - discontinued operations 14 Non-cash adjustments to noncontrolling interest 10 Contributions from noncontrolling interest 296 Sale of assets to NRG Yield, Inc. (8 ) Deconsolidation of Ivanpah (a) (89 ) Deconsolidation of Agua Caliente (b) (279 ) Deconsolidation of NRG Yield and the Renewables Platform (b) (2,180 ) Balance as of September 30, 2018 $ — (a) See Note 9 , Variable Interest Entities, or VIEs for further information regarding the deconsolidation of Ivanpah effective April 2018. (b) See Note 3 , Acquisitions, Discontinued Operations and Dispositions for further information regarding the sale of NRG Yield and the Renewables Platform and the deconsolidation of Agua Caliente.
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest The following table reflects the changes in the Company's redeemable noncontrolling interest balance: (In millions) Balance as of December 31, 2017 $ 78 Distributions to redeemable noncontrolling interest (3 ) Contributions from redeemable noncontrolling interest 26 Non-cash adjustments to redeemable noncontrolling interest (9 ) Net income attributable to redeemable noncontrolling interest - continuing operations 1 Net income attributable to redeemable noncontrolling interest - discontinued operations (26 ) Deconsolidation of NRG Yield and the Renewables Platform (a) (48 ) Balance as of September 30, 2018 $ 19 (a) See Note 3 , Acquisitions, Discontinued Operations and Dispositions for further information regarding the sale of NRG Yield and the Renewables Platform.
Disaggregation of Revenue from Contracts	The following table represents the Company’s disaggregation of revenue from contracts with customers for the three and nine months ended September 30, 2018 , along with the reportable segment for each category: Three months ended September 30, 2018 Generation (In millions) Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue (a) $ — $ 680 $ 278 $ 958 $ (479 ) $ 479 Capacity revenue (a) — 66 187 253 1 254 Retail revenue Mass customers 1,768 — — — (2 ) 1,766 Business Solutions customers 434 — — — — 434 Total retail revenue 2,202 — — — (2 ) 2,200 Mark-to-market for economic hedging activities (b) 1 268 27 295 (241 ) 55 Contract amortization — 5 — 5 — 5 Other revenue (a)(c) — 36 32 68 — 68 Total operating revenue 2,203 1,055 524 1,579 (721 ) 3,061 Less: Lease revenue 3 — 3 3 — 6 Less: Derivative revenue 1 1,160 55 1,215 (241 ) 975 Less: Contract amortization — 5 — 5 — 5 Total revenue from contracts with customers $ 2,199 $ (110 ) $ 466 $ 356 $ (480 ) $ 2,075 (a) The following amounts of energy and capacity revenue relate to derivative instruments and are accounted for under ASC 815. Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue $ — $ 896 $ (25 ) $ 871 $ — $ 871 Capacity revenue — — 45 45 — 45 Other revenue — (4 ) 8 4 — 4 (b) Revenue relates entirely to unrealized gains and losses on derivative instruments accounted for under ASC 815. (c) Included in other revenue is lease revenue of $3 million for both Retail and East/West/Other, respectively. Nine months ended September 30, 2018 Generation (In millions) Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue (a) $ — $ 1,558 $ 735 $ 2,293 $ (890 ) $ 1,403 Capacity revenue (a) — 201 — 487 — 688 — 688 Retail revenue Mass customers 4,321 — — — (4 ) 4,317 Business Solutions customers 1,181 — — — — 1,181 Total retail revenue 5,502 — — — (4 ) 5,498 Mark-to-market for economic hedging activities (b) (5 ) (7 ) 2 (5 ) (21 ) (31 ) Contract amortization — 12 — 12 — 12 Other revenue (c) — 164 64 228 (3 ) 225 Total operating revenue 5,497 1,928 1,288 3,216 (918 ) 7,795 Less: Lease revenue 10 — 6 6 — 16 Less: Derivative revenue (5 ) 1,871 135 2,006 — 2,001 Less: Contract amortization — 12 — 12 — 12 Total revenue from contracts with customers $ 5,492 $ 45 $ 1,147 $ 1,192 $ (918 ) $ 5,766 (a) The following amounts of energy and capacity revenue relate to derivative instruments and are accounted for under ASC 815. Retail Gulf Coast East/West/Other Subtotal Corporate/Eliminations Total Energy revenue $ — $ 1,877 $ 7 $ 1,884 $ — $ 1,884 Capacity revenue — — 110 110 — 110 Other revenue — 1 16 17 — 17 (b) Revenue relates entirely to unrealized gains and losses on derivative instruments accounted for under ASC 815. (c) Included in other revenue is lease revenue of $10 million and $6 million for Retail and East/West/Other, respectively.
Contract Asset and Liabilities	The following table reflects the contract assets and liabilities included in the Company’s balance sheet as of September 30, 2018 : (In millions) September 30, 2018 Deferred customer acquisition costs $ 104 Accounts receivable, net - Contracts with customers 1,265 Accounts receivable, net - Derivative instruments 32 Total accounts receivable, net $ 1,297 Unbilled revenues (included within Accounts receivable, net - Contracts with customers) 385 Deferred revenues 60

Acquisitions, Discontinued Op_2

Acquisitions, Discontinued Operations and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Summary of Results of Discontinued Operations and Major Classes of Assets and Liabilities	Summarized results of discontinued operations were as follows: Three months ended September 30, 2018 Three months ended September 30, 2017 Nine months ended September 30, 2018 Nine months ended September 30, 2017 (In millions) Operating revenues $ — $ — $ — $ 646 Operating costs and expenses — — — (700 ) Other expenses — — — (98 ) Loss from operations of discontinued components, before tax — — — (152 ) Income tax expense — — — 9 Loss from discontinued operations — — — (161 ) Interest income - affiliate — — 3 6 Loss from discontinued operations, net of tax — — 3 (155 ) Pre-tax loss on deconsolidation — — — (208 ) Settlement consideration and services credit — — 1 (289 ) Pension and post-retirement liability assumption — (25 ) (2 ) (144 ) Other — (2 ) (27 ) (6 ) Loss on disposal of discontinued operations, net of tax — (27 ) (28 ) (647 ) Loss from discontinued operations, net of tax $ — $ (27 ) $ (25 ) $ (802 ) Summarized results of discontinued operations were as follows: Three months ended September 30, 2018 Three months ended September 30, 2017 Nine months ended September 30, 2018 Nine months ended September 30, 2017 (In millions) Operating revenues $ 280 $ 315 $ 925 $ 906 Operating costs and expenses (212 ) (242 ) (682 ) (690 ) Other expenses (44 ) (64 ) (165 ) (210 ) Gain/(loss) from operations of discontinued components, before tax 24 9 78 6 Income tax expense 9 4 4 2 Gain/(loss) from discontinued operations, net of tax 15 5 74 4 Loss on deconsolidation, net of tax (139 ) — (139 ) — California property tax indemnification (153 ) — (153 ) — Other Commitments, Indemnification and Fees (77 ) — (77 ) — Loss on disposal of discontinued operations, net of tax (369 ) — (369 ) — Gain/(Loss) from discontinued operations, net of tax $ (354 ) $ 5 $ (295 ) $ 4 The following table summarizes the major classes of assets and liabilities classified as discontinued operations as follows: (In millions) September 30, 2018 (a) December 31, 2017 (b) Cash and cash equivalents $ — $ 224 Restricted Cash — 229 Accounts receivable, net — 119 Other current assets 4 133 Current assets - discontinued operations 4 705 Property, plant and equipment, net 547 7,473 Equity investments in affiliates — 856 Intangible assets, net 8 1,240 Other non-current assets 5 612 Non-current assets - discontinued operations 560 10,181 Current portion of long term debt and capital leases 14 484 Accounts payable 37 169 Other current liabilities 1 211 Current liabilities - discontinued operations 52 864 Long-term debt and capital leases 545 6,673 Other non-current liabilities 2 186 Non-current liabilities - discontinued operations $ 547 $ 6,859 (a) Represents the Carlsbad project. (b) Represents the discontinued operations of NRG Yield, NRG's Renewable Platform and the Carlsbad project.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Estimated carrying amounts and fair values of NRG's recorded financial instruments not carried at fair market value	The estimated carrying amounts and fair values of NRG's recorded financial instruments not carried at fair market value are as follows: As of September 30, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable (a) $ 11 $ 8 $ 2 $ 2 Liabilities: Long-term debt, including current portion (b) 7,331 7,653 9,482 9,739 (a) Includes the current portion of notes receivable which is recorded in prepayments and other current assets on the Company's consolidated balance sheets. (b) Excludes deferred financing costs, which are recorded as a reduction to long-term debt on the Company's consolidated balance sheets. The following table presents the level within the fair value hierarchy for long-term debt, including current portion as of September 30, 2018 and December 31, 2017 : As of September 30, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 7,385 $ 268 $ 7,432 $ 2,307
Assets and liabilities measured and recorded at fair value on the consolidated balance sheets on a recurring basis	The following tables present assets and liabilities measured and recorded at fair value on the Company's condensed consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of September 30, 2018 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 21 $ 2 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 21 21 — — U.S. government and federal agency obligations 41 41 — — Federal agency mortgage-backed securities 88 — 88 — Commercial mortgage-backed securities 19 — 19 — Corporate debt securities 112 — 112 — Equity securities 368 368 — — Foreign government fixed income securities 4 — 4 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 1,022 210 743 69 Interest rate contracts 53 — 53 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 66 Total assets $ 1,816 $ 643 $ 1,019 $ 88 Derivative liabilities: Commodity contracts 905 271 552 82 Interest rate contracts 2 — 2 — Total liabilities $ 907 $ 271 $ 554 $ 82 As of December 31, 2017 Fair Value (In millions) Total Level 1 Level 2 Level 3 Investments in securities (classified within other non-current assets) $ 22 $ 3 $ — $ 19 Nuclear trust fund investments: Cash and cash equivalents 47 45 2 — U.S. government and federal agency obligations 43 42 1 — Federal agency mortgage-backed securities 82 — 82 — Commercial mortgage-backed securities 14 — 14 — Corporate debt securities 99 — 99 — Equity securities 334 334 — — Foreign government fixed income securities 5 — 5 — Other trust fund investments: U.S. government and federal agency obligations 1 1 — — Derivative assets: Commodity contracts 744 191 509 44 Interest rate contracts 39 — 39 — Measured using net asset value practical expedient: Equity securities — nuclear trust fund investments 68 Total assets $ 1,498 $ 616 $ 751 $ 63 Derivative liabilities: Commodity contracts 674 257 358 59 Interest rate contracts 6 — 6 — Total liabilities $ 680 $ 257 $ 364 $ 59
Reconciliation of beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements at least annually using significant unobservable inputs	The following tables reconcile, for the three and nine months ended September 30, 2018 and 2017 , the beginning and ending balances for financial instruments that are recognized at fair value in the condensed consolidated financial statements, at least annually, using significant unobservable inputs: Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended September 30, 2018 Nine months ended September 30, 2018 (In millions) Debt Securities Derivatives (a) Total Debt Securities Derivatives (a) Total Beginning balance $ 19 $ 174 $ 193 $ 19 $ (15 ) $ 4 Contracts acquired in Xoom acquisition — — — — 12 12 Total losses — realized/unrealized — — — — (15 ) (15 ) Purchases — 12 12 — 9 9 Transfers into Level 3 (b) — (201 ) (201 ) — (4 ) (4 ) Transfers out of Level 3 (b) — 2 2 — — — Ending balance as of September 30, 2018 $ 19 $ (13 ) $ 6 $ 19 $ (13 ) $ 6 Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of September 30, 2018 — (3 ) (3 ) — (18 ) (18 ) (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2. Fair Value Measurement Using Significant Unobservable Inputs (Level 3) Three months ended September 30, 2017 Nine months ended September 30, 2017 (In millions) Debt Securities Derivatives (a) Total Debt Securities Derivatives (a) Total Beginning balance $ 18 $ (9 ) $ 9 $ 17 $ (64 ) $ (47 ) Total gains/(losses) — realized/unrealized included in earnings 1 (32 ) (31 ) 2 12 14 Purchases — (9 ) (9 ) — — — Transfers into Level 3 (b) — (7 ) (7 ) — (11 ) (11 ) Transfers out of Level 3 (b) — 7 7 — 13 13 Ending balance as of September 30, 2017 $ 19 $ (50 ) $ (31 ) $ 19 $ (50 ) $ (31 ) Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held as of September 30, 2017 — (16 ) (16 ) — (12 ) (12 ) (a) Consists of derivative assets and liabilities, net. (b) Transfers into/out of Level 3 are related to the availability of external broker quotes and are valued as of the end of the reporting period. All transfers in/out are with Level 2.
Significant unobservable inputs used developing fair values, Quantitative Information	The following tables quantify the significant unobservable inputs used in developing the fair value of the Company's Level 3 positions as of September 30, 2018 and December 31, 2017 : Significant Unobservable Inputs September 30, 2018 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 44 $ 68 Discounted Cash Flow Forward Market Price (per MWh) $ 2 $ 197 $ 23 FTRs 25 14 Discounted Cash Flow Auction Prices (per MWh) (90 ) 86 — $ 69 $ 82 Significant Unobservable Inputs December 31, 2017 Fair Value Input/Range Assets Liabilities Valuation Technique Significant Unobservable Input Low High Weighted Average (In millions) Power Contracts $ 33 $ 47 Discounted Cash Flow Forward Market Price (per MWh) $ 10 $ 142 $ 24 FTRs 11 12 Discounted Cash Flow Auction Prices (per MWh) (28 ) 46 — $ 44 $ 59
Fair value inputs, sensitivity analysis	The following table provides sensitivity of fair value measurements to increases/(decreases) in significant unobservable inputs as of September 30, 2018 and December 31, 2017 : Significant Unobservable Input Position Change In Input Impact on Fair Value Measurement Forward Market Price Power Buy Increase/(Decrease) Higher/(Lower) Forward Market Price Power Sell Increase/(Decrease) Lower/(Higher) FTR Prices Buy Increase/(Decrease) Higher/(Lower) FTR Prices Sell Increase/(Decrease) Lower/(Higher)
Net counterparty credit exposure by industry sector and by counterparty credit quality	The following tables highlight net counterparty credit exposure by industry sector and by counterparty credit quality. Net counterparty credit exposure is defined as the aggregate net asset position for NRG with counterparties where netting is permitted under the enabling agreement and includes all cash flow, mark-to-market and NPNS, and non-derivative transactions. The exposure is shown net of collateral held, and includes amounts net of receivables or payables. Net Exposure (a) (b) Category by Industry Sector (% of Total) Utilities, energy merchants, marketers and other 83 % Financial institutions 17 Total as of September 30, 2018 100 % Net Exposure (a) (b) Category by Counterparty Credit Quality (% of Total) Investment grade 59 % Non-Investment grade/Non-Rated 41 Total as of September 30, 2018 100 % (a) Counterparty credit exposure excludes uranium and coal transportation contracts because of the unavailability of market prices. (b) The figures in the tables above exclude potential counterparty credit exposure related to RTOs, ISOs, registered commodity exchanges and certain long term contracts.

Nuclear Decommissioning Trust_2

Nuclear Decommissioning Trust Fund (Tables)	9 Months Ended
	Sep. 30, 2018
Nuclear Decommissioning Trust Fund Disclosure [Abstract]
Summary of aggregate fair values and unrealized gains and losses (including other-than-temporary impairments) for the securities held in the nuclear decommissioning trust fund	The following table summarizes the aggregate fair values and unrealized gains and losses (including other-than-temporary impairments) for the securities held in the trust funds, as well as information about the contractual maturities of those securities. As of September 30, 2018 As of December 31, 2017 (In millions, except otherwise noted) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Fair Value Unrealized Gains Unrealized Losses Weighted-average Maturities (In years) Cash and cash equivalents $ 21 $ — $ — — $ 47 $ — $ — — U.S. government and federal agency obligations 41 1 1 12 43 1 — 11 Federal agency mortgage-backed securities 88 — 3 23 82 1 1 23 Commercial mortgage-backed securities 19 — 1 22 14 — — 20 Corporate debt securities 112 1 2 10 99 2 1 11 Equity securities 434 296 — — 402 272 — — Foreign government fixed income securities 4 — — 9 5 — — 9 Total $ 719 $ 298 $ 7 $ 692 $ 276 $ 2
Summary of proceeds from sales of available-for-sale securities and the related realized gains and losses	The following table summarizes proceeds from sales of available-for-sale securities and the related realized gains and losses from these sales. The cost of securities sold is determined on the specific identification method. Nine months ended September 30, 2018 2017 (In millions) Realized gains $ 8 $ 8 Realized losses 8 6 Proceeds from sale of securities $ 398 $ 382

Accounting for Derivative Ins_2

Accounting for Derivative Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net notional volume buy/(sell) of NRG's open derivative transactions broken out by commodity	The following table summarizes the net notional volume buy/(sell) of NRG's open derivative transactions broken out by category, excluding those derivatives that qualified for the NPNS exception, as of September 30, 2018 and December 31, 2017 . Option contracts are reflected using delta volume. Delta volume equals the notional volume of an option adjusted for the probability that the option will be in-the-money at its expiration date. Total Volume September 30, 2018 December 31, 2017 Category Units (In millions) Emissions Short Ton 3 1 Renewable Energy Certificates Certificates 1 — Coal Short Ton 8 21 Natural Gas MMBtu (439 ) (20 ) Power MWh 8 23 Capacity MW/Day (1 ) (1 ) Interest Dollars $ 1,058 $ 1,060 Equity Shares — 1
Fair value within the derivative instrument valuation on the balance sheets	The following table summarizes the fair value within the derivative instrument valuation on the balance sheets: Fair Value Derivative Assets Derivative Liabilities September 30, 2018 December 31, 2017 September 30, 2018 December 31, 2017 (In millions) Derivatives Not Designated as Cash Flow or Fair Value Hedges: Interest rate contracts current 17 8 — 1 Interest rate contracts long-term 36 31 2 5 Commodity contracts current 666 616 550 536 Commodity contracts long-term 356 128 355 138 Total Derivatives Not Designated as Cash Flow or Fair Value Hedges 1,075 783 907 680
Offsetting of derivatives by counterparty assets	The following table summarizes the offsetting of derivatives by counterparty master agreement level and collateral received or paid: Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of September 30, 2018 (In millions) Commodity contracts: Derivative assets $ 1,022 $ (765 ) $ (18 ) $ 239 Derivative liabilities (905 ) 765 30 (110 ) Total commodity contracts 117 — 12 129 Interest rate contracts: Derivative assets 53 — — 53 Derivative liabilities (2 ) — — (2 ) Total interest rate contracts 51 — — 51 Total derivative instruments $ 168 $ — $ 12 $ 180 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of December 31, 2017 (In millions) Commodity contracts: Derivative assets $ 744 $ (578 ) $ (11 ) $ 155 Derivative liabilities (674 ) 578 72 (24 ) Total commodity contracts 70 — 61 131 Interest rate contracts: Derivative assets 39 — — 39 Derivative liabilities (6 ) — — (6 ) Total interest rate contracts 33 — — 33 Total derivative instruments $ 103 $ — $ 61 $ 164
Offsetting of derivatives by counterparty, liabilities	The following table summarizes the offsetting of derivatives by counterparty master agreement level and collateral received or paid: Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of September 30, 2018 (In millions) Commodity contracts: Derivative assets $ 1,022 $ (765 ) $ (18 ) $ 239 Derivative liabilities (905 ) 765 30 (110 ) Total commodity contracts 117 — 12 129 Interest rate contracts: Derivative assets 53 — — 53 Derivative liabilities (2 ) — — (2 ) Total interest rate contracts 51 — — 51 Total derivative instruments $ 168 $ — $ 12 $ 180 Gross Amounts Not Offset in the Statement of Financial Position Gross Amounts of Recognized Assets / Liabilities Derivative Instruments Cash Collateral (Held) / Posted Net Amount As of December 31, 2017 (In millions) Commodity contracts: Derivative assets $ 744 $ (578 ) $ (11 ) $ 155 Derivative liabilities (674 ) 578 72 (24 ) Total commodity contracts 70 — 61 131 Interest rate contracts: Derivative assets 39 — — 39 Derivative liabilities (6 ) — — (6 ) Total interest rate contracts 33 — — 33 Total derivative instruments $ 103 $ — $ 61 $ 164
Effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax	The following table summarizes the effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax: Interest Rate Contracts Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 (In millions) Accumulated OCI beginning balance $ (23 ) $ (67 ) $ (54 ) $ (66 ) Reclassified from accumulated OCI to income: Due to realization of previously deferred amounts 1 4 8 10 Mark-to-market of cash flow hedge accounting contracts (3 ) 4 21 (3 ) Sale of NRG Yield and the Renewables Platform 25 — 25 — Accumulated OCI ending balance, net of $0, and $15 tax $ — $ (59 ) $ — $ (59 )
Pre-tax effects of economic hedges that have not been designated as cash flow hedges, ineffectiveness on cash flow hedges and trading activity on the Company's statement of operations	The following table summarizes the pre-tax effects of economic hedges that have not been designated as cash flow hedges and trading activity on the Company's statement of operations. The effect of energy commodity contracts is included within operating revenues and cost of operations and the effect of interest rate contracts is included in interest expense. Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 Unrealized mark-to-market results (In millions) Reversal of previously recognized unrealized (gains)/losses on settled positions related to economic hedges $ (84 ) $ (7 ) $ (85 ) $ 18 Reversal of acquired gain positions related to economic hedges (10 ) (2 ) (11 ) (1 ) Net unrealized gains/(losses) on open positions related to economic hedges 25 (19 ) 158 (8 ) Total unrealized mark-to-market (losses)/gains for economic hedging activities (69 ) (28 ) 62 9 Reversal of previously recognized unrealized gains on settled positions related to trading activity (4 ) (5 ) (10 ) (24 ) Net unrealized gains on open positions related to trading activity 8 — 27 17 Total unrealized mark-to-market gains/(losses) for trading activity 4 (5 ) 17 (7 ) Total unrealized (losses)/gains $ (65 ) $ (33 ) $ 79 $ 2 Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 (In millions) Unrealized gains/(losses) included in operating revenues $ 59 $ 17 $ (14 ) $ 170 Unrealized (losses)/gains included in cost of operations (124 ) (50 ) 93 (168 ) Total impact to statement of operations — energy commodities $ (65 ) $ (33 ) $ 79 $ 2 Total impact to statement of operations — interest rate contracts $ 2 $ 3 $ 17 $ (4 )

Debt and Capital Leases (Tables

Debt and Capital Leases (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Long-term debt and capital leases	Long-term debt and capital leases consisted of the following: (In millions, except rates) September 30, 2018 December 31, 2017 September 30, 2018 interest rate % (a) Recourse debt: Senior Notes, due 2022 $ 485 $ 992 6.250 Senior Notes, due 2024 733 733 6.250 Senior Notes, due 2026 1,000 1,000 7.250 Senior Notes, due 2027 1,230 1,250 6.625 Senior Notes, due 2028 821 870 5.750 Convertible Senior Notes, due 2048 575 — 2.750 Term loan facility, due 2023 1,857 1,872 L+1.75 Tax-exempt bonds 466 465 4.125 - 6.00 Subtotal recourse debt 7,167 7,182 Non-recourse debt: Ivanpah, due 2033 and 2038 (b) — 1,073 2.285 - 4.256 Agua Caliente, due 2037 (c) — 818 2.395 - 3.633 Agua Caliente Borrower 1, due 2038 86 89 5.430 Midwest Generation, due 2019 78 152 4.390 Other 105 180 various Subtotal all non-recourse debt 269 2,312 Subtotal long-term debt (including current maturities) 7,436 9,494 Capital leases 2 5 various Subtotal long-term debt and capital leases (including current maturities) 7,438 9,499 Less current maturities (593 ) (204 ) Less debt issuance costs (82 ) (103 ) Discounts (105 ) (12 ) Total long-term debt and capital leases $ 6,658 $ 9,180 (a) As of September 30, 2018 , L+ equals 3-month LIBOR plus 1.75% . (b) The Company deconsolidated Ivanpah during the second quarter of 2018. (c) The Company deconsolidated Agua Caliente solar facility during the third quarter of 2018.
Senior notes repurchased	Principal Repurchased Cash Paid (a) Average Early Redemption Percentage In millions, except rates 5.750% senior notes due 2028 $ 29 $ 30 99.24 % 6.250% senior notes due 2022 14 15 103.25 % Total at June 30, 2018 $ 43 $ 45 6.250% senior notes due 2022 (b) 492 512 103.13 % 5.750% senior notes due 2028 20 20 99.13 % 6.625% senior notes due 2027 20 21 103.06 % Total at September 30, 2018 $ 575 $ 598 (a) Includes payment for accrued interest of $7 million as of September 30, 2018 (b) Includes partial redemption of $486 million during the third quarter of 2018

Variable Interest Entities, o_2

Variable Interest Entities, or VIEs (Tables)	9 Months Ended
	Sep. 30, 2018
Variable Interest Entities Disclosure [Abstract]
Financial Information for Consolidated VIEs	The summarized financial information for the Company's consolidated VIEs consisted of the following: (In millions) September 30, 2018 December 31, 2017 Current assets $ 6 $ 6 Net property, plant and equipment 76 80 Other long-term assets 31 36 Total assets 113 122 Current liabilities 2 3 Long-term debt 29 30 Other long-term liabilities 8 7 Total liabilities 39 40 Redeemable noncontrolling interest 19 19 Net assets less noncontrolling interests $ 55 $ 63

Changes in Capital Structure (T

Changes in Capital Structure (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Changes in NRG's common shares issued and outstanding	The following table reflects the changes in NRG's common stock issued and outstanding: Issued Treasury Outstanding Balance as of December 31, 2017 418,323,134 (101,580,045 ) 316,743,089 Shares issued under LTIPs 1,555,766 — 1,555,766 Shares issued under ESPP — 175,862 175,862 Shares repurchased — (28,544,693 ) (28,544,693 ) Balance as of September 30, 2018 419,878,900 (129,948,876 ) 289,930,024
Shares Repurchased	The following repurchases have been made during the nine months ended September 30, 2018. Total number of shares purchased Average price paid per share Amounts paid for shares purchased (in millions) Board Authorized Share Repurchases First Quarter 2018 (a) 3,114,748 $ 93 Second Quarter 2018 (a) (b) 11,748,553 407 Third Quarter 2018 (b) 13,681,392 500 Total Board Authorized Share Repurchases as of September 30, 2018 28,544,693 (c) $ 1,000 (a) The average price paid per share and amounts paid for shares purchased exclude the commissions of $0.01 per share paid in connection with the open market share repurchase. (b) The share repurchases for the second and the third quarter include 9,969,023 and 13,681,392 respectively of the shares repurchased through the ASR Agreements, as described below. (c) The total number of shares repurchased under the $1 billion share repurchase program and the average price paid per share will be determined upon final settlement of the September ASR in which the financial institution may deliver additional shares to the Company.
Schedule of dividends paid	The following table lists the dividends paid during the nine months ended September 30, 2018 : Third Quarter 2018 Second Quarter 2018 First Quarter 2018 Dividends per Common Share $ 0.03 $ 0.03 $ 0.03

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of segment reporting information, by segment	Retail (a) Generation (a) Corporate (a) Eliminations Total Three months ended September 30, 2018 (In millions) Operating revenues (a) $ 2,203 $ 1,579 $ 1 $ (722 ) $ 3,061 Depreciation and amortization 30 73 7 2 112 Reorganization costs 6 3 18 — 27 Gain on sale of assets — — 14 — 14 Equity in earnings of unconsolidated affiliates — 20 2 (2 ) 20 Loss on debt extinguishment, net — — (19 ) — (19 ) (Loss)/income from continuing operations before income taxes (127 ) 595 349 (504 ) 313 (Loss)/income from continuing operations (127 ) 595 342 (504 ) 306 Loss from discontinued operations, net of tax — — (354 ) — (354 ) Net (Loss)/Income (127 ) 595 (12 ) (504 ) (48 ) (Loss)/Income attributable to NRG Energy, Inc. common stockholders $ (127 ) $ 579 $ (23 ) $ (501 ) — $ (72 ) Total assets as of September 30, 2018 $ 3,465 $ 6,699 $ 7,979 $ (6,693 ) $ 11,450 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 1 $ 740 $ (19 ) $ — $ 722 Retail (a) Generation (a) Corporate (a) Eliminations Total Three months ended September 30, 2017 (In millions) Operating revenues (a) $ 1,936 $ 1,313 $ — $ (509 ) $ 2,740 Depreciation and amortization 28 128 8 (1 ) 163 Reorganization costs 5 3 4 — 12 Equity in earnings of unconsolidated affiliates — 9 3 (3 ) 9 Income/(loss) from continuing operations before income taxes 72 272 (157 ) (1 ) 186 Income/(loss) from continuing operations 72 272 (158 ) (1 ) 185 Loss from discontinued operations, net of tax — — (22 ) — (22 ) Net Income/(Loss) 72 272 (180 ) (1 ) 163 Net Income/(Loss) attributable to NRG Energy, Inc. common stockholders $ 72 $ 256 $ (159 ) $ 2 $ 171 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 3 $ 493 $ 13 $ — $ 509 Retail (a) Generation (a) Corporate (a) Eliminations Total Nine months ended September 30, 2018 (In millions) Operating revenues (a) $ 5,497 $ 3,216 $ 10 $ (928 ) $ 7,795 Depreciation and amortization 86 259 25 — 370 Impairment losses — 74 — — 74 Reorganization costs 10 10 50 — — 70 Gain on sale of assets — 1 29 — 30 Equity in earnings of unconsolidated affiliates — 27 4 (5 ) 26 Loss on debt extinguishment, net — — (22 ) — (22 ) Income/(Loss) from continuing operations before income taxes 733 303 812 (1,228 ) 620 Income/(Loss) from continuing operations 733 302 794 (1,228 ) 601 Loss from discontinued operations, net of tax — — (320 ) — (320 ) Net Income/(Loss) 733 302 474 (1,228 ) 281 Net Income/(Loss) attributable to NRG Energy, Inc. common stockholders $ 732 $ 293 $ 479 $ (1,224 ) $ 280 (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 7 $ 944 $ (23 ) $ — $ 928 Retail (a) Generation (a) Corporate (a) Eliminations Total Nine months ended September 30, 2017 Operating revenues (a) $ 4,868 $ 3,289 $ 13 $ (924 ) $ 7,246 Depreciation and amortization 81 385 26 (2 ) 490 Impairment losses — 60 — — 60 Reorganization costs 5 3 10 — — 18 Gain on sale of assets — 4 — — 4 Equity in (losses)/earnings of unconsolidated affiliates — (21 ) 6 (5 ) (20 ) Income/(loss) from continuing operations before income taxes 371 185 (433 ) (4 ) 119 Income/(loss) from continuing operations 380 183 (443 ) (4 ) 116 Loss from discontinued operations, net of tax — — (798 ) — (798 ) Net Income/(loss) 380 183 (1,241 ) (4 ) (682 ) Net Income/(loss) attributable to NRG Energy, Inc. common stockholders $ 380 $ 169 $ (1,169 ) $ 1 $ (619 ) (a) Operating revenues include inter-segment sales and net derivative gains and losses of: $ 3 $ 872 $ 49 $ — $ 924

Earnings_(Loss) Per Share (Tabl

Earnings/(Loss) Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Reconciliation of NRG's basic and diluted earnings per share	The reconciliation of NRG's basic and diluted loss per share is shown in the following table: Three months ended September 30, Nine months ended September 30, In millions, except per share data 2018 2017 2018 2017 Basic income/(loss) per share attributable to NRG Energy, Inc. common stockholders Net (loss)/income attributable to NRG Energy, Inc. common stockholders $ (72 ) $ 171 $ 280 $ (619 ) Weighted average number of common shares outstanding - basic 299 317 309 317 (Loss)/earnings per weighted average common share — basic $ (0.24 ) $ 0.54 $ 0.91 $ (1.95 ) Diluted income/(loss) per share attributable to NRG Energy, Inc. common stockholders Weighted average number of common shares outstanding - diluted 299 317 309 317 Incremental shares attributable to the issuance of equity compensation (treasury stock method) — 5 4 — Total dilutive shares 299 322 313 317 (Loss)/income per weighted average common share — diluted $ (0.24 ) $ 0.53 $ 0.89 $ (1.95 )
Summary of NRG's outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company's diluted earnings per share	The following table summarizes NRG’s outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company’s diluted loss per share: Three months ended September 30, Nine months ended September 30, In millions of shares 2018 2017 2018 2017 Equity compensation plans 4 1 — 6 2048 Convertible Senior Notes 12 — 6 — Total 16 1 6 6

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The income tax provision consisted of the following: Three months ended September 30, Nine months ended September 30, In millions, except rates 2018 2017 2018 2017 Income before income taxes $ 313 $ 186 $ 620 $ 119 Income tax expense from continuing operations 7 1 19 3 Effective tax rate 2.2 % 0.5 % 3.1 % 2.5 %

Condensed Consolidating Finan_2

Condensed Consolidating Financial Information (Tables)	9 Months Ended
	Sep. 30, 2018
Condensed Consolidating Financial Information Disclosure [Abstract]
Condensed Consolidating Statements of Operations	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 2,618 $ 445 $ — $ (2 ) $ 3,061 Operating Costs and Expenses Cost of operations 2,005 295 9 (2 ) 2,307 Depreciation and amortization 67 36 9 — 112 Impairment losses — — — — — Selling, general and administrative 125 21 139 (73 ) 212 Reorganization costs — — 27 — 27 Development costs — (2 ) 3 — 1 Total operating costs and expenses 2,197 350 187 (75 ) 2,659 Gain on sale of assets — 14 — — 14 Operating Income/(Loss) 421 109 (187 ) 73 416 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 6 — 466 (472 ) — Equity in earnings of unconsolidated affiliates — 20 — — 20 Other income/(expense), net 4 8 5 — 17 Loss on debt extinguishment, net — (19 ) — (19 ) Interest expense (3 ) (8 ) (110 ) — (121 ) Total other income/(expense) 7 20 342 (472 ) (103 ) Income from Continuing Operations Before Income Taxes 428 129 155 (399 ) 313 Income tax expense/(benefit) 122 41 (156 ) — 7 Income from Continuing Operations 306 88 311 (399 ) 306 Income/(loss) from discontinued operations, net of income tax — 17 (371 ) — (354 ) Net Income/(Loss) 306 105 (60 ) (399 ) (48 ) Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests — (61 ) 12 73 24 Net Income/(Loss) Attributable to NRG Energy, Inc. common stockholders $ 306 $ 166 $ (72 ) $ (472 ) $ (72 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the nine months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 6,736 $ 1,072 $ — $ (13 ) $ 7,795 Operating Costs and Expenses Cost of operations 5,006 719 18 (13 ) 5,730 Depreciation and amortization 216 129 25 — 370 Impairment losses — 74 — — 74 Selling, general and administrative 337 46 282 (74 ) 591 Reorganization costs 4 — 66 — 70 Development costs — — 10 (1 ) 9 Total operating costs and expenses 5,563 968 401 (88 ) 6,844 Gain on sale of assets 3 27 — — 30 Operating Income/(Loss) 1,176 131 (401 ) 75 981 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 14 — 1,156 (1,170 ) — Equity in earnings/(losses) of unconsolidated affiliates — 27 (1 ) — 26 Other income/(expense), net 13 (27 ) 10 — (4 ) Loss on debt extinguishment, net — — (22 ) — (22 ) Interest expense (11 ) (42 ) (308 ) — (361 ) Total other income/(expense) 16 (42 ) 835 (1,170 ) (361 ) Income from Continuing Operations Before Income Taxes 1,192 89 434 (1,095 ) 620 Income tax expense/(benefit) 343 26 (350 ) — 19 Income from Continuing Operations 849 63 784 (1,095 ) 601 Income/(loss) from discontinued operations, net of income tax — 77 (397 ) — (320 ) Net Income 849 140 387 (1,095 ) 281 Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests — (181 ) 107 75 1 Net Income Attributable to NRG Energy, Inc. $ 849 $ 321 $ 280 $ (1,170 ) $ 280 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the three months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 2,366 $ 386 $ — $ (12 ) $ 2,740 Operating Costs and Expenses Cost of operations 1,826 239 18 (11 ) 2,072 Depreciation and amortization 100 55 8 — 163 Selling, general and administrative 106 16 69 (1 ) 190 Reorganization costs 2 (7 ) 17 — 12 Development costs — 1 5 — 6 Total operating costs and expenses 2,034 304 117 (12 ) 2,443 Operating Income/(Loss) 332 82 (117 ) — 297 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 7 — 459 (466 ) — Equity in earnings/(losses) of unconsolidated affiliates — 10 (1 ) — 9 Other income, net 7 38 8 (34 ) 19 Interest expense (4 ) (21 ) (114 ) — (139 ) Total other income/(expense) 10 27 352 (500 ) (111 ) Income from Continuing Operations Before Income Taxes 342 109 235 (500 ) 186 Income tax expense — — 1 — 1 Income from Continuing Operations 342 109 234 (500 ) 185 Income/(loss) from discontinued operations, net of income tax — 12 (34 ) — (22 ) Net Income 342 121 200 (500 ) 163 Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (3 ) 29 (34 ) (8 ) Net Income Attributable to NRG Energy, Inc. common stockholders $ 342 $ 124 $ 171 $ (466 ) $ 171 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS For the nine months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. Eliminations (a) Consolidated (In millions) Operating Revenues Total operating revenues $ 6,241 $ 1,042 $ — $ (37 ) $ 7,246 Operating Costs and Expenses Cost of operations 4,872 697 56 (36 ) 5,589 Depreciation and amortization 299 167 24 — — 490 Impairment losses 42 18 — — 60 Selling, general and administrative 309 55 — 271 (1 ) 634 Reorganization costs 2 (1 ) 17 — 18 Development costs — 4 14 — 18 Total operating costs and expenses 5,524 940 382 (37 ) 6,809 Other income - affiliate — — 87 — 87 Gain on sale of assets 4 — — — 4 Operating Income/(Loss) 721 102 (295 ) — 528 Other Income/(Expense) Equity in earnings of consolidated subsidiaries 20 — 738 (758 ) — Equity in (losses) of unconsolidated affiliates — (17 ) (3 ) — (20 ) Other income, net 7 82 23 (69 ) 43 Interest expense (11 ) (68 ) (353 ) — (432 ) Total other income/(expense) 16 (3 ) 405 (827 ) (409 ) Income from Continuing Operations Before Income Taxes 737 99 110 (827 ) 119 Income tax (benefit)/expense — (7 ) 10 — 3 Income from Continuing Operations 737 106 100 (827 ) 116 Loss from discontinued operations, net of income tax — (134 ) (664 ) — (798 ) Net Income/(Loss) 737 (28 ) (564 ) (827 ) (682 ) Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (49 ) 55 (69 ) (63 ) Net Income/(Loss) Attributable to NRG Energy, Inc. $ 737 $ 21 $ (619 ) $ (758 ) $ (619 ) (a) All significant intercompany transactions have been eliminated in consolidation.
Condensed Consolidating Statements of Comprehensive Income/(Loss)	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) For the three months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income $ 306 $ 105 $ (60 ) $ (399 ) $ (48 ) Other Comprehensive Income/(Loss), net of tax Unrealized gain/(loss) on derivatives, net — 10 (13 ) 7 4 Foreign currency translation adjustments, net (2 ) (2 ) (1 ) 3 (2 ) Defined benefit plans, net — — (1 ) — (1 ) Other comprehensive (loss)/income (2 ) 8 (15 ) 10 1 Comprehensive Income/(Loss) 304 113 (75 ) (389 ) (47 ) Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (58 ) 11 73 26 Comprehensive Income/(Loss) Attributable to NRG Energy, Inc. common stockholders $ 304 $ 171 $ (86 ) $ (462 ) $ (73 ) (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME For the nine months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net income $ 849 $ 140 $ 387 $ (1,095 ) $ 281 Other comprehensive (loss)/income, net of tax Unrealized gain on derivatives, net — 30 9 (15 ) 24 Foreign currency translation adjustments, net (8 ) (8 ) (9 ) 17 (8 ) Available-for-sale securities, net — — 1 — 1 Defined benefit plans, net — — (3 ) — (3 ) Other comprehensive (loss)/income (8 ) 22 (2 ) 2 14 Comprehensive income 841 162 385 (1,093 ) 295 Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (167 ) 107 75 15 Comprehensive income attributable to NRG Energy, Inc. $ 841 $ 329 $ 278 $ (1,168 ) $ 280 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME For the three months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Net Income $ 342 $ 121 $ 200 $ (500 ) $ 163 Other Comprehensive Income, net of tax Unrealized gain on derivatives, net 52 58 6 (109 ) 7 Foreign currency translation adjustments, net 1 1 4 (4 ) 2 Available-for-sale securities, net — — 1 — 1 Defined benefit plans, net 10 10 (1 ) (20 ) (1 ) Other comprehensive income 63 69 10 (133 ) 9 Comprehensive Income 405 190 210 (633 ) 172 Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (3 ) 32 (34 ) (5 ) Comprehensive Income Attributable to NRG Energy, Inc. common stockholders $ 405 $ 193 $ 178 $ (599 ) $ 177 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME/(LOSS) For the nine months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. Eliminations (a) Consolidated (In millions) Net income/(loss) $ 737 $ (28 ) $ (564 ) $ (827 ) $ (682 ) Other comprehensive income/(loss), net of tax Unrealized gain on derivatives, net 52 57 7 (109 ) 7 Foreign currency translation adjustments, net 6 6 10 (13 ) 9 Available-for-sale securities, net — — 2 — 2 Defined benefit plans, net 10 39 25 (49 ) 25 Other comprehensive income 68 102 44 (171 ) 43 Comprehensive income/(loss) 805 74 (520 ) (998 ) (639 ) Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest — (49 ) 57 (69 ) (61 ) Comprehensive income/(loss) Attributable to NRG Energy, Inc. $ 805 $ 123 $ (577 ) $ (929 ) $ (578 ) (a) All significant intercompany transactions have been eliminated in consolidation.
Condensed Consolidating Balance Sheets	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated ASSETS (In millions) Current Assets Cash and cash equivalents $ 130 $ 22 $ 1,207 $ — $ 1,359 Funds deposited by counterparties 30 — — — 30 Restricted cash 5 15 8 — 28 Accounts receivable, net 1,151 97 49 — 1,297 Inventory 301 107 — — 408 Derivative instruments 687 24 17 (45 ) 683 Deferred income tax 38 80 (118 ) — — Cash collateral paid in support of energy risk management activities 194 15 — — 209 Accounts receivable - affiliate 458 55 762 (1,256 ) 19 Prepayments and other current assets 160 35 53 — 248 Current assets - discontinued operations — 4 — — 4 Total current assets 3,154 454 1,978 (1,301 ) 4,285 Property, plant and equipment, net 2,372 1,077 150 — 3,599 Other Assets Investment in subsidiaries 477 — 4,379 (4,856 ) — Equity investments in affiliates — 452 — — 452 Notes receivable, less current portion — 10 12 (12 ) 10 Goodwill 359 180 — — 539 Intangible assets, net 403 199 — — 602 Nuclear decommissioning trust fund 719 — — — 719 Derivative instruments 357 9 36 (10 ) 392 Deferred income tax 34 (149 ) 126 — 11 Other non-current assets 92 70 119 — 281 Non-current assets - discontinued operations — 560 — — 560 Total other assets 2,441 1,331 4,672 (4,878 ) 3,566 Total Assets $ 7,967 $ 2,862 $ 6,800 $ (6,179 ) $ 11,450 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 89 $ 504 $ — $ 593 Accounts payable 705 55 64 — 824 Accounts payable — affiliate 1,610 (191 ) (148 ) (1,257 ) 14 Derivative instruments 565 30 — (45 ) 550 Deferred income taxes — 1 (1 ) — — Cash collateral received in support of energy risk management activities 30 — — — 30 Accrued expenses and other current liabilities 282 40 337 — 659 Accrued expenses and other current liabilities-affiliate — — 1 — 1 Current liabilities - discontinued operations — 52 — — 52 Total current liabilities 3,192 76 757 (1,302 ) 2,723 Other Liabilities Long-term debt and capital leases 244 244 6,182 (12 ) 6,658 Nuclear decommissioning reserve 278 — — — 278 Nuclear decommissioning trust liability 432 — — — 432 Deferred income taxes 112 62 (156 ) — 18 Derivative instruments 361 6 — (10 ) 357 Out-of-market contracts, net 54 123 — — 177 Other non-current liabilities 410 197 570 — 1,177 Non-current liabilities - discontinued operations — 547 — — 547 Total non-current liabilities 1,891 1,179 6,596 (22 ) 9,644 Total liabilities 5,083 1,255 7,353 (1,324 ) 12,367 Redeemable noncontrolling interest in subsidiaries — 19 — — 19 Stockholders’ Equity 2,884 1,588 (553 ) (4,855 ) (936 ) Total Liabilities and Stockholders’ Equity $ 7,967 $ 2,862 $ 6,800 $ (6,179 ) $ 11,450 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING BALANCE SHEETS December 31, 2017 Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (b) ASSETS (In millions) Current Assets Cash and cash equivalents $ — $ 124 $ 643 $ — $ 767 Funds deposited by counterparties 37 — — — 37 Restricted cash 4 275 — — 279 Accounts receivable, net 911 45 4 — 960 Inventory 338 148 — — 486 Derivative instruments 646 26 9 (57 ) 624 Cash collateral paid in support of energy risk management activities 170 1 — — 171 Accounts receivable - affiliate 685 183 (148 ) (534 ) 186 Prepayments and other current assets 122 30 27 — 179 Current assets held-for-sale 8 108 — — 116 Current assets - discontinued operations — 705 — — 705 Total current assets 2,921 1,645 535 (591 ) 4,510 Property, plant and equipment, net 2,507 3,695 237 (4 ) 6,435 Other Assets Investment in subsidiaries 266 — 7,581 (7,847 ) — Equity investments in affiliates — 180 2 — 182 Note receivable, less current portion — 2 — — — 2 Goodwill 360 179 — — 539 Intangible assets, net 455 55 — (3 ) 507 Nuclear decommissioning trust fund 692 — — — 692 Derivative instruments 126 — 2 31 — 159 Deferred income taxes 377 (135 ) (236 ) — 6 Other non-current assets 50 124 120 — 294 Non-current assets held for sale — 43 — — 43 Non-current assets - discontinued operations — 10,203 — (22 ) 10,181 Total other assets 2,326 10,653 7,498 (7,872 ) 12,605 Total Assets $ 7,754 $ 15,993 $ 8,270 $ (8,467 ) $ 23,550 LIABILITIES AND STOCKHOLDERS’ EQUITY Current Liabilities Current portion of long-term debt and capital leases $ — $ 183 $ 21 $ — $ 204 Accounts payable 609 47 55 — 711 Accounts payable — affiliate 742 (332 ) 181 (534 ) 57 Derivative instruments 556 38 — (57 ) 537 Cash collateral received in support of energy risk management activities 37 — — — 37 Accrued expenses and other current liabilities 304 64 401 — 769 Accrued expenses and other current liabilities - affiliate — — 161 — 161 Current liabilities held-for-sale — 72 — — 72 Current liabilities - discontinued operations — 859 5 — 864 Total current liabilities 2,248 931 824 (591 ) 3,412 Other Liabilities Long-term debt and capital leases 244 2,197 6,739 — 9,180 Nuclear decommissioning reserve 269 — — — 269 Nuclear decommissioning trust liability 415 — — — 415 Deferred income taxes 112 64 (155 ) — 21 Derivative instruments 136 7 — — 143 Out-of-market contracts, net 66 129 — — 195 Other non-current liabilities 410 201 391 — 1,002 Non-current liabilities held-for-sale — 8 — — 8 Non-current liabilities - discontinued operations — 6,859 — — 6,859 Total non-current liabilities 1,652 9,465 6,975 — 18,092 Total Liabilities 3,900 10,396 7,799 (591 ) 21,504 Redeemable noncontrolling interest in subsidiaries — 78 — — 78 Stockholders’ Equity 3,854 5,519 471 (7,876 ) 1,968 Total Liabilities and Stockholders’ Equity $ 7,754 $ 15,993 $ 8,270 $ (8,467 ) $ 23,550 (a) All significant intercompany transactions have been eliminated in consolidation. (b) Retrospectively adjusted as discussed in Note 1, Basis of Presentation .
Condensed Consolidating Statements of Cash Flows	NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the nine months ended September 30, 2018 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income $ 849 $ 140 $ 387 $ (1,095 ) $ 281 Loss from discontinued operations — 77 (397 ) — (320 ) Income from continuing operations 849 63 784 (1,095 ) 601 Adjustments to reconcile net income to net cash provided/(used) by operating activities: Distributions and equity in earnings of unconsolidated affiliates — 9 1 — 10 Depreciation, amortization and accretion 240 138 25 — 403 Provision for bad debts 55 2 — — 57 Amortization of nuclear fuel 38 — — — 38 Amortization of financing costs and debt discount/premiums — 5 16 — 21 Adjustment for debt extinguishment — — 22 — 22 Amortization of intangibles and out-of-market contracts 15 6 — — 21 Amortization of unearned equity compensation — — 36 — 36 Impairment losses — 89 — — 89 Changes in deferred income taxes and liability for uncertain tax benefits 343 11 (360 ) — (6 ) Changes in nuclear decommissioning trust liability 50 — — — 50 Changes in derivative instruments (38 ) 40 (4 ) (15 ) (17 ) Changes in collateral deposits in support of energy risk management activities (16 ) (14 ) — — (30 ) Gain on sale of emission allowances (20 ) — — — (20 ) Gain on sale of assets (3 ) (27 ) — — (30 ) GenOn settlement in July 2018 — — (125 ) — (125 ) Loss on deconsolidation of business — 13 — — 13 Changes in other working capital (567 ) (61 ) (857 ) 1,110 (375 ) Cash provided/(used) by continuing operations 946 274 (462 ) — 758 Cash provided by discontinued operations — 324 — — 324 Net Cash Provided/(Used) by Operating Activities 946 598 (462 ) — 1,082 Cash Flows from Investing Activities Acquisition of business, net of cash acquired (2 ) (207 ) — — (209 ) Capital expenditures (158 ) (150 ) — (37 ) — (345 ) Purchases of emission allowances (30 ) — — — (30 ) Proceeds from sale of emission allowances 54 — — — 54 Investments in nuclear decommissioning trust fund securities (449 ) — — — (449 ) Proceeds from the sale of nuclear decommissioning trust fund securities 398 — — — 398 Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees 10 8 1,537 — 1,555 Deconsolidation of business — (268 ) — — (268 ) Change in investments in unconsolidated affiliates — (62 ) — — (62 ) Cash (used)/provided by continuing operations (177 ) (679 ) 1,500 — 644 Cash used by discontinued operations — (703 ) (703 ) Net Cash (Used)/Provided by Investing Activities (177 ) (1,382 ) 1,500 — (59 ) Cash Flows from Financing Activities Payments (for)/from intercompany loans (645 ) (12 ) 657 — — Payment of dividends to common stockholders — — (28 ) — (28 ) Payment for treasury stock — — (1,000 ) — (1,000 ) Proceeds from issuance of long-term debt — 163 832 — 995 Payments for short and long-term debt — (106 ) (864 ) — (970 ) Receivable from affiliate — — (26 ) (26 ) Net distributions to noncontrolling interests in subsidiaries — (17 ) — — (17 ) Payment of debt issuance costs — — (19 ) — (19 ) Other — (4 ) — — (4 ) Cash provided/(used) by continuing operations (645 ) 24 (448 ) — (1,069 ) Cash provided by discontinued operations — 403 — — 403 Net Cash Provided/(Used) by Financing Activities (645 ) 427 (448 ) — (666 ) Effect of exchange rate changes on cash and cash equivalents — 1 — — 1 Change in cash from discontinued operations — 24 — — 24 Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash 124 (380 ) 590 — 334 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 41 399 643 — 1,083 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 165 $ 19 $ 1,233 $ — $ 1,417 (a) All significant intercompany transactions have been eliminated in consolidation. NRG ENERGY, INC. AND SUBSIDIARIES CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS For the nine months ended September 30, 2017 (Unaudited) Guarantor Subsidiaries Non-Guarantor Subsidiaries NRG Energy, Inc. (Note Issuer) Eliminations (a) Consolidated (In millions) Cash Flows from Operating Activities Net income/(loss) $ 737 $ (28 ) $ (564 ) $ (827 ) $ (682 ) Loss from discontinued operations — (134 ) (664 ) — (798 ) Income from continuing operations 737 106 100 (827 ) 116 Adjustments to reconcile net income to net cash provided/(used) by operating activities: Distributions and equity in earnings of unconsolidated affiliates — (65 ) 3 62 — Depreciation, amortization and accretion 299 167 24 — 490 Provision for bad debts 42 — 15 — 57 Amortization of nuclear fuel 37 — — — 37 Amortization of financing costs and debt discount/premiums — 2 13 — 15 Adjustment for debt extinguishment — 3 — — 3 Amortization of intangibles and out-of-market contracts 20 59 — — 79 Amortization of unearned equity compensation — — 27 — 27 Impairment losses 42 18 — — 60 Changes in deferred income taxes and liability for uncertain tax benefits — (7 ) 6 — (1 ) Changes in nuclear decommissioning trust liability 20 — — — 20 Changes in derivative instruments (11 ) 43 12 (8 ) 36 Changes in collateral deposits in support of energy risk management activities (126 ) 23 — — (103 ) Proceeds from sale of emission allowances 21 — — — 21 Gain on sale of assets (4 ) — — — (4 ) Changes in other working capital (1,035 ) (484 ) 451 773 (295 ) Cash provided/(used) by continuing operations 42 (135 ) 651 — 558 Cash provided by discontinued operations — 178 — — 178 Net Cash Provided by Operating Activities 42 43 651 — 736 Cash Flows from Investing Activities Intercompany dividends — — 129 (129 ) — Acquisition of businesses, net of cash acquired — (12 ) — — (12 ) Capital expenditures (135 ) (18 ) (19 ) — (172 ) Purchases of emission allowances (47 ) — — — (47 ) Proceeds from sale of emission allowances 105 (1 ) — — 104 Investments in nuclear decommissioning trust fund securities (402 ) — — — (402 ) Proceeds from the sale of nuclear decommissioning trust fund securities 382 — — — 382 Proceeds from sale of assets, net of cash disposed of 36 — 273 — 309 Change in investments in unconsolidated affiliates — 24 — — 24 Other 30 — — — 30 Cash (used)/provided by continuing operations (31 ) (7 ) 383 (129 ) 216 Cash used by discontinued operations — (638 ) — — (638 ) Net Cash (Used)/Provided by Investing Activities (31 ) (645 ) 383 (129 ) (422 ) Cash Flows from Financing Activities Payments (for)/from intercompany loans 9 417 (426 ) — — Intercompany dividends — (129 ) — 129 — Payment of dividends to common stockholders — — (28 ) — (28 ) Net receipts from settlement of acquired derivatives that include financing elements — — — — — Proceeds from issuance of long-term debt — 94 214 — 308 Payments for short and long-term debt — (124 ) (219 ) — (343 ) Increase in notes receivable from affiliate — (125 ) — — (125 ) Net distributions to noncontrolling interests from subsidiaries — (18 ) — — (18 ) Payments of debt issuance costs — (34 ) (5 ) — (39 ) Other — (8 ) — — (8 ) Cash provided/(used) by continuing operations 9 73 (464 ) 129 (253 ) Cash provided by discontinued operations — 39 — — 39 Net Cash Provided/(Used) by Financing Activities 9 112 (464 ) 129 (214 ) Effect of exchange rate changes on cash and cash equivalents — (10 ) — — (10 ) Change in cash from discontinued operations — (421 ) — — (421 ) Net Increase/(Decrease) in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash 20 (79 ) 570 — 511 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period 3 534 323 — 860 Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period $ 23 $ 455 $ 893 $ — $ 1,371 (a) All significant intercompany transactions have been eliminated in consolidation.

Basis of Presentation - Basis o

Basis of Presentation - Basis of Presentation (Details) MW in Thousands	Sep. 30, 2018MW
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Generation capacity (in MW)	26

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Other Balance Sheet Information (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accounts receivable allowance for doubtful accounts	$ 37	$ 28
Property, plant and equipment accumulated depreciation	2,652	3,013
Intangible assets accumulated amortization	1,194	1,572
Out-of-market contracts accumulated amortization	$ 372	$ 354

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 1,359	$ 767	$ 1,022	$ 591
Funds deposited by counterparties	30	37	31	2
Restricted cash	28	279	318	267
Cash and cash equivalents, funds deposited by counterparties and restricted cash shown in the statement of cash flows	$ 1,417	$ 1,083	$ 1,371	$ 860

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Pension and Postretirement Benefit Plan Amendments (Details) - Scenario, Forecast $ in Millions	3 Months Ended
	Dec. 31, 2018USD ($)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Loss related to curtailment	$ 17
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Gain from benefit plan amendment and remeasurement	$ 2

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Noncontrolling Interest (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Noncontrolling Interest [Roll Forward]
Balance as of beginning of period	$ 2,314
Dividends paid to NRG Yield, Inc. public shareholders	(61)
Distributions to noncontrolling interest	(43)
Net income attributable to noncontrolling interest - continuing operations	5
Net income attributable to noncontrolling interest - discontinued operations	21
Other comprehensive income attributable to noncontrolling interest - discontinued operations	14
Contributions from noncontrolling interest	296
Sale of assets to NRG Yield, Inc.	(8)
Balance as of end of period	0
Noncontrolling Interest
Noncontrolling Interest [Roll Forward]
Non-cash adjustments to noncontrolling interest	10
Agua Caliente
Noncontrolling Interest [Roll Forward]
Deconsolidation	(279)
NRG Yield and Renewables
Noncontrolling Interest [Roll Forward]
Deconsolidation	(2,180)
Ivampah
Noncontrolling Interest [Roll Forward]
Deconsolidation	$ (89)

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Redeemable Noncontrolling Interest (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Noncontrolling Interest [Line Items]
Balance as of beginning of period	$ 78
Distributions to noncontrolling interest	(43)
Contributions from redeemable noncontrolling interest	26
Net income attributable to redeemable noncontrolling interest - continuing operations	5
Net income attributable to redeemable noncontrolling interest - discontinued operations	21
Balance as of end of period	19
Redeemable Noncontrolling Interest
Noncontrolling Interest [Line Items]
Distributions to noncontrolling interest	(3)
Non-cash adjustments to noncontrolling interest	(9)
Net income attributable to redeemable noncontrolling interest - continuing operations	1
Net income attributable to redeemable noncontrolling interest - discontinued operations	(26)
NRG Yield and Renewables
Noncontrolling Interest [Line Items]
Deconsolidation of NRG Yield and Renewables Platform	(2,180)
NRG Yield and Renewables | Redeemable Noncontrolling Interest
Noncontrolling Interest [Line Items]
Deconsolidation of NRG Yield and Renewables Platform	$ (48)

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to opening retained earnings	$ (6,001)		$ (6,269)
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to opening retained earnings		$ 16

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Capacity Revenue (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from External Customer [Line Items]
Estimated revenue for cleared auction MWs, capacity auctions	$ 2,075	$ 5,766
Capacity revenue
Revenue from External Customer [Line Items]
Estimated revenue for cleared auction MWs, capacity auctions	$ 254	$ 688
Scenario, Forecast | Capacity revenue
Revenue from External Customer [Line Items]
Estimated revenue for cleared auction MWs, capacity auctions			$ 244	$ 528	$ 459	$ 610	$ 152

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2,075		$ 5,766
Mark-to-market for economic hedging activities	(69)	$ (28)	62	$ 9
Contract amortization	5		12
Operating revenues	3,061	2,740	7,795	7,246
Lease revenue	6		16
Derivative revenue	(65)	(33)	79	2
Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(480)		(918)
Contract amortization	0		0
Operating revenues	(722)	(509)	(928)	(924)
Lease revenue	0		0
Energy revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	479		1,403
Derivative revenue	871		1,884
Energy revenue | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(479)		(890)
Derivative revenue	0		0
Capacity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	254		688
Derivative revenue	45		110
Capacity revenue | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1		0
Derivative revenue	0		0
Retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Retail revenue | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Retail revenue | Mass customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,766		4,317
Retail revenue | Mass customers | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(2)		(4)
Retail revenue | Business Solutions customers
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	434		1,181
Retail revenue | Business Solutions customers | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Total retail revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,200		5,498
Total retail revenue | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(2)		(4)
Derivative revenue
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	55		(31)
Derivative revenue	975		2,001
Derivative revenue | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	(241)		(21)
Derivative revenue	(241)		0
Other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	68		225
Other revenue | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		(3)
Total operating revenue
Disaggregation of Revenue [Line Items]
Operating revenues	3,061		7,795
Total operating revenue | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(721)		(918)
Other revenue, derivative
Disaggregation of Revenue [Line Items]
Derivative revenue	4		17
Other revenue, derivative | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Derivative revenue	0		0
Retail | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,199		5,492
Contract amortization	0		0
Operating revenues	2,203	1,936	5,497	4,868
Lease revenue	3		10
Retail | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(1)	(3)	(7)	(3)
Retail | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Derivative revenue	0		0
Retail | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Derivative revenue	0		0
Retail | Retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Retail | Retail revenue | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,768		4,321
Retail | Retail revenue | Business Solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	434		1,181
Retail | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,202		5,502
Retail | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	1		(5)
Derivative revenue	1		(5)
Retail | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Retail | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	2,203		5,497
Retail | Other revenue, derivative | Operating Segments
Disaggregation of Revenue [Line Items]
Lease revenue	3
Derivative revenue	0		0
Generation | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	356		1,192
Contract amortization	5		12
Operating revenues	1,579	1,313	3,216	3,289
Lease revenue	3		6
Generation | Corporate/Eliminations
Disaggregation of Revenue [Line Items]
Operating revenues	(740)	$ (493)	(944)	$ (872)
Generation | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	958		2,293
Derivative revenue	871		1,884
Generation | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	253		688
Derivative revenue	45		110
Generation | Retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Generation | Retail revenue | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | Retail revenue | Business Solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	295		(5)
Derivative revenue	1,215		2,006
Generation | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	68		228
Generation | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	1,579		3,216
Generation | Other revenue, derivative | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	4		17
Generation | Gulf Coast | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	(110)		45
Contract amortization	5		12
Lease revenue	0		0
Generation | Gulf Coast | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	680		1,558
Derivative revenue	896		1,877
Generation | Gulf Coast | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	66		201
Derivative revenue	0		0
Generation | Gulf Coast | Retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Generation | Gulf Coast | Retail revenue | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | Gulf Coast | Retail revenue | Business Solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | Gulf Coast | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | Gulf Coast | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	268		(7)
Derivative revenue	1,160		1,871
Generation | Gulf Coast | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	36		164
Generation | Gulf Coast | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	1,055		1,928
Generation | Gulf Coast | Other revenue, derivative | Operating Segments
Disaggregation of Revenue [Line Items]
Derivative revenue	(4)		1
Generation | East/West/Other | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	466		1,147
Contract amortization	0		0
Lease revenue	3		6
Generation | East/West/Other | Energy revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	278		735
Derivative revenue	(25)		7
Generation | East/West/Other | Capacity revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	187		487
Derivative revenue	45		110
Generation | East/West/Other | Retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Generation | East/West/Other | Retail revenue | Mass customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | East/West/Other | Retail revenue | Business Solutions customers | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | East/West/Other | Total retail revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0		0
Generation | East/West/Other | Derivative revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Mark-to-market for economic hedging activities	27		2
Derivative revenue	55		135
Generation | East/West/Other | Other revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	32		64
Generation | East/West/Other | Total operating revenue | Operating Segments
Disaggregation of Revenue [Line Items]
Operating revenues	524		1,288
Generation | East/West/Other | Other revenue, derivative | Operating Segments
Disaggregation of Revenue [Line Items]
Lease revenue	3
Derivative revenue	$ 8		$ 16

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Lease Revenue (Details)	Sep. 30, 2018
Accounting Policies [Abstract]
Operating lease, term	20 years

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Contract Assets and Liabilities (Details) $ in Millions	Sep. 30, 2018USD ($)
Schedule Of Contract Assets And Liabilities [Line Items]
Deferred customer acquisition costs	$ 104
Total accounts receivable, net	1,297
Unbilled revenues (included within Accounts receivable, net - Contracts with customers)	385
Deferred revenues	60
Accounts receivable, net - Contracts with customers
Schedule Of Contract Assets And Liabilities [Line Items]
Total accounts receivable, net	1,265
Accounts receivable, net - Derivative instruments
Schedule Of Contract Assets And Liabilities [Line Items]
Total accounts receivable, net	$ 32

Summary of Significant Accou_14

Summary of Significant Accounting Policies - Recent Accounting Developments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of operations	$ 2,307	$ 2,072	$ 5,730	$ 5,589
Other income, net	$ 17	19	$ (4)	43
ASU 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of operations		4		13
Other income, net		$ 0		$ 0

Acquisitions, Discontinued Op_3

Acquisitions, Discontinued Operations and Dispositions - Acquisitions (Details) customer in Thousands, $ in Millions	Jun. 01, 2018USD ($)statecustomer	Oct. 31, 2018USD ($)customer
XOOM Energy, LLC
Business Acquisition [Line Items]
Number of states in which acquisition operates | state	19
Purchase price	$ 219
Payments for estimated working capital included	$ 54
Increase in customers in retail portfolio | customer	300
Purchase price allocated to accounts receivable	$ 45
Purchase price allocated to derivative assets	42
Purchase price allocated to current and non-current assets	26
Purchase price allocated to accounts payable	25
Purchase price allocated to derivative liabilities	31
Purchase price allocated to current and non-current liabilities	18
XOOM Energy, LLC | Customer Relationships And Contracts
Business Acquisition [Line Items]
Purchase price allocated to finite-lived intangible assets	170
XOOM Energy, LLC | Cash
Business Acquisition [Line Items]
Purchase price allocated to cash	2
XOOM Energy, LLC | Restricted Cash
Business Acquisition [Line Items]
Purchase price allocated to cash	$ 8
Subsequent Event | Small Book Acquisitions
Business Acquisition [Line Items]
Purchase price		$ 44
Increase in customers in retail portfolio | customer		115

Acquisitions, Discontinued Op_4

Acquisitions, Discontinued Operations and Dispositions - Discontinued Operations (Details) $ in Millions	Aug. 31, 2018USD ($)	Feb. 06, 2018USD ($)extension	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other non-current liabilities			$ 1,177		$ 1,177		$ 1,002
Loss from discontinued operations			354	$ 22	320	$ 798
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Commitment and advisory fees	$ 50
NRG Yield and Renewables | Agua Caliente solar project
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest prior to disposal	51.00%
Ownership interest after disposal	35.00%
Gain on sale	$ 8
NRG Yield and Renewables | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration	1,348
NRG Yield and Renewables | Discontinued Operations | Scenario, Adjustment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other non-current liabilities	$ (153)
Loss from discontinued operations		$ 153
Carlsbad Energy Holdings LLC | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration		$ 365
Loss from discontinued operations			$ 354	$ (5)	$ 295	$ (4)
Membership interest		100.00%
Lease and easement agreement, number of extensions | extension		2
Lease, renewal term		10 years
Other project commitments		$ 23

Acquisitions, Discontinued Op_5

Acquisitions, Discontinued Operations and Dispositions - Summarized of Results of Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on deconsolidation, net of tax			$ (13)	$ 0
Gain/(Loss) from discontinued operations, net of tax	$ (354)	$ (22)	(320)	(798)
Discontinued Operations | Carlsbad Energy Holdings LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues	280	315	925	906
Operating costs and expenses	(212)	(242)	(682)	(690)
Other expenses	(44)	(64)	(165)	(210)
Gain/(loss) from operations of discontinued components, before tax	24	9	78	6
Income tax expense	9	4	4	2
Loss from discontinued operations, net of tax	15	5	74	4
Loss on deconsolidation, net of tax	(139)	0	(139)	0
California property tax indemnification	(153)	0	(153)	0
Other	(77)	0	(77)	0
Loss on disposal of discontinued operations, net of tax	(369)	0	(369)	0
Gain/(Loss) from discontinued operations, net of tax	(354)	5	(295)	4
Discontinued Operations | GenOn
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues	0	0	0	646
Operating costs and expenses	0	0	0	(700)
Other expenses	0	0	0	(98)
Gain/(loss) from operations of discontinued components, before tax	0	0	0	(152)
Income tax expense	0	0	0	9
Loss from discontinued operations	0	0	0	(161)
Interest income - affiliate	0	0	3	6
Loss from discontinued operations, net of tax	0	0	3	(155)
Pre-tax loss on deconsolidation	0	0	0	(208)
Settlement consideration and services credit	0	0	1	(289)
Pension and post-retirement liability assumption	0	(25)	(2)	(144)
Other	0	(2)	(27)	(6)
Loss on disposal of discontinued operations, net of tax	0	(27)	(28)	(647)
Gain/(Loss) from discontinued operations, net of tax	$ 0	$ (27)	$ (25)	$ (802)

Acquisitions, Discontinued Op_6

Acquisitions, Discontinued Operations and Dispositions - Major Classes of Assets and Liabilities Classified as Discontinued Operations (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other current assets	$ 0	$ 116
Current assets - discontinued operations	4	705
Other non-current assets	0	43
Non-current assets - discontinued operations	560	10,181
Current liabilities - discontinued operations	52	864
Other non-current liabilities	0	8
Non-current liabilities - discontinued operations	547	6,859
Carlsbad Project | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	0
Restricted Cash	0
Accounts receivable, net	0
Other current assets	4
Current assets - discontinued operations	4
Property, plant and equipment, net	547
Equity investments in affiliates	0
Intangible assets, net	8
Other non-current assets	5
Non-current assets - discontinued operations	560
Current portion of long term debt and capital leases	14
Accounts payable	37
Other current liabilities	1
Current liabilities - discontinued operations	52
Long-term debt and capital leases	545
Other non-current liabilities	2
Non-current liabilities - discontinued operations	$ 547
Renewables And Carlsbad Project | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents		224
Restricted Cash		229
Accounts receivable, net		119
Other current assets		133
Current assets - discontinued operations		705
Property, plant and equipment, net		7,473
Equity investments in affiliates		856
Intangible assets, net		1,240
Other non-current assets		612
Non-current assets - discontinued operations		10,181
Current portion of long term debt and capital leases		484
Accounts payable		169
Other current liabilities		211
Current liabilities - discontinued operations		864
Long-term debt and capital leases		6,673
Other non-current liabilities		186
Non-current liabilities - discontinued operations		$ 6,859

Acquisitions, Discontinued Op_7

Acquisitions, Discontinued Operations and Dispositions - Sale of Assets to NRG Yield, Inc. Prior to Discontinued Operations (Details) $ in Millions	Sep. 30, 2018MW	Jun. 19, 2018USD ($)	Mar. 30, 2018USD ($)MW	Mar. 27, 2017USD ($)MW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generation capacity (in MW) | MW	26,000
UPMC Thermal Project
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration		$ 84
Buckthorn Renewables, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration			$ 42
Percentage of ownership sold			100.00%
Generation capacity (in MW) | MW			154
Assumed non-recourse debt in transaction			$ 183
Agua Caliente solar project
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash consideration				$ 130
Assumed non-recourse debt in transaction				328
Working capital adjustments				$ 1
Agua Caliente solar project | Agua Caliente
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of ownership sold				16.00%
Generation capacity (in MW) | MW				46
Agua Caliente solar project | Utah Portfolio
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generation capacity (in MW) | MW				265
Number of utility scale solar projects | MW				7

Acquisitions, Discontinued Op_8

Acquisitions, Discontinued Operations and Dispositions - Gen On and GenMA Settlement (Details) - USD ($) $ in Millions	Jul. 16, 2018	Apr. 27, 2018	Dec. 31, 2017	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pension liability					$ 76
Liability, other postretirement-employment and retiree heal and welfare benefits					25
GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Settlement consideration	$ 261				$ 261.3
Professional fees		$ 6
GenOn Entities | Services Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Credit applied						$ 28
Shared services, annualized rate			$ 84			84
GenOn Entities | Assignment Of Historical Claims Against REMA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining payments and other balances due	8
GenOn Entities | Reduction Of Settlement Payment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining payments and other balances due	4.2
GenOn Entities | Indemnification Of Potential Claims By REMA (up to)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining payments and other balances due	10
Plan of Reorganization
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of aggregate principal amount					93.00%
Payment of pension contributions			13			13
Plan of Reorganization | GenOn Mid-Atlantic | Intercompany Credit Agreement | Letter of Credit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Letters of credit		$ 37.5
Plan of Reorganization | Services Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Credit applied						28
Payment to affiliate					$ 18
Shared services, annualized rate			84			$ 84
Plan of Reorganization | Services Agreement | GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payment to affiliate	15		$ 15	$ 13.5
Plan of Reorganization | GenOn Entities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to affiliate, settlement agreement	125
Plan of Reorganization | GenOn Entities | Services Agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Credit applied	28
Remaining payments and other balances due	10
Plan of Reorganization | GenOn Entities | Revolving Credit Facility Borrowings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Intercompany secured revolving credit facility and accrued interest and fees	151
Plan of Reorganization | GenOn Entities | Accrued Interest On Borrowings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Intercompany secured revolving credit facility and accrued interest and fees	12
Plan of Reorganization | GenOn Entities | Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining payments and other balances due	$ 6

Acquisitions, Discontinued Op_9

Acquisitions, Discontinued Operations and Dispositions - Dispositions (Details) $ in Millions	Nov. 01, 2018USD ($)MW	Aug. 01, 2018USD ($)	Jun. 29, 2018USD ($)	Jun. 28, 2018USD ($)	Sep. 30, 2018USD ($)MW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generation capacity (in MW) | MW					26,000
Agua Caliente Borrower 1, LLC | Subsequent Event | Scenario, Forecast | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of ownership interest	$ 120
Generation capacity (in MW) | MW	290
BETM | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of ownership sold		100.00%
Proceeds from sale, net of working capital adjustments		$ 71
Gain on sale		15
Cash collateral		4
BETM | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations | Letter of Credit
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Guarantee obligations		119
BETM | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations | Guarantee, other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Guarantee obligations		$ 32
Canal 3 | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale			$ 17
Cash proceeds from sale			$ 16
Proceeds from financing arrangements				$ 167
Proceeds from financing distributed to the company				$ 151
Other | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds from sale					$ 12
Clearway Energy, Inc. | Agua Caliente Borrower 1, LLC | Subsequent Event | Scenario, Forecast | Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage by noncontrolling owner	35.00%

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Estimated Carrying Amounts and Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term debt, including current portion	$ 7,436	$ 9,494
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes receivable	11	2
Long-term debt, including current portion	7,331	9,482
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes receivable	8	2
Long-term debt, including current portion	7,653	9,739
Fair Value | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term debt, including current portion	7,385	7,432
Fair Value | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term debt, including current portion	$ 268	$ 2,307

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Assets and Liabilities Measured and Recorded at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 1,022	$ 744
Derivative liabilities	905	674
Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	53	39
Derivative liabilities	2	6
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	21	22
U.S. government and federal agency obligations	1	1
Total assets	1,816	1,498
Derivative liabilities	907	680
Fair value, measurements, recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1,022	744
Derivative liabilities	905	674
Fair value, measurements, recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	53	39
Derivative liabilities	2	6
Fair value, measurements, recurring | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	21	47
Fair value, measurements, recurring | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	41	43
Fair value, measurements, recurring | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	88	82
Fair value, measurements, recurring | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	19	14
Fair value, measurements, recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	112	99
Fair value, measurements, recurring | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	368	334
Equity contracts	66	68
Fair value, measurements, recurring | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	4	5
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	2	3
U.S. government and federal agency obligations	1	1
Total assets	643	616
Derivative liabilities	271	257
Fair value, measurements, recurring | Level 1 | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	210	191
Derivative liabilities	271	257
Fair value, measurements, recurring | Level 1 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair value, measurements, recurring | Level 1 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	21	45
Fair value, measurements, recurring | Level 1 | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	41	42
Fair value, measurements, recurring | Level 1 | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 1 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 1 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	368	334
Fair value, measurements, recurring | Level 1 | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	0	0
U.S. government and federal agency obligations	0	0
Total assets	1,019	751
Derivative liabilities	554	364
Fair value, measurements, recurring | Level 2 | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	743	509
Derivative liabilities	552	358
Fair value, measurements, recurring | Level 2 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	53	39
Derivative liabilities	2	6
Fair value, measurements, recurring | Level 2 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	2
Fair value, measurements, recurring | Level 2 | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	1
Fair value, measurements, recurring | Level 2 | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	88	82
Fair value, measurements, recurring | Level 2 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	19	14
Fair value, measurements, recurring | Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	112	99
Fair value, measurements, recurring | Level 2 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 2 | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	4	5
Fair value, measurements, recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in securities (classified within other non-current assets)	19	19
U.S. government and federal agency obligations	0	0
Total assets	88	63
Derivative liabilities	82	59
Fair value, measurements, recurring | Level 3 | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	69	44
Derivative liabilities	82	59
Fair value, measurements, recurring | Level 3 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair value, measurements, recurring | Level 3 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | U.S. government and federal agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Federal agency mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	0	0
Fair value, measurements, recurring | Level 3 | Foreign government fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear trust fund investments	$ 0	$ 0

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Reconciliation of Level 3 Financial Instruments (Details) - Level 3 - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 193	$ 9	$ 4	$ (47)
Contracts acquired in Xoom acquisition	0		12
Total gains/(losses)— realized/unrealized included in earnings	0	(31)	(15)	14
Purchases	12	(9)	9	0
Transfers into Level 3	(201)	(7)	(4)	(11)
Transfers out of Level 3	2	7	0	13
Ending balance	6	(31)	6	(31)
Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held	(3)	(16)	(18)	(12)
Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	19	18	19	17
Contracts acquired in Xoom acquisition	0		0
Total gains/(losses)— realized/unrealized included in earnings	0	1	0	2
Purchases	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending balance	19	19	19	19
Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held	0	0	0	0
Derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	174	(9)	(15)	(64)
Contracts acquired in Xoom acquisition	0		12
Total gains/(losses)— realized/unrealized included in earnings	0	(32)	(15)	12
Purchases	12	(9)	9	0
Transfers into Level 3	(201)	(7)	(4)	(11)
Transfers out of Level 3	2	7	0	13
Ending balance	(13)	(50)	(13)	(50)
Losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets or liabilities still held	$ (3)	$ (16)	$ (18)	$ (12)

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Derivative Fair Value Measurements, Narrative (Details)	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Total derivative assets valued with prices provided by models and other valuation techniques (as a percent)	6.00%
Total derivative liabilities valued with prices provided by models and other valuation techniques (as a percent)	9.00%

Fair Value of Financial Instr_7

Fair Value of Financial Instruments - Derivative Fair Value Measurements (Details) $ in Millions	Sep. 30, 2018USD ($)$ / MWh	Dec. 31, 2017USD ($)$ / MWh
Fair value, measurements, recurring
Liabilities
Derivative liabilities	$ 907	$ 680
Fair value, measurements, recurring | Level 3
Liabilities
Derivative liabilities	82	59
Commodity contracts
Assets
Derivative assets	1,022	744
Liabilities
Derivative liabilities	905	674
Commodity contracts | Fair value, measurements, recurring
Assets
Derivative assets	1,022	744
Liabilities
Derivative liabilities	905	674
Commodity contracts | Fair value, measurements, recurring | Level 3
Assets
Derivative assets	69	44
Liabilities
Derivative liabilities	82	59
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts
Assets
Derivative assets	44	33
Liabilities
Derivative liabilities	$ 68	$ 47
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts | Low
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	2	10
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts | High
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	197	142
Commodity contracts | Fair value, measurements, recurring | Level 3 | Power Contracts | Weighted Average
Fair Value Inputs / Range
Forward Market Price (per MWh) | $ / MWh	23	24
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs
Assets
Derivative assets	$ 25	$ 11
Liabilities
Derivative liabilities	$ 14	$ 12
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs | Low
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	(90)	(28)
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs | High
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	86	46
Commodity contracts | Fair value, measurements, recurring | Level 3 | FTRs | Weighted Average
Fair Value Inputs / Range
Auction Prices (per MWh) | $ / MWh	0	0

Fair Value of Financial Instr_8

Fair Value of Financial Instruments - Counterparty Credit Risk (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Concentration of Credit Risk
Counterparty credit exposure to a portion of the Company's counterparties	$ 290
Net counterparty credit exposure to a portion of the Company's counterparties	251
Collateral held (cash and letters of credit) against counterparty credit exposure to a portion of the Company's counterparties	$ 48
Company's exposure before collateral is expected to roll off by the end of 2019 (as a percent)	76.00%
Net exposure (as a percent)	100.00%
Counterparty credit risk exposure to certain counterparties, threshold (as a percent)	10.00%
Aggregate counterparty credit risk exposure for counterparties representing exposure above threshold percentage	$ 60
Estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements for the next 5 years	$ 1,500
Period of estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements (in years)	5 years
Investment grade
Concentration of Credit Risk
Net exposure (as a percent)	59.00%
Non-Investment grade/Non-Rated
Concentration of Credit Risk
Net exposure (as a percent)	41.00%
Utilities, energy merchants, marketers and other
Concentration of Credit Risk
Net exposure (as a percent)	83.00%
Financial institutions
Concentration of Credit Risk
Net exposure (as a percent)	17.00%

Nuclear Decommissioning Trust_3

Nuclear Decommissioning Trust Fund - Summary of aggregate fair values and realized gains and losses (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Nuclear decommissioning trust fund
Fair Value	$ 719	$ 692
Unrealized Gains	298	276
Unrealized Losses	7	2
Cash and cash equivalents
Nuclear decommissioning trust fund
Fair Value	21	47
Unrealized Gains	0	0
Unrealized Losses	0	0
U.S. government and federal agency obligations
Nuclear decommissioning trust fund
Fair Value	41	43
Unrealized Gains	1	1
Unrealized Losses	$ 1	$ 0
Weighted-average Maturities (In years)	12 years	11 years
Federal agency mortgage-backed securities
Nuclear decommissioning trust fund
Fair Value	$ 88	$ 82
Unrealized Gains	0	1
Unrealized Losses	$ 3	$ 1
Weighted-average Maturities (In years)	23 years	23 years
Commercial mortgage-backed securities
Nuclear decommissioning trust fund
Fair Value	$ 19	$ 14
Unrealized Gains	0	0
Unrealized Losses	$ 1	$ 0
Weighted-average Maturities (In years)	22 years	20 years
Corporate debt securities
Nuclear decommissioning trust fund
Fair Value	$ 112	$ 99
Unrealized Gains	1	2
Unrealized Losses	$ 2	$ 1
Weighted-average Maturities (In years)	10 years	11 years
Equity securities
Nuclear decommissioning trust fund
Fair Value	$ 434	$ 402
Unrealized Gains	296	272
Unrealized Losses	0	0
Foreign government fixed income securities
Nuclear decommissioning trust fund
Fair Value	4	5
Unrealized Gains	0	0
Unrealized Losses	$ 0	$ 0
Weighted-average Maturities (In years)	9 years	9 years

Nuclear Decommissioning Trust_4

Nuclear Decommissioning Trust Fund - Summary of proceeds from sales of available-for-sale securities and related gains and losses (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Nuclear Decommissioning Trust Fund Disclosure [Abstract]
Realized gains	$ 8	$ 8
Realized losses	8	6
Proceeds from sale of securities	$ 398	$ 382

Accounting for Derivative Ins_3

Accounting for Derivative Instruments and Hedging Activities - Net notional volume buy/sell of open derivative transactions (Details) shares in Millions, mw_per_day in Millions, T in Millions, MWh in Millions, MMBTU in Millions, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018USD ($)MWhMMBTUmw_per_dayTshares	Dec. 31, 2017USD ($)MWhMMBTUmw_per_dayTshares
Long | Emissions
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, mass (ton) | T	3	1
Long | Renewable Energy Certificates
Volumetric Underlying Derivative Transactions
Derivative, non-monetary notional amount (in shares) | shares	1	0
Long | Coal
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, mass (ton) | T	8	21
Long | Power
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, energy (in MMBtu and MWh) | MWh	8	23
Long | Interest
Volumetric Underlying Derivative Transactions
Derivative, notional amount (in usd) | $	$ 1,058	$ 1,060
Long | Equity
Volumetric Underlying Derivative Transactions
Derivative, non-monetary notional amount (in shares) | shares	0	1
Short | Natural Gas
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, energy (in MMBtu and MWh) | MMBTU	439	20
Short | Capacity
Volumetric Underlying Derivative Transactions
Derivative, nonmonetary notional amount, flow rate (in MW/Day) | mw_per_day	(1)	(1)

Accounting for Derivative Ins_4

Accounting for Derivative Instruments and Hedging Activities - Fair value within the derivative instrument valuation (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Assets	$ 1,075	$ 783
Derivative Liabilities	907	680
Interest rate contracts current
Derivative [Line Items]
Derivative Assets	17	8
Derivative Liabilities	0	1
Interest rate contracts long-term
Derivative [Line Items]
Derivative Assets	36	31
Derivative Liabilities	2	5
Commodity contracts current
Derivative [Line Items]
Derivative Assets	666	616
Derivative Liabilities	550	536
Commodity contracts long-term
Derivative [Line Items]
Derivative Assets	356	128
Derivative Liabilities	$ 355	$ 138

Accounting for Derivative Ins_5

Accounting for Derivative Instruments and Hedging Activities - Offsetting of derivatives by counterparty master agreement level and collateral received (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Cash Collateral (Held) / Posted	$ (30)	$ (37)
Cash Collateral Posted	209	171
Gross Amounts of Recognized Assets / Liabilities	168	103
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	12	61
Net Amount	180	164
Commodity contracts
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative assets	1,022	744
Derivative Instruments	(765)	(578)
Cash Collateral (Held) / Posted	(18)	(11)
Net Amount	239	155
Derivative liabilities	(905)	(674)
Derivative Instruments	765	578
Cash Collateral Posted	30	72
Net Amount	(110)	(24)
Gross Amounts of Recognized Assets / Liabilities	117	70
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	12	61
Net Amount	129	131
Interest rate contracts
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative assets	53	39
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	0	0
Net Amount	53	39
Derivative liabilities	(2)	(6)
Derivative Instruments	0	0
Cash Collateral Posted	0	0
Net Amount	(2)	(6)
Gross Amounts of Recognized Assets / Liabilities	51	33
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	0	0
Net Amount	$ 51	$ 33

Accounting for Derivative Ins_6

Accounting for Derivative Instruments and Hedging Activities - Effect of ASC 815 on accumulated OCI balance attributable to hedge derivatives, net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassified from accumulated OCI to income:
Sale of NRG Yield and the Renewables Platform	$ 25	$ 0	$ 25	$ 0
Accumulated other comprehensive income (loss), tax	0	15	0	15
Interest rate contracts
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax
Accumulated OCI beginning balance	(23)	(67)	(54)	(66)
Reclassified from accumulated OCI to income:
Due to realization of previously deferred amounts	1	4	8	10
Mark-to-market of cash flow hedge accounting contracts	(3)	4	21	(3)
Accumulated OCI ending balance, net of $0, and $15 tax	$ 0	$ (59)	$ 0	$ (59)

Accounting for Derivative Ins_7

Accounting for Derivative Instruments and Hedging Activities - Pre-tax effects of economic hedges not designated a cash flow hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Unrealized mark-to-market results
Reversal of previously recognized unrealized (gains)/losses on settled positions related to economic hedges	$ (84)	$ (7)	$ (85)	$ 18
Reversal of acquired gain positions related to economic hedges	(10)	(2)	(11)	(1)
Net unrealized gains/(losses) on open positions related to economic hedges	25	(19)	158	(8)
Total unrealized mark-to-market (losses)/gains for economic hedging activities	(69)	(28)	62	9
Reversal of previously recognized unrealized gains on settled positions related to trading activity	(4)	(5)	(10)	(24)
Net unrealized gains on open positions related to trading activity	8	0	27	17
Total unrealized mark-to-market gains/(losses) for trading activity	4	(5)	17	(7)
Total unrealized (losses)/gains	(65)	(33)	79	2
Credit Risk Related Contingent Features
Unrealized gain (loss) from open economic hedge positions			158	(8)
Collateral due on net liability position that has not been called by a certain marginable agreement counterparty	6		6
Adequate Assurance Clauses
Credit Risk Related Contingent Features
Derivative net liability position, collateral required Contracts with Credit Rating Contingent Feature	25		25
Credit Rating Contingent Features
Credit Risk Related Contingent Features
Derivative net liability position, collateral required Contracts with Credit Rating Contingent Feature	17		17
Commodity contracts
Unrealized mark-to-market results
Total unrealized (losses)/gains	(65)	(33)	79	2
Commodity contracts | Operating revenues
Unrealized mark-to-market results
Total unrealized (losses)/gains	59	17	(14)	170
Commodity contracts | Cost of operations
Unrealized mark-to-market results
Total unrealized (losses)/gains	(124)	(50)	93	(168)
Interest rate contracts
Unrealized mark-to-market results
Total unrealized (losses)/gains	$ 2	$ 3	$ 17	$ (4)

Impairments (Details)

Impairments (Details) - USD ($)	Jun. 29, 2018	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Impaired Long-Lived Assets Held and Used [Line Items]
Carrying amount of related assets		$ 452,000,000				$ 452,000,000		$ 182,000,000
Impairment losses		$ 0		$ 0		$ 74,000,000	$ 60,000,000
Construction in progress					$ 0
Renewables
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment losses							$ 19,000,000
Construction in Progress
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment losses					$ 41,000,000
Keystone
Impaired Long-Lived Assets Held and Used [Line Items]
Ownership interest	3.70%
Impairment losses to reduce carrying amounts	$ 14,000,000
Conemaugh
Impaired Long-Lived Assets Held and Used [Line Items]
Ownership interest	3.70%
Impairment losses to reduce carrying amounts	$ 14,000,000
Dunkirk
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment losses to reduce carrying amounts			$ 46,000,000
Carrying amount of related assets			$ 0

Debt and Capital Leases - Sched

Debt and Capital Leases - Schedule of Long-term Debt and Capital Leases (Details) - USD ($) $ in Millions	Mar. 21, 2018	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt amount		$ 7,436	$ 9,494
Capital leases		2	5
Subtotal long-term debt and capital leases (including current maturities)		7,438	9,499
Current portion of long-term debt and capital leases		(593)	(204)
Less debt issuance costs		(82)	(103)
Discounts		(105)	(12)
Long-term debt and capital leases		6,658	9,180
Recourse Debt
Debt Instrument [Line Items]
Debt amount		7,167	7,182
Recourse Debt | Senior Notes, due 2022
Debt Instrument [Line Items]
Debt amount		$ 485	992
Interest rate, stated percentage		6.25%
Recourse Debt | Senior Notes, due 2024
Debt Instrument [Line Items]
Debt amount		$ 733	733
Interest rate, stated percentage		6.25%
Recourse Debt | Senior Notes, due 2026
Debt Instrument [Line Items]
Debt amount		$ 1,000	1,000
Interest rate, stated percentage		7.25%
Recourse Debt | Senior Notes, due 2027
Debt Instrument [Line Items]
Debt amount		$ 1,230	1,250
Interest rate, stated percentage		6.625%
Recourse Debt | Senior Notes, due 2028
Debt Instrument [Line Items]
Debt amount		$ 821	870
Interest rate, stated percentage		5.75%
Recourse Debt | Convertible Senior Notes, due 2048
Debt Instrument [Line Items]
Debt amount		$ 575	0
Interest rate, stated percentage		2.75%
Recourse Debt | Term loan facility, due 2023
Debt Instrument [Line Items]
Debt amount		$ 1,857	1,872
Recourse Debt | Term loan facility, due 2023 | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.75%	1.75%
Recourse Debt | Tax-exempt bonds
Debt Instrument [Line Items]
Debt amount		$ 466	465
Recourse Debt | Tax-exempt bonds | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		4.125%
Recourse Debt | Tax-exempt bonds | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		6.00%
Non Recourse Debt
Debt Instrument [Line Items]
Debt amount		$ 269	2,312
Non Recourse Debt | Ivanpah, due 2033 and 2038
Debt Instrument [Line Items]
Debt amount		$ 0	1,073
Non Recourse Debt | Ivanpah, due 2033 and 2038 | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		2.285%
Non Recourse Debt | Ivanpah, due 2033 and 2038 | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		4.256%
Non Recourse Debt | Agua Caliente, due 2037
Debt Instrument [Line Items]
Debt amount		$ 0	818
Non Recourse Debt | Agua Caliente, due 2037 | Minimum
Debt Instrument [Line Items]
Interest rate, stated percentage		2.395%
Non Recourse Debt | Agua Caliente, due 2037 | Maximum
Debt Instrument [Line Items]
Interest rate, stated percentage		3.633%
Non Recourse Debt | Agua Caliente Borrower 1, due 2038
Debt Instrument [Line Items]
Debt amount		$ 86	89
Interest rate, stated percentage		5.43%
Non Recourse Debt | Midwest Generation, due 2019
Debt Instrument [Line Items]
Debt amount		$ 78	152
Interest rate, stated percentage		4.39%
Non Recourse Debt | Other
Debt Instrument [Line Items]
Debt amount		$ 105	$ 180

Debt and Capital Leases - Narra

Debt and Capital Leases - Narrative (Details) - USD ($) $ in Millions	Mar. 21, 2018	Sep. 30, 2018	Nov. 05, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt amount		$ 7,436		$ 9,494
Recourse Debt
Debt Instrument [Line Items]
Debt amount		7,167		7,182
Term loan facility, due 2023 | Recourse Debt
Debt Instrument [Line Items]
Debt amount		$ 1,857		$ 1,872
Term loan facility, due 2023 | Recourse Debt | Subsequent Event
Debt Instrument [Line Items]
Prepaid amount of Term Loans			$ 155
Debt amount			260
Term loan facility, due 2023 | Recourse Debt | LIBOR
Debt Instrument [Line Items]
Change in interest rate	0.50%
Basis spread on variable rate	1.75%	1.75%
Term loan facility, due 2023 | Recourse Debt | LIBOR floor
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
Term loan facility, due 2023 | Senior Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Debt amount			$ 105

Debt and Capital Leases - Conve

Debt and Capital Leases - Convertible Senior Notes (Details)	3 Months Ended
	Jun. 30, 2018USD ($)$ / shares
Debt Instrument [Line Items]
Transaction costs in connection with issuance	$ 12,000,000
Convertible Senior Notes, due 2048 | Convertible Debt
Debt Instrument [Line Items]
Aggregate principal amount	$ 575,000,000
Interest rate, stated percentage	2.75%
Conversion price (in usd per share) | $ / shares	$ 47.74
Conversion ratio	20.9479
Carrying amount of liability component	$ 472,000,000
Carrying amount of equity component	$ 103,000,000
Debt discount amortization period (years)	7 years
Deferred financing costs, amortization period	7 years
Convertible Senior Notes, due 2048 | Convertible Debt | Additional Paid-in Capital
Debt Instrument [Line Items]
Transaction costs in connection with issuance	$ 2,000,000
Convertible Senior Notes, due 2048 | Convertible Debt | Deferred Financing Costs
Debt Instrument [Line Items]
Transaction costs in connection with issuance	$ 10,000,000

Debt and Capital Leases - Senio

Debt and Capital Leases - Senior Notes Repurchased (Details) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Nov. 05, 2018USD ($)	Oct. 09, 2018USD ($)
Debt Instrument, Redemption [Line Items]
Loss on debt extinguishment, net	$ 19		$ 0	$ 22	$ 0
Senior Notes
Debt Instrument, Redemption [Line Items]
Loss on debt extinguishment, net				22
Write-off of deferred financing costs				$ 6
Recourse Debt | 5.750% senior notes due 2028
Debt Instrument, Redemption [Line Items]
Interest rate, stated percentage	5.75%			5.75%
Principal amount repurchased	$ 20	$ 29		$ 20
Cash Paid	$ 20	$ 30		$ 20
Average Early Redemption Percentage	99.13%	99.24%
Recourse Debt | 6.250% senior notes due 2022
Debt Instrument, Redemption [Line Items]
Interest rate, stated percentage	6.25%			6.25%
Principal amount repurchased	$ 492	$ 14		$ 492
Cash Paid	$ 512	$ 15		512
Average Early Redemption Percentage	103.13%	103.25%
Partial redemption	$ 486
Recourse Debt | Senior Notes
Debt Instrument, Redemption [Line Items]
Principal amount repurchased	575	$ 43		575
Cash Paid	598	$ 45		598
Accrued interest	$ 7			$ 7
Recourse Debt | 6.625% senior notes due 2027
Debt Instrument, Redemption [Line Items]
Interest rate, stated percentage	6.625%			6.625%
Principal amount repurchased	$ 20			$ 20
Cash Paid	$ 21			21
Average Early Redemption Percentage	103.06%
Transformation Plan
Debt Instrument, Redemption [Line Items]
Partial redemption				$ 640
Target net debt to EBITDA credit ratio				3
Subsequent Event | Recourse Debt | 6.250% senior notes due 2022
Debt Instrument, Redemption [Line Items]
Interest rate, stated percentage							6.25%
Principal amount repurchased							$ 485
Subsequent Event | Recourse Debt | Term loan facility, due 2023
Debt Instrument, Redemption [Line Items]
Cash Paid						$ 155

Variable Interest Entities, o_3

Variable Interest Entities, or VIEs (Details) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2018USD ($)	Sep. 30, 2018USD ($)projectMW	Dec. 31, 2017USD ($)
Investments Accounted for by the Equity Method
Generation capacity (in MW) | MW		26,000
Loss on deconsolidation and subsequent recognition		$ 22
Equity investments in affiliates		452	$ 182
Current assets		6	6
Net property, plant and equipment		76	80
Other long-term assets		31	36
Total assets		113	122
Current liabilities		2	3
Long-term debt		29	30
Other long-term liabilities		8	7
Total liabilities		39	40
Redeemable noncontrolling interest		19	19
Net assets less noncontrolling interests		$ 55	$ 63
Ivampah Master Holdings LLC
Investments Accounted for by the Equity Method
Economic interest in equity method investments (as a percent)		54.60%
Number of solar electric generating projects | project		3
Generation capacity (in MW) | MW		392
Release of reserve funds	$ (95)
Deconsolidation reduced the Company's assets		$ 1,300
Deconsolidation reduced the Company's liabilities		1,200
Equity investments in affiliates		$ 45

Changes in Capital Structure -

Changes in Capital Structure - Narrative (Details) - USD ($)	Sep. 05, 2018	May 24, 2018	Jan. 01, 2018	Jul. 31, 2018	Jan. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018	Feb. 28, 2018	Dec. 31, 2017
Capital Structure
Common stock, shares authorized (in shares)						500,000,000			500,000,000		500,000,000
Shares issued under ESPP (in shares)			175,862		175,862
Stock repurchase program, authorized amount	$ 500,000,000	$ 354,000,000
Total number of shares purchased (in shares)									28,544,693
Commissions per share (in dollars per share)						$ 0.01			$ 0.01
Shares repurchased (in shares)	12,820,512,000,000						9,969,023
Treasury
Capital Structure
Shares issued under ESPP (in shares)			175,862
Total number of shares purchased (in shares)									28,544,693
Accelerated Share Repurchase Program
Capital Structure
Shares repurchased (in shares)				860,880
Value of shares received	$ 452,000,000	343,000,000
Average price paid per share under ASR Agreement (in dollars per share)				$ 32.69
Accelerated Share Repurchase Program | Additional Paid-in Capital
Capital Structure
Remaining amount recorded in additional paid in capital	48,000,000	$ 11,000,000
Accelerated Share Repurchase Program | Treasury
Capital Structure
Remaining amount recorded in additional paid in capital				$ 11,000,000
Capital Allocation Plan
Capital Structure
Stock repurchase program, authorized amount	$ 1,000,000,000					$ 1,000,000,000			$ 1,000,000,000	$ 1,000,000,000
Total number of shares purchased (in shares)						13,681,392	11,748,553	3,114,748	28,544,693
Amounts paid for shares purchased						$ 500,000,000	$ 407,000,000	$ 93,000,000	$ 1,000,000,000

Changes in Capital Structure _2

Changes in Capital Structure - Changes in NRG's common shares outstanding and issued (Details) - shares	Jan. 01, 2018	Jan. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2018
Schedule of Stock by Class, Equity [Roll Forward]
Balance as of beginning of period (in shares)	418,323,134	418,323,134			418,323,134	418,323,134
Treasury shares, balance as of beginning of period (in shares)	(101,580,045)	(101,580,045)			(101,580,045)	(101,580,045)
Outstanding, as of beginning of period (in shares)	316,743,089	316,743,089			316,743,089	316,743,089
Shares issued under LTIPs						1,555,766
Shares issued under ESPP	175,862	175,862
Shares repurchased						(28,544,693)
Balance as of end of period (in shares)			419,878,900			419,878,900
Treasury shares, balance as of end of the period (in shares)			(129,948,876)			(129,948,876)
Outstanding, as of end of period (in shares)			289,930,024			289,930,024
Issued
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs						1,555,766
Shares issued under ESPP	0
Shares repurchased						0
Treasury
Schedule of Stock by Class, Equity [Roll Forward]
Shares issued under LTIPs						0
Shares issued under ESPP	175,862
Shares repurchased						(28,544,693)
Capital Allocation Plan
Schedule of Stock by Class, Equity [Roll Forward]
Shares repurchased			(13,681,392)	(11,748,553)	(3,114,748)	(28,544,693)

Changes in Capital Structure _3

Changes in Capital Structure - Schedule of dividends paid (Details) - $ / shares	Oct. 17, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Dividends [Abstract]
Dividends Per Common Share (in usd per share)		$ 0.03	$ 0.03	$ 0.03	$ 0.03	$ 0.09	$ 0.09
Subsequent Event
Subsequent Event [Line Items]
Common stock dividends declared (in usd per share)	$ 0.03
Common stock dividends proposed annual amount (in usd per share)	$ 0.12

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information
Total operating revenues	$ 3,061	$ 2,740	$ 7,795	$ 7,246
Depreciation and amortization	112	163	370	490
Impairment losses	0	0	74	60
Reorganization costs	27	12	70	18
Gain on sale of assets	14		30	4
Equity in earnings of unconsolidated affiliates	20	9	26	(20)
Loss on debt extinguishment, net	(19)	0	(22)	0
(Loss)/income from continuing operations before income taxes	313	186	620	119
(Loss)/income from continuing operations	306	185	601	116
Income/(Loss) from discontinued operations, net of income tax	(354)	(22)	(320)	(798)
Net (Loss)/Income	(48)	163	281	(682)
(Loss)/Income attributable to NRG Energy, Inc. common stockholders	(72)	171	280	(619)
Total assets	11,450		11,450		$ 23,550
Eliminations
Segment Reporting Information
Total operating revenues	(722)	(509)	(928)	(924)
Depreciation and amortization	2	(1)	0	(2)
Impairment losses			0	0
Reorganization costs	0	0	0	0
Gain on sale of assets	0		0	0
Equity in earnings of unconsolidated affiliates	(2)	(3)	(5)	(5)
Loss on debt extinguishment, net	0		0
(Loss)/income from continuing operations before income taxes	(504)	(1)	(1,228)	(4)
(Loss)/income from continuing operations	(504)	(1)	(1,228)	(4)
Income/(Loss) from discontinued operations, net of income tax	0	0	0	0
Net (Loss)/Income	(504)	(1)	(1,228)	(4)
(Loss)/Income attributable to NRG Energy, Inc. common stockholders	(501)	2	(1,224)	1
Total assets	(6,693)		(6,693)
Retail | Operating Segments
Segment Reporting Information
Total operating revenues	2,203	1,936	5,497	4,868
Depreciation and amortization	30	28	86	81
Impairment losses			0	0
Reorganization costs	6	5	10	5
Gain on sale of assets	0		0	0
Equity in earnings of unconsolidated affiliates	0	0	0	0
Loss on debt extinguishment, net	0		0
(Loss)/income from continuing operations before income taxes	(127)	72	733	371
(Loss)/income from continuing operations	(127)	72	733	380
Income/(Loss) from discontinued operations, net of income tax	0	0	0	0
Net (Loss)/Income	(127)	72	733	380
(Loss)/Income attributable to NRG Energy, Inc. common stockholders	(127)	72	732	380
Total assets	3,465		3,465
Retail | Eliminations
Segment Reporting Information
Total operating revenues	(1)	(3)	(7)	(3)
Generation | Operating Segments
Segment Reporting Information
Total operating revenues	1,579	1,313	3,216	3,289
Depreciation and amortization	73	128	259	385
Impairment losses			74	60
Reorganization costs	3	3	10	3
Gain on sale of assets	0		1	4
Equity in earnings of unconsolidated affiliates	20	9	27	(21)
Loss on debt extinguishment, net	0		0
(Loss)/income from continuing operations before income taxes	595	272	303	185
(Loss)/income from continuing operations	595	272	302	183
Income/(Loss) from discontinued operations, net of income tax	0	0	0	0
Net (Loss)/Income	595	272	302	183
(Loss)/Income attributable to NRG Energy, Inc. common stockholders	579	256	293	169
Total assets	6,699		6,699
Generation | Eliminations
Segment Reporting Information
Total operating revenues	(740)	(493)	(944)	(872)
Corporate | Operating Segments
Segment Reporting Information
Total operating revenues	1	0	10	13
Depreciation and amortization	7	8	25	26
Impairment losses			0	0
Reorganization costs	18	4	50	10
Gain on sale of assets	14		29	0
Equity in earnings of unconsolidated affiliates	2	3	4	6
Loss on debt extinguishment, net	(19)		(22)
(Loss)/income from continuing operations before income taxes	349	(157)	812	(433)
(Loss)/income from continuing operations	342	(158)	794	(443)
Income/(Loss) from discontinued operations, net of income tax	(354)	(22)	(320)	(798)
Net (Loss)/Income	(12)	(180)	474	(1,241)
(Loss)/Income attributable to NRG Energy, Inc. common stockholders	(23)	(159)	479	(1,169)
Total assets	7,979		7,979
Corporate | Eliminations
Segment Reporting Information
Total operating revenues	$ 19	$ (13)	$ 23	$ (49)

Earnings_(Loss) Per Share - Rec

Earnings/(Loss) Per Share - Reconciliation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic income/(loss) per share attributable to NRG Energy, Inc. common stockholders
Net (loss)/income attributable to NRG Energy, Inc. common stockholders	$ (72)	$ 171	$ 280	$ (619)
Weighted average number of common shares outstanding — basic (in shares)	299	317	309	317
(Loss)/Earnings per Weighted Average Common Share — Basic (in usd per share)	$ (0.24)	$ 0.54	$ 0.91	$ (1.95)
Diluted income/(loss) per share attributable to NRG Energy, Inc. common stockholders
Weighted average number of common shares outstanding - diluted (in shares)	299	317	309	317
Incremental shares attributable to the issuance of equity compensation (treasury stock method) (in shares)	0	5	4	0
Total dilutive shares (in shares)	299	322	313	317
(Loss)/Earnings per weighted average common share — diluted (in usd per share)	$ (0.24)	$ 0.53	$ 0.89	$ (1.95)

Earnings_(Loss) Per Share - Ant

Earnings/(Loss) Per Share - Anti-dilutive Securities (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	16	1	6	6
Equity compensation plans
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	4	1	0	6
2048 Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	12	0	6	0

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Effective Tax Rate
Income before income taxes	$ 313	$ 186	$ 620	$ 119
Income tax expense from continuing operations	$ 7	$ 1	$ 19	$ 3
Effective tax rate	2.20%	0.50%	3.10%	2.50%
Uncertain Tax Benefits
Non-current tax liability for uncertain tax benefits	$ 47		$ 47
Accrued interest related to unrecognized tax benefits	2		2
Uncertain tax benefits, penalties and interest accrued	$ 5		$ 5

Related Party Transactions - Se

Related Party Transactions - Service Agreement and Transition Services Agreement with GenOn (Details) - USD ($) $ in Millions	Jul. 16, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Services Agreement | Restructuring Support Agreement
Related Party Transaction [Line Items]
Shared services, annualized rate						$ 84
Credit applied						28
GenOn | Services Agreement
Related Party Transaction [Line Items]
Shared services, annualized rate						84
Credit applied						$ 28
GenOn | Services Agreement | Restructuring Support Agreement
Related Party Transaction [Line Items]
Credit applied	$ 28
GenOn | Transition Services Agreement | Restructuring Support Agreement
Related Party Transaction [Line Items]
Selling, general and administrative expenses		$ 18		$ 53
Other income related to services			$ 14		$ 104
GenOn | Management Service | Services Agreement
Related Party Transaction [Line Items]
Service fees				$ 193

Related Party Transactions - Cr

Related Party Transactions - Credit Agreement with GenOn (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Amount outstanding	$ 7,436,000,000	$ 9,494,000,000
Cash collateral paid in support of energy risk management activities	209,000,000	171,000,000
GenOn
Related Party Transaction [Line Items]
Cash collateral paid in support of energy risk management activities	15,000,000	32,000,000
GenOn | Revolving Credit Facility | Intercompany Credit Agreement
Related Party Transaction [Line Items]
Credit facility maximum borrowing capacity	500,000,000
Letters of credit outstanding under revolver	30,000,000	92,000,000
Amount outstanding	$ 0	$ 125,000,000

Commitments and Contingencies (

Commitments and Contingencies (Details)	Mar. 27, 2018USD ($)	Feb. 26, 2018USD ($)case	Feb. 16, 2018USD ($)	Sep. 07, 2017USD ($)	Jun. 01, 2001	May 31, 2016lawsuit	Sep. 30, 2018USD ($)lawsuit	Aug. 18, 2016USD ($)
Midwest Generation Asbestos Liabilities
Loss Contingencies
Damages sought, amount	$ 61,000,000
Telephone Consumer Protection Act Purported Class Actions
Loss Contingencies
Damages sought, amount							$ 1,500
Number of lawsuits/cases | lawsuit							3
Telephone Consumer Protection Act Purported Class Actions | California
Loss Contingencies
Number of lawsuits/cases | lawsuit							1
Telephone Consumer Protection Act Purported Class Actions | New Jersey
Loss Contingencies
Number of lawsuits/cases | lawsuit							2
CDWR and SDGE v Sunrise Power
Loss Contingencies
Damages sought, amount							$ 1,200,000
PPA period					10 years
Remaining term							70 months
BTEC New Albany v. NRG Texas Power LLC
Loss Contingencies
Damages sought, amount				$ 48,000,000
Natural Gas Litigation
Loss Contingencies
Damages sought, amount		$ 0
Number of lawsuits/cases		4				4
Natixis V. GenOn Mid-Atlantic
Loss Contingencies
Damages sought, amount			$ 34,000,000
Lignite Contract With Texas Westmoreland Coal Co.
Loss Contingencies
Bond obligation								$ 99,000,000

Condensed Consolidating Finan_3

Condensed Consolidating Financial Information - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Amount outstanding	$ 7,436	$ 9,494
Recourse Debt
Debt Instrument [Line Items]
Amount outstanding	7,167	$ 7,182
Senior Notes | Recourse Debt
Debt Instrument [Line Items]
Amount outstanding	$ 4,800

Condensed Consolidating Finan_4

Condensed Consolidating Financial Information - STATEMENTS OF OPERATIONS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating Revenues
Total operating revenues	$ 3,061	$ 2,740	$ 7,795	$ 7,246
Operating Costs and Expenses
Cost of operations	2,307	2,072	5,730	5,589
Depreciation and amortization	112	163	370	490
Impairment losses	0	0	74	60
Selling, general and administrative	212	190	591	634
Reorganization costs	27	12	70	18
Development costs	1	6	9	18
Total operating costs and expenses	2,659	2,443	6,844	6,809
Other income - affiliate	0	0	0	87
Gain on sale of assets	14	0	30	4
Operating Income/(Loss)	416	297	981	528
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	0	0	0	0
Equity in earnings/(losses) of unconsolidated affiliates	20	9	26	(20)
Other income/(expense), net	17	19	(4)	43
Loss on debt extinguishment, net	(19)	0	(22)	0
Interest expense	(121)	(139)	(361)	(432)
Total other income/(expense)	(103)	(111)	(361)	(409)
Income from Continuing Operations Before Income Taxes	313	186	620	119
Income tax expense/(benefit)	7	1	19	3
Income from Continuing Operations	306	185	601	116
Income/(Loss) from discontinued operations, net of income tax	(354)	(22)	(320)	(798)
Net (Loss)/Income	(48)	163	281	(682)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	24	(8)	1	(63)
Net (Loss)/Income Attributable to NRG Energy, Inc. common stockholders	(72)	171	280	(619)
Eliminations
Operating Revenues
Total operating revenues	(2)	(12)	(13)	(37)
Operating Costs and Expenses
Cost of operations	(2)	(11)	(13)	(36)
Depreciation and amortization	0	0	0	0
Impairment losses	0		0	0
Selling, general and administrative	(73)	(1)	(74)	(1)
Reorganization costs	0	0	0
Development costs	0	0	(1)	0
Total operating costs and expenses	(75)	(12)	(88)	(37)
Other income - affiliate				0
Gain on sale of assets	0		0	0
Operating Income/(Loss)	73	0	75	0
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	(472)	(466)	(1,170)	(758)
Equity in earnings/(losses) of unconsolidated affiliates	0	0	0	0
Other income/(expense), net	0	(34)	0	(69)
Loss on debt extinguishment, net	0		0
Interest expense	0	0	0	0
Total other income/(expense)	(472)	(500)	(1,170)	(827)
Income from Continuing Operations Before Income Taxes	(399)	(500)	(1,095)	(827)
Income tax expense/(benefit)	0	0	0	0
Income from Continuing Operations	(399)	(500)	(1,095)	(827)
Income/(Loss) from discontinued operations, net of income tax	0	0	0	0
Net (Loss)/Income	(399)	(500)	(1,095)	(827)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	73	(34)	75	(69)
Net (Loss)/Income Attributable to NRG Energy, Inc. common stockholders	(472)	(466)	(1,170)	(758)
Guarantor Subsidiaries
Operating Revenues
Total operating revenues	2,618	2,366	6,736	6,241
Operating Costs and Expenses
Cost of operations	2,005	1,826	5,006	4,872
Depreciation and amortization	67	100	216	299
Impairment losses	0		0	42
Selling, general and administrative	125	106	337	309
Reorganization costs	0	2	4
Development costs	0	0	0	0
Total operating costs and expenses	2,197	2,034	5,563	5,524
Other income - affiliate				0
Gain on sale of assets	0		3	4
Operating Income/(Loss)	421	332	1,176	721
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	6	7	14	20
Equity in earnings/(losses) of unconsolidated affiliates	0	0	0	0
Other income/(expense), net	4	7	13	7
Loss on debt extinguishment, net	0		0
Interest expense	(3)	(4)	(11)	(11)
Total other income/(expense)	7	10	16	16
Income from Continuing Operations Before Income Taxes	428	342	1,192	737
Income tax expense/(benefit)	122	0	343	0
Income from Continuing Operations	306	342	849	737
Income/(Loss) from discontinued operations, net of income tax	0	0	0	0
Net (Loss)/Income	306	342	849	737
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	0	0	0	0
Net (Loss)/Income Attributable to NRG Energy, Inc. common stockholders	306	342	849	737
Non-Guarantor Subsidiaries
Operating Revenues
Total operating revenues	445	386	1,072	1,042
Operating Costs and Expenses
Cost of operations	295	239	719	697
Depreciation and amortization	36	55	129	167
Impairment losses	0		74	18
Selling, general and administrative	21	16	46	55
Reorganization costs	0	(7)	0
Development costs	(2)	1	0	4
Total operating costs and expenses	350	304	968	940
Other income - affiliate				0
Gain on sale of assets	14		27	0
Operating Income/(Loss)	109	82	131	102
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	0	0	0	0
Equity in earnings/(losses) of unconsolidated affiliates	20	10	27	(17)
Other income/(expense), net	8	38	(27)	82
Loss on debt extinguishment, net			0
Interest expense	(8)	(21)	(42)	(68)
Total other income/(expense)	20	27	(42)	(3)
Income from Continuing Operations Before Income Taxes	129	109	89	99
Income tax expense/(benefit)	41	0	26	(7)
Income from Continuing Operations	88	109	63	106
Income/(Loss) from discontinued operations, net of income tax	17	12	77	(134)
Net (Loss)/Income	105	121	140	(28)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	(61)	(3)	(181)	(49)
Net (Loss)/Income Attributable to NRG Energy, Inc. common stockholders	166	124	321	21
NRG Energy, Inc. (Note Issuer)
Operating Revenues
Total operating revenues	0	0	0	0
Operating Costs and Expenses
Cost of operations	9	18	18	56
Depreciation and amortization	9	8	25	24
Impairment losses	0		0	0
Selling, general and administrative	139	69	282	271
Reorganization costs	27	17	66
Development costs	3	5	10	14
Total operating costs and expenses	187	117	401	382
Other income - affiliate				87
Gain on sale of assets	0		0	0
Operating Income/(Loss)	(187)	(117)	(401)	(295)
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	466	459	1,156	738
Equity in earnings/(losses) of unconsolidated affiliates	0	(1)	(1)	(3)
Other income/(expense), net	5	8	10	23
Loss on debt extinguishment, net	(19)		(22)
Interest expense	(110)	(114)	(308)	(353)
Total other income/(expense)	342	352	835	405
Income from Continuing Operations Before Income Taxes	155	235	434	110
Income tax expense/(benefit)	(156)	1	(350)	10
Income from Continuing Operations	311	234	784	100
Income/(Loss) from discontinued operations, net of income tax	(371)	(34)	(397)	(664)
Net (Loss)/Income	(60)	200	387	(564)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interests	12	29	107	55
Net (Loss)/Income Attributable to NRG Energy, Inc. common stockholders	$ (72)	$ 171	$ 280	$ (619)

Condensed Consolidating Finan_5

Condensed Consolidating Financial Information - COMPREHENSIVE INCOME/(LOSS) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Condensed Financial Statements, Captions [Line Items]
Net Income	$ (48)	$ 163	$ 281	$ (682)
Other Comprehensive Income/(Loss), net of tax
Unrealized gain/(loss) on derivatives, net	4	7	24	7
Foreign currency translation adjustments, net	(2)	2	(8)	9
Available-for-sale securities, net	0	1	1	2
Defined benefit plans, net	(1)	(1)	(3)	25
Other comprehensive income	1	9	14	43
Comprehensive (loss) income	(47)	172	295	(639)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	26	(5)	15	(61)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	(73)	177	280	(578)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net Income	(399)	(500)	(1,095)	(827)
Other Comprehensive Income/(Loss), net of tax
Unrealized gain/(loss) on derivatives, net	7	(109)	(15)	(109)
Foreign currency translation adjustments, net	3	(4)	17	(13)
Available-for-sale securities, net		0	0	0
Defined benefit plans, net	0	(20)	0	(49)
Other comprehensive income	10	(133)	2	(171)
Comprehensive (loss) income	(389)	(633)	(1,093)	(998)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	73	(34)	75	(69)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	(462)	(599)	(1,168)	(929)
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Income	306	342	849	737
Other Comprehensive Income/(Loss), net of tax
Unrealized gain/(loss) on derivatives, net	0	52	0	52
Foreign currency translation adjustments, net	(2)	1	(8)	6
Available-for-sale securities, net		0	0	0
Defined benefit plans, net	0	10	0	10
Other comprehensive income	(2)	63	(8)	68
Comprehensive (loss) income	304	405	841	805
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	0	0	0	0
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	304	405	841	805
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Income	105	121	140	(28)
Other Comprehensive Income/(Loss), net of tax
Unrealized gain/(loss) on derivatives, net	10	58	30	57
Foreign currency translation adjustments, net	(2)	1	(8)	6
Available-for-sale securities, net		0	0	0
Defined benefit plans, net	0	10	0	39
Other comprehensive income	8	69	22	102
Comprehensive (loss) income	113	190	162	74
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	(58)	(3)	(167)	(49)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	171	193	329	123
NRG Energy, Inc. (Note Issuer)
Condensed Financial Statements, Captions [Line Items]
Net Income	(60)	200	387	(564)
Other Comprehensive Income/(Loss), net of tax
Unrealized gain/(loss) on derivatives, net	(13)	6	9	7
Foreign currency translation adjustments, net	(1)	4	(9)	10
Available-for-sale securities, net		1	1	2
Defined benefit plans, net	(1)	(1)	(3)	25
Other comprehensive income	(15)	10	(2)	44
Comprehensive (loss) income	(75)	210	385	(520)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	11	32	107	57
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	$ (86)	$ 178	$ 278	$ (577)

Condensed Consolidating Finan_6

Condensed Consolidating Financial Information - BALANCE SHEETS (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 1,359	$ 767	$ 1,022	$ 591
Funds deposited by counterparties	30	37	31	2
Restricted cash	28	279	$ 318	$ 267
Accounts receivable, net	1,297	960
Inventory	408	486
Derivative instruments	683	624
Deferred income tax	0
Cash collateral paid in support of energy risk management activities	209	171
Accounts receivable - affiliate	19	186
Prepayments and other current assets	248	179
Current assets - held for sale	0	116
Current assets - discontinued operations	4	705
Total current assets	4,285	4,510
Property, plant and equipment, net	3,599	6,435
Other Assets
Investment in subsidiaries	0	0
Equity investments in affiliates	452	182
Notes receivable, less current portion	10	2
Goodwill	539	539
Intangible assets, net	602	507
Nuclear decommissioning trust fund	719	692
Derivative instruments	392	159
Deferred income tax	11	6
Other non-current assets	281	294
Non-current assets held-for-sale	0	43
Non-current assets - discontinued operations	560	10,181
Total other assets	3,566	12,605
Total Assets	11,450	23,550
Current Liabilities
Current portion of long-term debt and capital leases	593	204
Accounts payable	824	711
Accounts payable - affiliate	14	57
Derivative instruments	550	537
Deferred Tax Liabilities, Net, Current	0
Cash collateral received in support of energy risk management activities	30	37
Accrued expenses and other current liabilities	659	769
Accrued expenses and other current liabilities-affiliate	1	161
Current liabilities - held-for-sale	0	72
Current liabilities - discontinued operations	52	864
Total current liabilities	2,723	3,412
Non-Current Liabilities
Long-term debt and capital leases	6,658	9,180
Nuclear decommissioning reserve	278	269
Nuclear decommissioning trust liability	432	415
Deferred income taxes	18	21
Derivative instruments	357	143
Out-of-market contracts, net	177	195
Other non-current liabilities	1,177	1,002
Non-current liabilities - held-for-sale	0	8
Non-current liabilities - discontinued operations	547	6,859
Total non-current liabilities	9,644	18,092
Total Liabilities	12,367	21,504
Redeemable noncontrolling interest in subsidiaries	19	78
Total Stockholders’ Equity	(936)	1,968
Total Liabilities and Stockholders’ Equity	11,450	23,550
Eliminations
Current Assets
Cash and cash equivalents	0	0
Funds deposited by counterparties	0	0
Restricted cash	0	0
Accounts receivable, net	0	0
Inventory	0	0
Derivative instruments	(45)	(57)
Deferred income tax	0
Cash collateral paid in support of energy risk management activities	0	0
Accounts receivable - affiliate	(1,256)	(534)
Prepayments and other current assets	0	0
Current assets - held for sale		0
Current assets - discontinued operations	0	0
Total current assets	(1,301)	(591)
Property, plant and equipment, net	0	(4)
Other Assets
Investment in subsidiaries	(4,856)	(7,847)
Equity investments in affiliates	0	0
Notes receivable, less current portion	(12)	0
Goodwill	0	0
Intangible assets, net	0	(3)
Nuclear decommissioning trust fund	0	0
Derivative instruments	(10)	0
Deferred income tax	0	0
Other non-current assets	0	0
Non-current assets held-for-sale		0
Non-current assets - discontinued operations	0	(22)
Total other assets	(4,878)	(7,872)
Total Assets	(6,179)	(8,467)
Current Liabilities
Current portion of long-term debt and capital leases	0	0
Accounts payable	0	0
Accounts payable - affiliate	(1,257)	(534)
Derivative instruments	(45)	(57)
Deferred Tax Liabilities, Net, Current	0
Cash collateral received in support of energy risk management activities	0	0
Accrued expenses and other current liabilities	0	0
Accrued expenses and other current liabilities-affiliate	0	0
Current liabilities - held-for-sale		0
Current liabilities - discontinued operations	0	0
Total current liabilities	(1,302)	(591)
Non-Current Liabilities
Long-term debt and capital leases	(12)	0
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Deferred income taxes	0	0
Derivative instruments	(10)	0
Out-of-market contracts, net	0	0
Other non-current liabilities	0	0
Non-current liabilities - held-for-sale		0
Non-current liabilities - discontinued operations	0	0
Total non-current liabilities	(22)	0
Total Liabilities	(1,324)	(591)
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders’ Equity	(4,855)	(7,876)
Total Liabilities and Stockholders’ Equity	(6,179)	(8,467)
Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	130	0
Funds deposited by counterparties	30	37
Restricted cash	5	4
Accounts receivable, net	1,151	911
Inventory	301	338
Derivative instruments	687	646
Deferred income tax	38
Cash collateral paid in support of energy risk management activities	194	170
Accounts receivable - affiliate	458	685
Prepayments and other current assets	160	122
Current assets - held for sale		8
Current assets - discontinued operations	0	0
Total current assets	3,154	2,921
Property, plant and equipment, net	2,372	2,507
Other Assets
Investment in subsidiaries	477	266
Equity investments in affiliates	0	0
Notes receivable, less current portion	0	0
Goodwill	359	360
Intangible assets, net	403	455
Nuclear decommissioning trust fund	719	692
Derivative instruments	357	126
Deferred income tax	34	377
Other non-current assets	92	50
Non-current assets held-for-sale		0
Non-current assets - discontinued operations	0	0
Total other assets	2,441	2,326
Total Assets	7,967	7,754
Current Liabilities
Current portion of long-term debt and capital leases	0	0
Accounts payable	705	609
Accounts payable - affiliate	1,610	742
Derivative instruments	565	556
Deferred Tax Liabilities, Net, Current	0
Cash collateral received in support of energy risk management activities	30	37
Accrued expenses and other current liabilities	282	304
Accrued expenses and other current liabilities-affiliate	0	0
Current liabilities - held-for-sale		0
Current liabilities - discontinued operations	0	0
Total current liabilities	3,192	2,248
Non-Current Liabilities
Long-term debt and capital leases	244	244
Nuclear decommissioning reserve	278	269
Nuclear decommissioning trust liability	432	415
Deferred income taxes	112	112
Derivative instruments	361	136
Out-of-market contracts, net	54	66
Other non-current liabilities	410	410
Non-current liabilities - held-for-sale		0
Non-current liabilities - discontinued operations	0	0
Total non-current liabilities	1,891	1,652
Total Liabilities	5,083	3,900
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders’ Equity	2,884	3,854
Total Liabilities and Stockholders’ Equity	7,967	7,754
Non-Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	22	124
Funds deposited by counterparties	0	0
Restricted cash	15	275
Accounts receivable, net	97	45
Inventory	107	148
Derivative instruments	24	26
Deferred income tax	80
Cash collateral paid in support of energy risk management activities	15	1
Accounts receivable - affiliate	55	183
Prepayments and other current assets	35	30
Current assets - held for sale		108
Current assets - discontinued operations	4	705
Total current assets	454	1,645
Property, plant and equipment, net	1,077	3,695
Other Assets
Investment in subsidiaries	0	0
Equity investments in affiliates	452	180
Notes receivable, less current portion	10	2
Goodwill	180	179
Intangible assets, net	199	55
Nuclear decommissioning trust fund	0	0
Derivative instruments	9	2
Deferred income tax	(149)	(135)
Other non-current assets	70	124
Non-current assets held-for-sale		43
Non-current assets - discontinued operations	560	10,203
Total other assets	1,331	10,653
Total Assets	2,862	15,993
Current Liabilities
Current portion of long-term debt and capital leases	89	183
Accounts payable	55	47
Accounts payable - affiliate	(191)	(332)
Derivative instruments	30	38
Deferred Tax Liabilities, Net, Current	1
Cash collateral received in support of energy risk management activities	0	0
Accrued expenses and other current liabilities	40	64
Accrued expenses and other current liabilities-affiliate	0	0
Current liabilities - held-for-sale		72
Current liabilities - discontinued operations	52	859
Total current liabilities	76	931
Non-Current Liabilities
Long-term debt and capital leases	244	2,197
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Deferred income taxes	62	64
Derivative instruments	6	7
Out-of-market contracts, net	123	129
Other non-current liabilities	197	201
Non-current liabilities - held-for-sale		8
Non-current liabilities - discontinued operations	547	6,859
Total non-current liabilities	1,179	9,465
Total Liabilities	1,255	10,396
Redeemable noncontrolling interest in subsidiaries	19	78
Total Stockholders’ Equity	1,588	5,519
Total Liabilities and Stockholders’ Equity	2,862	15,993
NRG Energy, Inc. (Note Issuer)
Current Assets
Cash and cash equivalents	1,207	643
Funds deposited by counterparties	0	0
Restricted cash	8	0
Accounts receivable, net	49	4
Inventory	0	0
Derivative instruments	17	9
Deferred income tax	(118)
Cash collateral paid in support of energy risk management activities	0	0
Accounts receivable - affiliate	762	(148)
Prepayments and other current assets	53	27
Current assets - held for sale		0
Current assets - discontinued operations	0	0
Total current assets	1,978	535
Property, plant and equipment, net	150	237
Other Assets
Investment in subsidiaries	4,379	7,581
Equity investments in affiliates	0	2
Notes receivable, less current portion	12	0
Goodwill	0	0
Intangible assets, net	0	0
Nuclear decommissioning trust fund	0	0
Derivative instruments	36	31
Deferred income tax	126	(236)
Other non-current assets	119	120
Non-current assets held-for-sale		0
Non-current assets - discontinued operations	0	0
Total other assets	4,672	7,498
Total Assets	6,800	8,270
Current Liabilities
Current portion of long-term debt and capital leases	504	21
Accounts payable	64	55
Accounts payable - affiliate	(148)	181
Derivative instruments	0	0
Deferred Tax Liabilities, Net, Current	(1)
Cash collateral received in support of energy risk management activities	0	0
Accrued expenses and other current liabilities	337	401
Accrued expenses and other current liabilities-affiliate	1	161
Current liabilities - held-for-sale		0
Current liabilities - discontinued operations	0	5
Total current liabilities	757	824
Non-Current Liabilities
Long-term debt and capital leases	6,182	6,739
Nuclear decommissioning reserve	0	0
Nuclear decommissioning trust liability	0	0
Deferred income taxes	(156)	(155)
Derivative instruments	0	0
Out-of-market contracts, net	0	0
Other non-current liabilities	570	391
Non-current liabilities - held-for-sale		0
Non-current liabilities - discontinued operations	0	0
Total non-current liabilities	6,596	6,975
Total Liabilities	7,353	7,799
Redeemable noncontrolling interest in subsidiaries	0	0
Total Stockholders’ Equity	(553)	471
Total Liabilities and Stockholders’ Equity	$ 6,800	$ 8,270

Condensed Consolidating Finan_7

Condensed Consolidating Financial Information - CASH FLOWS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities
Net (Loss)/Income	$ (48)	$ 163	$ 281	$ (682)
Loss from discontinued operations	(354)	(22)	(320)	(798)
Net income	306	185	601	116
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions and equity in earnings of unconsolidated affiliates			10	0
Depreciation, amortization and accretion			403	490
Provision for bad debts			57	57
Amortization of nuclear fuel			38	37
Amortization of financing costs and debt discount/premiums			21	15
Adjustment for debt extinguishment			22	3
Amortization of intangibles and out-of-market contracts			21	79
Amortization of unearned equity compensation			36	27
Impairment losses			89	60
Changes in deferred income taxes and liability for uncertain tax benefits			(6)	(1)
Changes in nuclear decommissioning trust liability			50	20
Changes in derivative instruments			(17)	36
Changes in collateral deposits in support of energy risk management activities			(30)	(103)
Gain on sale of emission allowances			(20)	21
Gain on sale of assets	(14)		(30)	(4)
GenOn settlement in July 2018			(125)	0
Loss on deconsolidation of business			13	0
Changes in other working capital			(375)	(295)
Cash provided/(used) by continuing operations			758	558
Cash provided by discontinued operations			324	178
Net Cash Provided/(Used) by Operating Activities			1,082	736
Cash Flows from Investing Activities
Intercompany dividends				0
Acquisitions of businesses, net of cash acquired			(209)	(12)
Capital expenditures			(345)	(172)
Purchases of emission allowances			(30)	(47)
Proceeds from sale of emission allowances			54	104
Investments in nuclear decommissioning trust fund securities			(449)	(402)
Proceeds from the sale of nuclear decommissioning trust fund securities			398	382
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees			1,555	309
Deconsolidation of business			(268)	0
Change in investments in unconsolidated affiliates			(62)	24
Other			0	30
Cash (used)/provided by continuing operations			644	216
Cash used by discontinued operations			(703)	(638)
Net Cash (Used)/Provided by Investing Activities			(59)	(422)
Cash Flows from Financing Activities
Payments (for)/from intercompany loans			0	0
Intercompany dividends				0
Payment of dividends to common stockholders			(28)	(28)
Payment for treasury stock			(1,000)	0
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			995	308
Payments for short and long-term debt			(970)	(343)
Increase in notes receivable from affiliate			(26)	(125)
Net distributions to noncontrolling interests in subsidiaries			(17)	(18)
Payment of debt issuance costs			(19)	(39)
Other			(4)	(8)
Cash provided/(used) by continuing operations			(1,069)	(253)
Cash provided by discontinued operations			403	39
Net Cash Provided/(Used) by Financing Activities			(666)	(214)
Effect of exchange rate changes on cash and cash equivalents			1	(10)
Change in Cash from discontinued operations			24	(421)
Net Increase in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			334	511
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			1,083	860
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	1,417	1,371	1,417	1,371
Eliminations
Cash Flows from Operating Activities
Net (Loss)/Income	(399)	(500)	(1,095)	(827)
Loss from discontinued operations	0	0	0	0
Net income	(399)	(500)	(1,095)	(827)
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions and equity in earnings of unconsolidated affiliates			0	62
Depreciation, amortization and accretion			0	0
Provision for bad debts			0	0
Amortization of nuclear fuel			0	0
Amortization of financing costs and debt discount/premiums			0	0
Adjustment for debt extinguishment			0	0
Amortization of intangibles and out-of-market contracts			0	0
Amortization of unearned equity compensation			0	0
Impairment losses			0	0
Changes in deferred income taxes and liability for uncertain tax benefits			0	0
Changes in nuclear decommissioning trust liability			0	0
Changes in derivative instruments			(15)	(8)
Changes in collateral deposits in support of energy risk management activities			0	0
Gain on sale of emission allowances			0	0
Gain on sale of assets			0	0
GenOn settlement in July 2018			0
Loss on deconsolidation of business			0
Changes in other working capital			1,110	773
Cash provided/(used) by continuing operations			0	0
Cash provided by discontinued operations			0	0
Net Cash Provided/(Used) by Operating Activities			0	0
Cash Flows from Investing Activities
Intercompany dividends				(129)
Acquisitions of businesses, net of cash acquired			0	0
Capital expenditures			0	0
Purchases of emission allowances			0	0
Proceeds from sale of emission allowances			0	0
Investments in nuclear decommissioning trust fund securities			0	0
Proceeds from the sale of nuclear decommissioning trust fund securities			0	0
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees			0	0
Deconsolidation of business			0
Change in investments in unconsolidated affiliates			0	0
Other				0
Cash (used)/provided by continuing operations			0	(129)
Cash used by discontinued operations				0
Net Cash (Used)/Provided by Investing Activities			0	(129)
Cash Flows from Financing Activities
Payments (for)/from intercompany loans			0	0
Intercompany dividends				129
Payment of dividends to common stockholders			0	0
Payment for treasury stock			0
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			0	0
Payments for short and long-term debt			0	0
Increase in notes receivable from affiliate				0
Net distributions to noncontrolling interests in subsidiaries			0	0
Payment of debt issuance costs			0	0
Other			0	0
Cash provided/(used) by continuing operations			0	129
Cash provided by discontinued operations			0	0
Net Cash Provided/(Used) by Financing Activities			0	129
Effect of exchange rate changes on cash and cash equivalents			0	0
Change in Cash from discontinued operations			0	0
Net Increase in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			0	0
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			0	0
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	0	0	0	0
Guarantor Subsidiaries
Cash Flows from Operating Activities
Net (Loss)/Income	306	342	849	737
Loss from discontinued operations	0	0	0	0
Net income	306	342	849	737
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions and equity in earnings of unconsolidated affiliates			0	0
Depreciation, amortization and accretion			240	299
Provision for bad debts			55	42
Amortization of nuclear fuel			38	37
Amortization of financing costs and debt discount/premiums			0	0
Adjustment for debt extinguishment			0	0
Amortization of intangibles and out-of-market contracts			15	20
Amortization of unearned equity compensation			0	0
Impairment losses			0	42
Changes in deferred income taxes and liability for uncertain tax benefits			343	0
Changes in nuclear decommissioning trust liability			50	20
Changes in derivative instruments			(38)	(11)
Changes in collateral deposits in support of energy risk management activities			(16)	(126)
Gain on sale of emission allowances			(20)	21
Gain on sale of assets			(3)	(4)
GenOn settlement in July 2018			0
Loss on deconsolidation of business			0
Changes in other working capital			(567)	(1,035)
Cash provided/(used) by continuing operations			946	42
Cash provided by discontinued operations			0	0
Net Cash Provided/(Used) by Operating Activities			946	42
Cash Flows from Investing Activities
Intercompany dividends				0
Acquisitions of businesses, net of cash acquired			(2)	0
Capital expenditures			(158)	(135)
Purchases of emission allowances			(30)	(47)
Proceeds from sale of emission allowances			54	105
Investments in nuclear decommissioning trust fund securities			(449)	(402)
Proceeds from the sale of nuclear decommissioning trust fund securities			398	382
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees			10	36
Deconsolidation of business			0
Change in investments in unconsolidated affiliates			0	0
Other				30
Cash (used)/provided by continuing operations			(177)	(31)
Cash used by discontinued operations			0	0
Net Cash (Used)/Provided by Investing Activities			(177)	(31)
Cash Flows from Financing Activities
Payments (for)/from intercompany loans			(645)	9
Intercompany dividends				0
Payment of dividends to common stockholders			0	0
Payment for treasury stock			0
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			0	0
Payments for short and long-term debt			0	0
Increase in notes receivable from affiliate			0	0
Net distributions to noncontrolling interests in subsidiaries			0	0
Payment of debt issuance costs			0	0
Other			0	0
Cash provided/(used) by continuing operations			(645)	9
Cash provided by discontinued operations			0	0
Net Cash Provided/(Used) by Financing Activities			(645)	9
Effect of exchange rate changes on cash and cash equivalents			0	0
Change in Cash from discontinued operations			0	0
Net Increase in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			124	20
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			41	3
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	165	23	165	23
Non-Guarantor Subsidiaries
Cash Flows from Operating Activities
Net (Loss)/Income	105	121	140	(28)
Loss from discontinued operations	17	12	77	(134)
Net income	88	109	63	106
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions and equity in earnings of unconsolidated affiliates			9	(65)
Depreciation, amortization and accretion			138	167
Provision for bad debts			2	0
Amortization of nuclear fuel			0	0
Amortization of financing costs and debt discount/premiums			5	2
Adjustment for debt extinguishment			0	3
Amortization of intangibles and out-of-market contracts			6	59
Amortization of unearned equity compensation			0	0
Impairment losses			89	18
Changes in deferred income taxes and liability for uncertain tax benefits			11	(7)
Changes in nuclear decommissioning trust liability			0	0
Changes in derivative instruments			40	43
Changes in collateral deposits in support of energy risk management activities			(14)	23
Gain on sale of emission allowances			0	0
Gain on sale of assets			(27)	0
GenOn settlement in July 2018			0
Loss on deconsolidation of business			13
Changes in other working capital			(61)	(484)
Cash provided/(used) by continuing operations			274	(135)
Cash provided by discontinued operations			324	178
Net Cash Provided/(Used) by Operating Activities			598	43
Cash Flows from Investing Activities
Intercompany dividends				0
Acquisitions of businesses, net of cash acquired			(207)	(12)
Capital expenditures			(150)	(18)
Purchases of emission allowances			0	0
Proceeds from sale of emission allowances			0	(1)
Investments in nuclear decommissioning trust fund securities			0	0
Proceeds from the sale of nuclear decommissioning trust fund securities			0	0
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees			8	0
Deconsolidation of business			(268)
Change in investments in unconsolidated affiliates			(62)	24
Other				0
Cash (used)/provided by continuing operations			(679)	(7)
Cash used by discontinued operations			(703)	(638)
Net Cash (Used)/Provided by Investing Activities			(1,382)	(645)
Cash Flows from Financing Activities
Payments (for)/from intercompany loans			(12)	417
Intercompany dividends				(129)
Payment of dividends to common stockholders			0	0
Payment for treasury stock			0
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			163	94
Payments for short and long-term debt			(106)	(124)
Increase in notes receivable from affiliate			0	(125)
Net distributions to noncontrolling interests in subsidiaries			(17)	(18)
Payment of debt issuance costs			0	(34)
Other			(4)	(8)
Cash provided/(used) by continuing operations			24	73
Cash provided by discontinued operations			403	39
Net Cash Provided/(Used) by Financing Activities			427	112
Effect of exchange rate changes on cash and cash equivalents			1	(10)
Change in Cash from discontinued operations			24	(421)
Net Increase in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			(380)	(79)
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			399	534
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	19	455	19	455
NRG Energy, Inc. (Note Issuer)
Cash Flows from Operating Activities
Net (Loss)/Income	(60)	200	387	(564)
Loss from discontinued operations	(371)	(34)	(397)	(664)
Net income	311	234	784	100
Adjustments to reconcile net income to net cash provided/(used) by operating activities:
Distributions and equity in earnings of unconsolidated affiliates			1	3
Depreciation, amortization and accretion			25	24
Provision for bad debts			0	15
Amortization of nuclear fuel			0	0
Amortization of financing costs and debt discount/premiums			16	13
Adjustment for debt extinguishment			22	0
Amortization of intangibles and out-of-market contracts			0	0
Amortization of unearned equity compensation			36	27
Impairment losses			0	0
Changes in deferred income taxes and liability for uncertain tax benefits			(360)	6
Changes in nuclear decommissioning trust liability			0	0
Changes in derivative instruments			(4)	12
Changes in collateral deposits in support of energy risk management activities			0	0
Gain on sale of emission allowances			0	0
Gain on sale of assets			0	0
GenOn settlement in July 2018			(125)
Loss on deconsolidation of business			0
Changes in other working capital			(857)	451
Cash provided/(used) by continuing operations			(462)	651
Cash provided by discontinued operations			0	0
Net Cash Provided/(Used) by Operating Activities			(462)	651
Cash Flows from Investing Activities
Intercompany dividends				129
Acquisitions of businesses, net of cash acquired			0	0
Capital expenditures			(37)	(19)
Purchases of emission allowances			0	0
Proceeds from sale of emission allowances			0	0
Investments in nuclear decommissioning trust fund securities			0	0
Proceeds from the sale of nuclear decommissioning trust fund securities			0	0
Proceeds from sale of assets, net of cash disposed and sale of discontinued operations, net of fees			1,537	273
Deconsolidation of business			0
Change in investments in unconsolidated affiliates			0	0
Other				0
Cash (used)/provided by continuing operations			1,500	383
Cash used by discontinued operations				0
Net Cash (Used)/Provided by Investing Activities			1,500	383
Cash Flows from Financing Activities
Payments (for)/from intercompany loans			657	(426)
Intercompany dividends				0
Payment of dividends to common stockholders			(28)	(28)
Payment for treasury stock			(1,000)
Net receipts from settlement of acquired derivatives that include financing elements				0
Proceeds from issuance of long-term debt			832	214
Payments for short and long-term debt			(864)	(219)
Increase in notes receivable from affiliate			(26)	0
Net distributions to noncontrolling interests in subsidiaries			0	0
Payment of debt issuance costs			(19)	(5)
Other			0	0
Cash provided/(used) by continuing operations			(448)	(464)
Cash provided by discontinued operations			0	0
Net Cash Provided/(Used) by Financing Activities			(448)	(464)
Effect of exchange rate changes on cash and cash equivalents			0	0
Change in Cash from discontinued operations			0	0
Net Increase in Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash			590	570
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at Beginning of Period			643	323
Cash and Cash Equivalents, Funds Deposited by Counterparties and Restricted Cash at End of Period	$ 1,233	$ 893	$ 1,233	$ 893