NRG Energy (NRG) 10-Q 12 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 31, 2013
Document And Entity Information [Abstract]	'	'
Entity Registrant Name	'NRG ENERGY, INC.	'
Entity Central Index Key	'0001013871	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-13	'
Amendment Flag	'false	'
Current Fiscal Year End Date	'--12-31	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	323,416,260
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating Revenues	'	'	'	'
Total operating revenues	$3,490	$2,331	$8,500	$6,359
Operating Costs and Expenses	'	'	'	'
Cost of operations	2,355	1,740	6,179	4,660
Depreciation and amortization	318	239	921	703
Selling, general and administrative	229	224	671	613
Acquisition-related transaction and integration costs	26	18	95	18
Development activity expenses	27	24	63	52
Total operating costs and expenses	2,955	2,245	7,929	6,046
Operating Income	535	86	571	313
Other Income/(Expense)	'	'	'	'
Equity in (losses)/earnings of unconsolidated affiliates	-5	4	6	26
Other income, net	5	9	9	12
Loss on debt extinguishment	-1	-41	-50	-41
Interest expense	-228	-163	-630	-495
Total other expense	-229	-191	-665	-498
Income/(Loss) Before Income Taxes	306	-105	-94	-185
Income tax expense/(benefit)	163	-113	-47	-246
Net Income/(Loss)	143	8	-47	61
Less: Net income attributable to noncontrolling interest	19	9	27	18
Net Income/(Loss) Attributable to NRG Energy, Inc.	124	-1	-74	43
Dividends for preferred shares	2	2	7	7
Income/(Loss) Available for Common Stockholders	$122	($3)	($81)	$36
Earnings/(Loss) Per Share Attributable to NRG Energy, Inc. Common Stockholders	'	'	'	'
Weighted average number of common shares outstanding	323	228	323	228
Earnings/(Loss) per Weighted Average Common Share — Basic	$0.38	($0.01)	($0.25)	$0.16
Weighted average number of shares outstanding, diluted	327	228	323	230
Net loss per weighted average common share — diluted	$0.37	($0.01)	($0.25)	$0.16
Dividends Per Common Share	$0.12	$0.09	$0.33	$0.09

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Loss (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2013	Sep. 30, 2012
Net Income/(Loss)	$143	$8	'	($47)	$61
Other Comprehensive (Loss)/Income, net of tax	'	'	'	'	'
Unrealized (loss)/gain on derivatives, net of income tax benefit of $5, $24, $2 and $76	-16	-43	'	8	-132
Foreign currency translation adjustments, net of income tax benefit of $1, $0, $13 and $1	5	1	'	-14	-1
Reclassification adjustment for translation gain realized upon sale of Schkopau, net of income tax expense of $0, $6, $0 and $6	0	-11	'	0	-11
Available-for-sale securities, net of income tax expense of $0, $1, $1 and $1	0	2	2	2	2
Defined benefit plans, net of tax expense of $0, $0, $4 and $0	0	0	'	25	0
Other comprehensive (loss)/income	-11	-51	'	21	-142
Comprehensive Income/(Loss)	132	-43	'	-26	-81
Less: Comprehensive income attributable to noncontrolling interest	-18	-9	'	-26	-18
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	114	-52	'	-52	-99
Dividends for preferred shares	2	2	'	7	7
Comprehensive Income/(Loss) Available for Common Stockholders	$112	($54)	'	($59)	($106)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statement of Comprehensive Loss Income (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Unrealized gain/loss on derivatives, income tax benefit	$5	$24	$2	$76
Foreign currency translation adjustments, income tax benefit	1	0	13	1
Reclassification adjustment for translation gain realized upon sale of Schkopau, income tax expense	0	6	0	6
Available-for-sale securities, income tax expense	0	1	1	1
Defined benefit plans, income tax expense	$0	$0	$4	$0

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Current Assets	'	'
Cash and cash equivalents	$2,129	$2,087
Funds deposited by counterparties	122	271
Restricted cash	307	217
Accounts receivable — trade, less allowance for doubtful accounts of $41 and $32	1,366	1,061
Inventory	861	911
Derivative instruments	1,389	2,644
Cash collateral paid in support of energy risk management activities	288	229
Deferred income taxes	0	56
Renewable energy grant receivable	345	58
Prepayments and other current assets	442	401
Total current assets	7,249	7,935
Property, plant and equipment, net of accumulated depreciation of $6,264 and $5,417	20,600	20,241
Other Assets	'	'
Equity investments in affiliates	626	676
Notes receivable, less current portion	76	79
Goodwill	1,953	1,956
Intangible assets, net of accumulated amortization of $1,915 and $1,706	1,141	1,200
Nuclear decommissioning trust fund	524	473
Derivative instruments	506	662
Deferred income taxes	1,499	1,282
Other non-current assets	689	600
Total other assets	7,014	6,928
Total Assets	34,863	35,104
Current Liabilities	'	'
Current portion of long-term debt and capital leases	911	147
Accounts payable	1,140	1,171
Derivative instruments	1,064	1,981
Deferred income taxes	112	0
Cash collateral received in support of energy risk management activities	122	271
Accrued expenses and other current liabilities	1,033	1,085
Total current liabilities	4,382	4,655
Other Liabilities	'	'
Long-term debt and capital leases	15,802	15,736
Nuclear decommissioning reserve	290	354
Nuclear decommissioning trust liability	303	273
Deferred income taxes	50	55
Derivative instruments	372	500
Out-of-market contracts	1,157	1,231
Other non-current liabilities	1,377	1,553
Total non-current liabilities	19,351	19,702
Total Liabilities	23,733	24,357
3.625% convertible perpetual preferred stock (at liquidation value, net of issuance costs)	249	249
Commitments and Contingencies	'	'
Stockholders’ Equity	'	'
Common stock	4	4
Additional paid-in capital	7,843	7,587
Retained earnings	4,272	4,459
Less treasury stock, at cost — 77,347,528 and 76,505,718 shares, respectively	-1,942	-1,920
Accumulated other comprehensive loss	-129	-150
Noncontrolling interest	833	518
Total Stockholders’ Equity	10,881	10,498
Total Liabilities and Stockholders’ Equity	$34,863	$35,104

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, except Share data, unless otherwise specified
Accounts receivable - trade, allowance for doubtful accounts	$41	$32
Property, plant and equipment, accumulated depreciation	6,264	5,417
Intangible assets, accumulated amortization	$1,915	$1,706
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	3.63%	3.63%
Treasury stock, shares (in shares)	77,347,528	76,505,718

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities	'	'
Net Income/(Loss)	($47)	$61
Adjustments to reconcile net (loss)/income to net cash provided by operating activities:	'	'
Distributions and equity in earnings of unconsolidated affiliates	23	8
Depreciation and amortization	921	703
Provision for bad debts	49	40
Amortization of nuclear fuel	27	29
Amortization of financing costs and debt discount/premiums	-22	25
Adjustment to loss on debt extinguishment	-15	8
Amortization of intangibles and out-of-market contracts	75	108
Amortization of unearned equity compensation	32	27
Changes in deferred income taxes and liability for uncertain tax benefits	39	-261
Changes in nuclear decommissioning trust liability	25	25
Changes in derivative instruments	189	360
Changes in collateral deposits supporting energy risk management activities	-59	213
Gain on sale of emission allowances	-8	-3
Cash used by changes in other working capital	-406	-285
Net Cash Provided by Operating Activities	823	1,058
Cash Flows from Investing Activities	'	'
Acquisitions of businesses, net of cash acquired	-374	-40
Capital expenditures	-1,581	-2,474
Increase in restricted cash, net	-67	-96
(Increase)/decrease in restricted cash to support equity requirements for U.S. DOE funded projects	-20	151
Increase in notes receivable	-22	-22
Investments in nuclear decommissioning trust fund securities	-369	-341
Proceeds from sales of nuclear decommissioning trust fund securities	344	316
Proceeds from renewable energy grants	52	49
Proceeds from sale of assets, net of cash disposed of	-13	-137
Other	-7	-9
Net Cash Used by Investing Activities	-2,031	-2,329
Cash Flows from Financing Activities	'	'
Payment of dividends to common and preferred stockholders	-113	-28
Payment for treasury stock	-25	0
Net receipts from/(payments for) settlement of acquired derivatives that include financing elements	177	-65
Proceeds from issuance of long-term debt	1,605	2,541
Sale proceeds and other contributions from noncontrolling interest in subsidiaries	504	316
Proceeds from issuance of common stock	14	0
Payment of debt issuance costs	-43	-30
Payments for short and long-term debt	-868	-955
Net Cash Provided by Financing Activities	1,251	1,779
Effect of exchange rate changes on cash and cash equivalents	-1	-3
Net Increase in Cash and Cash Equivalents	42	505
Cash and Cash Equivalents at Beginning of Period	2,087	1,105
Cash and Cash Equivalents at End of Period	$2,129	$1,610

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2013
Basis of Presentation Disclosure [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	NRG Energy, Inc., or NRG or the Company, is historically a competitive power and energy company that aspires to be a leader in the way residential, industrial and commercial consumers think about, use, produce and deliver energy and energy services in major competitive power markets in the United States. NRG engages in the ownership and operation of power generation facilities; the trading of energy, capacity and related products; the transacting in and trading of fuel and transportation services and the direct sale of energy, services, and innovative, sustainable products to retail customers in competitive markets in which NRG owns generation. The Company sells retail electric products and services under the name “NRG” and various brands owned by NRG. Finally, NRG is a clean energy leader and is focused on the deployment and commercialization of potentially transformative technologies, like electric vehicles, Distributed Solar and smart meter/home automation technology that collectively have the potential to fundamentally change the nature of the power industry, including a substantial change in the role of the national electric transmission grid and distribution system. On December 14, 2012, the Company acquired GenOn as further described in Note 3, Business Acquisitions and Dispositions, and has reported results of operations from the acquisition date forward.
	The Company formed NRG Yield, Inc. to own and operate a portfolio of contracted generation assets and thermal infrastructure assets that have historically been owned and/or operated by NRG and its subsidiaries. On July 22, 2013, NRG Yield, Inc. closed its initial public offering of 22,511,250 shares of Class A common stock at a price of $22 per share. Net proceeds to NRG Yield, Inc. from the sale of the Class A common stock were approximately $468 million, net of underwriting discounts and commissions of $27 million. The Company retained 42,738,250 shares of Class B common stock of NRG Yield, Inc. As a result, the Company owns a controlling interest in NRG Yield, Inc. and will consolidate this entity for financial reporting purposes. In addition, the Company retained a 65.5% interest in NRG Yield LLC. The initial public offering represented the sale of a 34.5% interest in NRG Yield LLC. NRG Yield LLC's initial assets consist of three natural gas or dual-fired facilities, eight utility-scale solar and wind generation facilities, two portfolios of distributed solar facilities that collectively represent 1,324 net MW, and thermal infrastructure assets with an aggregate steam and chilled water capacity of 1,098 net MWt and electric generation capacity of 123 net MW. The following table represents the structure of NRG Yield, Inc. after the initial public offering:
	The Company has revised its segment reporting to include an NRG Yield segment, as further described in Note 11, Segment Reporting.
	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 financial statements in the Company's 2012 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, 2013, and the results of operations, comprehensive income/(loss) and cash flows for the three and nine months ended September 30, 2013, and 2012.
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States 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 or cash flows. The Company reclassified certain plant-related expenses from selling, general and administrative to cost of operations and certain general and administrative expenses to development activity expenses.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
Significant Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	Summary of Significant Accounting Policies
	Development Activity Expenses
	Development activity expenses include project development costs, which are expensed in the preliminary stages of a project and capitalized when the project is deemed to be commercially viable. Commercial viability is determined by one or a series of actions including, among others, Board of Director approval pursuant to a formal project plan that subjects the Company to significant future obligations that can only be discharged by the use of a Company asset. When a project is available for operations, capitalized project development costs are reclassified to property, plant and equipment and amortized on a straight-line basis over the estimated useful life of the project's related assets. Capitalized costs are charged to expense if a project is abandoned or management otherwise determines the costs to be unrecoverable.
	Development activity expenses also include selling, general, and administrative expenses associated with the current operations of certain developing businesses including residential solar, electric vehicles, waste-to-energy, carbon capture and other emerging technologies. The revenue associated with these businesses was immaterial for the three and nine months ended September 30, 2013 and 2012. When it is determined that a business will remain an ongoing part of the Company's operations or when operating revenues become material relative to the operating costs of the underlying business, the Company no longer classifies a business as a development activity.
	Other Cash Flow Information
	NRG’s investing activities exclude capital expenditures of $127 million which were accrued and unpaid at September 30, 2013, primarily for solar projects under construction.
	Noncontrolling Interest
	The following table reflects the changes in NRG's noncontrolling interest balance:
		(In millions)
	Balance as of December 31, 2012	$	518
	Contributions from noncontrolling interest	289
	Comprehensive income attributable to noncontrolling interest	26
	Balance as of September 30, 2013	$	833
	The contributions from noncontrolling interest primarily reflect the value of the underlying net assets sold to the NRG Yield, Inc. Class A common shareholders in the initial public offering. The transaction resulted in a gain of $221 million, which was recorded in NRG's additional paid-in capital balance.
	Recent Accounting Developments
	ASU 2011-11 - Effective January 1, 2013, the Company adopted the provisions of ASU No. 2011-11, Balance Sheet (Topic 210) Disclosures about Offsetting Assets and Liabilities, or ASU No. 2011-11, and began providing enhanced disclosures regarding the effect or potential effect of netting arrangements on an entity's financial position by improving information about financial instruments and derivative instruments that either (1) offset in accordance with either ASC 210-20-45 or ASC 810-20-45 or (2) are subject to an enforceable master netting arrangement or similar agreement, irrespective of whether they are offset. Reporting entities are required to disclose both gross and net information about both instruments and transactions eligible for offset in the statement of financial position and instruments and transactions subject to an agreement similar to a master netting arrangement. The disclosures required by ASU No. 2011-11 are required to be adopted retroactively. As this guidance provides only disclosure requirements, the adoption of this standard did not impact the Company's results of operations, cash flows or financial position.
	ASU 2013-02 - Effective January 1, 2013, the Company adopted the provisions of ASU No. 2013-02, Other Comprehensive Income (Topic 220) Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, or ASU No. 2013-02, and began reporting the effect of significant reclassifications out of accumulated other comprehensive income on the respective line items in net income within the notes to the financial statements if the amount being reclassified is required under U.S. GAAP to be reclassified in its entirety to net income in the same reporting period. For other amounts not required by U.S. GAAP to be reclassified in their entirety to net income in the same reporting period, an entity is required to cross-reference other disclosures which provide additional information about the amounts.  The provisions of ASU No. 2013-02 are required to be adopted prospectively.  As this guidance provides only presentation requirements, the adoption of this standard did not impact the Company's results of operations, cash flows or financial position.

Business_Acquisitions_and_Disp

Business Acquisitions and Dispositions	9 Months Ended
	Sep. 30, 2013
Business Acquisitions and Dispositions [Abstract]	'
Business Acquisitions and Dispositions	'
	Business Acquisitions and Dispositions
	Pending Acquisition
	On October 18, 2013, the Company entered into an agreement to acquire substantially all of the assets of Edison Mission Energy, or EME.  EME, through its subsidiaries and affiliates, owns, operates, and leases a portfolio of 8,000 MW consisting of wind energy facilities and coal- and gas-fired generating facilities. On December 17, 2012, EME and certain of its direct and indirect subsidiaries filed voluntary petitions for relief under chapter 11 of title 11 of the United States Code, or the Bankruptcy Code.  EME was deconsolidated from its parent company, Edison International, for financial statement purposes but not for tax purposes on December 17, 2012.  On May 2, 2013, certain other subsidiaries of EME filed voluntary petitions for relief under the Bankruptcy Code.
	The Company will pay an aggregate purchase price of $2.6 billion (subject to adjustment), which will consist of 12,671,977 shares of NRG common stock (valued at $350 million based upon the volume-weighted average trading price over the 20 trading days prior to October 18, 2013) with the balance to be paid in cash. The Company expects to fund the net cash portion of the purchase price using a combination of cash on hand, including acquired cash on hand of $1.1 billion, and approximately $700 million in newly-issued corporate debt. The Company also expects to assume non-recourse debt of approximately $1.5 billion.
	In connection with the transaction, NRG has agreed to certain conditions with the parties to the Powerton and Joliet, or POJO, sale-leaseback transaction subject to which an NRG subsidiary will assume the POJO leveraged leases and NRG will guarantee the remaining payments under each lease. In connection with this agreement, NRG has committed to fund up to $350 million in capital expenditures for plant modifications at Powerton and Joliet to install controls to comply with MATS.
	The acquisition is subject to customary conditions, including approval of the U.S. Bankruptcy Court for the Northern District of Illinois and required regulatory approvals, and is expected to close by the first quarter of 2014.  However, EME may continue to solicit alternative transaction proposals from third parties through December 6, 2013.  Under certain circumstances, including if EME enters into or seeks approval of an alternative transaction, NRG will receive a cash fee of $65 million plus expense reimbursement.  There are no assurances that the conditions to the acquisition of EME will be satisfied, that EME will not seek or enter into an alternative transaction, or that the acquisition of EME will be consummated on the terms agreed to, if at all.
	Gregory Acquisition
	On August 7, 2013, NRG Texas Gregory, LLC, a wholly owned subsidiary of NRG, acquired Gregory Power Partners, L.P. for approximately $245 million in cash, net of $32 million cash acquired. Gregory is a cogeneration plant located in Corpus Christi, Texas, which has generation capacity of 388 MW and steam capacity of 160 MWt. The Gregory cogeneration plant provides steam, processed water and a small percentage of its electrical generation to the Corpus Christi Sherwin Alumina plant. The majority of the plant's generation is available for sale in the ERCOT market. The acquisition was recorded as a business combination under ASC 805, with identifiable assets acquired and liabilities assumed provisionally recorded at their estimated fair values on the acquisition date. The purchase price was provisionally allocated primarily to property, plant, and equipment. The initial accounting for the business combination is not complete because the evaluations necessary to assess the fair value of certain net assets acquired are still in process.
	GenOn Acquisition
	On December 14, 2012, NRG acquired GenOn Energy, Inc., or GenOn.  GenOn, a generator of wholesale electricity, has baseload, intermediate and peaking power generation facilities using coal, natural gas and oil, totaling approximately 21,440 MW.  Consideration for the acquisition was valued at $2.2 billion and was comprised of 0.1216 shares of NRG common stock for each outstanding share of GenOn, including restricted stock units outstanding, on the acquisition date, except for fractional shares which were paid in cash.  The Company issued 93.9 million shares of NRG common stock, or 29% of total common shares outstanding following the closing of the transaction. The acquisition was recorded as a business combination, with identifiable assets acquired and liabilities assumed provisionally recorded at their estimated fair values on the acquisition date. The initial accounting for the business combination is not complete because the evaluations necessary to assess the fair value of certain net assets acquired are still in process. See Note 3, Business Acquisitions and Dispositions, in the Company's 2012 Form 10-K for additional information related to the GenOn acquisition.
	The following table summarizes the provisional amounts recognized for assets acquired and liabilities assumed as of the acquisition date as well as adjustments made during the nine months ended September 30, 2013 to the amounts initially recorded in 2012 due to the ongoing evaluation of initial estimates. The measurement period adjustments were recorded as an adjustment to the gain on bargain purchase and did not have a significant impact on the Company's consolidated statements of operations, cash flows or financial position in any period. The allocation of the purchase price may be modified up to one year from the date of the acquisition as more information is obtained about the fair value of assets acquired and liabilities assumed.
	(In millions)	Amounts Recognized		Measurement Period Adjustments			Amounts Recognized
		as of Acquisition Date					as of Acquisition Date
		(as previously reported)					(as adjusted)
	Assets
	Cash	$	983	$	—		$	983
	Current and non-current assets	1,385		(18		)	1,367
	Property, plant and equipment	3,936		(27		)	3,909
	Derivative assets	1,157		—			1,157
	Deferred income taxes	2,265		21			2,286
	Total assets acquired	$	9,726	$	(24	)	$	9,702
	Liabilities
	Current and non-current liabilities	$	1,312	$	(7	)	$	1,305
	Out-of-market contracts and leases	1,064		15			1,079
	Derivative liabilities	399		—			399
	Long-term debt and capital leases	4,203		3			4,206
	Total liabilities assumed	6,978		11			6,989
	Net assets acquired	2,748		(35		)	2,713
	Consideration paid	2,188		—			2,188
	Gain on bargain purchase	$	560	$	(35	)	$	525
	2012 Dispositions
	Agua Caliente
	On January 18, 2012, the Company sold a 49% interest in NRG Solar AC Holdings LLC, the indirect owner of the Agua Caliente project, to MidAmerican Energy Holdings Company, or MidAmerican. A majority of the $122 million of cash consideration received at closing represented 49% of construction costs funded by NRG's equity contributions. The excess of the consideration over the carrying value of the divested interest was recorded to additional paid-in capital. MidAmerican will fund its proportionate share of future equity contributions and other credit support for the project. NRG continues to hold a majority interest in and consolidates the project.
	Saale Energie GmbH
	On July 17, 2012, the Company sold its 100% interest in Saale Energie GmbH, which holds a 41.9% interest in Kraftwerke Schkopau GbR and a 44.4% interest in Kraftwerke Schkopau Betriebsgesllschaft mbH, collectively, Schkopau.  Schkopau holds a fixed 400 MW participation in the 900 MW Schkopau Power Station located in Germany.  In connection with the sale of Schkopau, NRG entered into a foreign currency swap contract to hedge the impact of exchange rate fluctuations on the sale proceeds of €141 million. The Company received cash consideration, net of selling expenses, of $174 million, which included $4 million related to the settlement of the swap contract that was recorded as a gain within Other income, net in the quarter ended September 30, 2012.  The cash consideration approximated the book value of the net assets, including cash of $38 million, on the date of the sale.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2013
Fair Value of Financial Instruments Disclosure [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 2012 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, 2013				As of December 31, 2012
		Carrying Amount		Fair Value		Carrying Amount			Fair Value
		(In millions)
	Assets:
	Notes receivable (a)	$	107	$	107	$	88		$	88
	Liabilities:
	Long-term debt, including current portion	16,699		17,061		15,866			16,492
	(a) Includes the current portion of notes receivable which is recorded in prepayments and other current assets 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 1 within the fair value hierarchy. The fair value of 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.
	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, 2013
		Fair Value
	(In millions)	Level 1		Level 2		Level 3			Total
	Investment in available-for-sale securities (classified within other
	non-current assets):
	Debt securities	$	—	$	—	$	15		$	15
	Other (a)	37		—		—			37
	Trust fund investments:
	Cash and cash equivalents	2		—		—			2
	U.S. government and federal agency obligations	51		4		—			55
	Federal agency mortgage-backed securities	—		58		—			58
	Commercial mortgage-backed securities	—		12		—			12
	Corporate debt securities	—		60		—			60
	Equity securities	281		—		55			336
	Foreign government fixed income securities	—		2		—			2
	Derivative assets:
	Commodity contracts	436		1,337		111			1,884
	Interest rate contracts	—		11		—			11
	Total assets	$	807	$	1,484	$	181		$	2,472
	Derivative liabilities:
	Commodity contracts	$	344	$	892	$	118		$	1,354
	Interest rate contracts	—		82		—			82
	Total liabilities	$	344	$	974	$	118		$	1,436
	(a) Primarily consists of mutual funds held in rabbi trusts for non-qualified deferred compensation plans for certain former employees.
		As of December 31, 2012
		Fair Value
	(In millions)	Level 1		Level 2		Level 3			Total
	Investment in available-for-sale securities (classified within other
	non-current assets):
	Debt securities	$	—	$	—	$	12		$	12
	Other (a)	44		—		—			44
	Trust fund investments:
	Cash and cash equivalents	10		—		—			10
	U.S. government and federal agency obligations	34		—		—			34
	Federal agency mortgage-backed securities	—		59		—			59
	Commercial mortgage-backed securities	—		9		—			9
	Corporate debt securities	—		80		—			80
	Equity securities	233		—		47			280
	Foreign government fixed income securities	—		2		—			2
	Derivative assets:
	Commodity contracts	1,457		1,711		135			3,303
	Interest rate contracts	—		3		—			3
	Total assets	$	1,778	$	1,864	$	194		$	3,836
	Derivative liabilities:
	Commodity contracts	$	1,144	$	1,047	$	147		$	2,338
	Interest rate contracts	—		143		—			143
	Total liabilities	$	1,144	$	1,190	$	147		$	2,481
(a) Primarily consists of mutual funds held in rabbi trusts for non-qualified deferred compensation plans for certain former employees.
There were no transfers during the three and nine months ended September 30, 2013 and 2012, between Levels 1 and 2. The following tables reconcile, for the three and nine months ended September 30, 2013 and 2012, the 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:
	Fair Value Measurement Using Significant Unobservable Inputs (Level 3)
	Three months ended September 30, 2013										Nine months ended September 30, 2013
(In millions)	Debt Securities		Trust Fund Investments		Derivatives(a)			Total			Debt Securities		Trust Fund Investments		Derivatives(a)			Total
Beginning balance	$	15	$	50	$	(12	)	$	53		$	12	$	47	$	(12	)	$	47
Total gains/(losses) — realized/unrealized:
Included in earnings	—		—		14			14			—		—		(4		)	(4		)
Included in OCI	—		—		—			—			3		—		—			3
Included in nuclear decommissioning obligations	—		5		—			5			—		7		—			7
Purchases	—		—		4			4			—		1		(3		)	(2		)
Transfers into Level 3 (b)	—		—		(36		)	(36		)	—		—		(9		)	(9		)
Transfers out of Level 3 (b)	—		—		23			23			—		—		21			21
Ending balance as of	$	15	$	55	$	(7	)	$	63		$	15	$	55	$	(7	)	$	63
September 30, 2013
Gains 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, 2013	$	—	$	—	$	(7	)	$	(7	)	$	—	$	—	$	(4	)	$	(4	)
(a)	Consists of derivative assets and liabilities, net.
(b)	Transfers in/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, 2012										Nine months ended September 30, 2012
(In millions)	Debt Securities		Trust Fund Investments		Derivatives(a)			Total			Debt Securities		Trust Fund Investments		Derivatives(a)			Total
Beginning balance	$	9	$	43	$	171		$	223		$	7	$	42	$	8		$	57
Total (losses)/gains — realized/unrealized:
Included in earnings	—		—		(9		)	(9		)	—		—		(3		)	(3		)
Included in OCI	2		—		—			2			4		—		—			4
Included in nuclear decommissioning obligations	—		3		—			3			—		3		—			3
Purchases	—		—		(109		)	(109		)	—		1		(1		)	—
Transfers into Level 3 (b)	—		—		(31		)	(31		)	—		—		4			4
Transfers out of Level 3 (b)	—		—		(20		)	(20		)	—		—		(6		)	(6		)
Ending balance as of	$	11	$	46	$	2		$	59		$	11	$	46	$	2		$	59
September 30, 2012
(Losses)/gains 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, 2012	$	—	$	—	$	(5	)	$	(5	)	$	—	$	—	$	1		$	1
(a)	Consists of derivative assets and liabilities, net.
(b)	Transfers in/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.
Realized and unrealized gains and losses included in earnings that are related to the energy derivatives are recorded in operating revenues and cost of operations.
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. For the majority of NRG's markets, the Company receives quotes from multiple sources. To the extent that NRG receives multiple quotes, the Company's prices reflect the average of the bid-ask mid-point prices obtained from all sources that NRG believes provide the most liquid market for the commodity. If the Company receives one quote, then the mid-point of the bid-ask spread for that quote is used. The terms for which such price information is available vary by commodity, region and product. A significant portion of the fair value of the Company's derivative portfolio is based on price quotes from brokers in active markets who regularly facilitate those transactions and the Company believes such price quotes are executable. The Company does not use third party sources that derive price based on proprietary models or market surveys. 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, 2013, contracts valued with prices provided by models and other valuation techniques make up 6% of the total derivative assets and 8% of the total derivative liabilities.
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. To the extent that NRG's net exposure under a specific master agreement is an asset, the Company uses the counterparty's default swap rate. If the net exposure under a specific master agreement is a liability, the Company uses NRG's default swap rate. The credit reserve is added to the discounted fair value to reflect the exit price that a market participant would be willing to receive to assume NRG's liabilities or that a market participant would be willing to pay for NRG's assets. As of September 30, 2013, the credit reserve resulted in a $1 million decrease in fair value which is composed of a $1 million gain in OCI, and a $2 million loss in operating revenue and cost of operations. As of September 30, 2012, the credit reserve resulted in a $9 million increase in fair value which is composed of a $4 million gain in OCI and a $5 million gain 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 2012 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 monitors and manages counterparty credit risk through credit policies that include: (i) an established credit approval process; (ii) daily monitoring of counterparties' credit limits; (iii) the use of credit mitigation measures such as margin, collateral, prepayment arrangements, or volumetric limits; (iv) the use of payment netting arrangements; and (v) the use of master netting agreements that allow for the netting of positive and negative exposures of various contracts associated with a single counterparty. Risk surrounding counterparty performance and credit could ultimately impact the amount and timing of expected cash flows. The Company seeks to mitigate counterparty credit risk with a diversified portfolio of counterparties. The Company also has credit protection within various agreements to call on additional collateral support if and when necessary. Cash margin is collected and held at NRG to cover the credit risk of the counterparty until positions settle.
As of September 30, 2013, counterparty credit exposure, excluding credit risk exposure under certain long term agreements, was $975 million and NRG held collateral (cash and letters of credit) against those positions of $44 million, resulting in a net exposure of $931 million. Approximately 85% of the Company's exposure before collateral is expected to roll off by the end of 2014. 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)
Category	(% of Total)
Financial institutions	58	%
Utilities, energy merchants, marketers and other	34
ISOs	6
Coal and emissions	2
Total as of September 30, 2013	100	%
	Net Exposure (a)
Category	(% of Total)
Investment grade	96	%
Non-rated (b)	4
Total as of September 30, 2013	100	%
(a)	Counterparty credit exposure excludes uranium and coal transportation contracts because of the unavailability of market prices.
(b)	For non-rated counterparties, a significant portion are related to ISO and municipal public power entities, which are considered investment grade equivalent ratings based on NRG's internal credit ratings.
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 $316 million. 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.
Counterparty credit exposure described above excludes credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations, and solar PPAs. As external sources or observable market quotes are not available to estimate such exposure, the Company values 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, 2013, aggregate credit risk exposure managed by NRG to these counterparties was approximately $2.3 billion, including $649 million related to assets of NRG Yield, Inc., 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, which NRG is unable to predict.
Retail Customer Credit Risk
NRG is exposed to retail credit risk through the Company's retail electricity providers, which serve commercial, industrial and governmental/institutional customers and the Mass market. Retail credit risk results when a customer fails to pay for products or services rendered. The losses may result from both nonpayment of customer accounts receivable and the loss of in-the-money forward value. NRG 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, 2013, the Company's retail customer credit exposure was diversified across many customers and various industries, as well as government entities.

Nuclear_Decommissioning_Trust_

Nuclear Decommissioning Trust Fund	9 Months Ended
	Sep. 30, 2013
Nuclear Decommissioning Trust Fund Disclosure [Abstract]	'
Nuclear Decommissioning Trust Fund	'
	Nuclear Decommissioning Trust Fund
	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 nuclear decommissioning trust liability and are not included in net income or accumulated other comprehensive income, 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, 2013							As of December 31, 2012
	(In millions, except otherwise noted)	Fair Value		Unrealized Gains		Unrealized Losses		Weighted-average Maturities (In years)	Fair Value		Unrealized Gains (a)		Weighted-average Maturities (In years)
	Cash and cash equivalents	$	2	$	—	$	—	—	$	10	$	—	—
	U.S. government and federal agency obligations	54		2		1		9	33		2		10
	Federal agency mortgage-backed securities	58		1		1		24	59		2		23
	Commercial mortgage-backed securities	12		—		—		29	9		—		30
	Corporate debt securities	60		2		1		9	80		4		11
	Equity securities	336		187		—		—	280		143		—
	Foreign government fixed income securities	2		—		—		9	2		—		6
	Total	$	524	$	192	$	3		$	473	$	151
	(a)There were no unrealized losses as of December 31, 2012.
	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,
		2013		2012
		(In millions)
	Realized gains	$	10	$	8
	Realized losses	7		5
	Proceeds from sale of securities	344		316

Accounting_for_Derivative_Inst

Accounting for Derivative Instruments and Hedging Activities	9 Months Ended
	Sep. 30, 2013
Accounting for 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 2012 Form 10-K.
	Energy-Related Commodities
	As of September 30, 2013, NRG had energy-related derivative financial instruments extending through 2015, which are designated as cash flow hedges.
	Interest Rate Swaps
	NRG is exposed to changes in interest rates through the Company's issuance of variable and fixed rate debt. In order to manage the Company's interest rate risk, NRG enters into interest rate swap agreements. As of September 30, 2013, the Company had interest rate derivative instruments on non-recourse debt extending through 2030, the majority of which are designated as cash flow hedges.
	Volumetric Underlying Derivative Transactions
	The following table summarizes the net notional volume buy/(sell) of NRG's open derivative transactions broken out by commodity, excluding those derivatives that qualified for the NPNS exception as of September 30, 2013 and December 31, 2012. 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, 2013				December 31, 2012
	Commodity	Units	(In millions)
	Emissions	Short Ton	(1		)		(1		)
	Coal	Short Ton	42				37
	Natural Gas	MMBtu	(215		)		(413		)
	Oil	Barrel	—				1
	Power	MWh	(16		)		(14		)
	Interest	Dollars	$	1,520			$	2,612
	The decrease in the natural gas position was the result of additional purchases entered into during the year to hedge our retail portfolio as well as the settlement of positions during the period.  These amounts were slightly offset by natural gas sales entered into during the year to hedge our conventional power generation.  The decrease in the interest rate position was primarily the result of the settlement of interest rate swaps.
	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, 2013				December 31, 2012				September 30, 2013				December 31, 2012
		(In millions)
	Derivatives designated as cash flow hedges:
	Interest rate contracts current	$	—			$	—			$	27			$	29
	Interest rate contracts long-term	8				3				47				96
	Commodity contracts current	—				—				2				3
	Commodity contracts long-term	—				—				1				1
	Total derivatives designated as cash flow hedges	8				3				77				129
	Derivatives not designated as cash flow hedges:
	Interest rate contracts current	—				—				5				7
	Interest rate contracts long-term	3				—				3				11
	Commodity contracts current	1,389				2,644				1,030				1,942
	Commodity contracts long-term	495				659				321				392
	Total derivatives not designated as cash flow hedges	1,887				3,303				1,359				2,352
	Total derivatives	$	1,895			$	3,306			$	1,436			$	2,481
	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, 2013		(In millions)
	Commodity contracts:
	Derivative assets		$	1,884			$	(1,151	)		$	(195	)		$	538
	Derivative liabilities		(1,354		)		1,151				65				(138		)
	Total commodity contracts		530				—				(130		)		400
	Interest rate contracts:
	Derivative assets		11				(6		)		—				5
	Derivative liabilities		(82		)		6				—				(76		)
	Total interest rate contracts		(71		)		—				—				(71		)
	Total derivative instruments		$	459			$	—			$	(130	)		$	329
			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, 2012		(In millions)
	Commodity contracts:
	Derivative assets		$	3,303			$	(2,024	)		$	(374	)		$	905
	Derivative liabilities		(2,338		)		2,024				28				(286		)
	Total commodity contracts		965				—				(346		)		619
	Interest rate contracts:
	Derivative assets		3				—				—				3
	Derivative liabilities		(143		)		—				—				(143		)
	Total interest rate contracts		(140		)		—				—				(140		)
	Total derivative instruments		$	825			$	—			$	(346	)		$	479
	Accumulated Other Comprehensive Income
The following table summarizes the effects of ASC 815, Derivatives and Hedging, or ASC 815, on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax:
	Three months ended September 30, 2013												Nine months ended September 30, 2013
	Energy Commodities				Interest Rate				Total				Energy Commodities				Interest Rate			Total
	(In millions)
Accumulated OCI beginning balance	$	24			$	(31	)		$	(7	)		$	41			$	(72	)	$	(31	)
Reclassified from accumulated OCI to income:
Due to realization of previously deferred amounts	(15		)		2				(13		)		(38		)		6			(32		)
Mark-to-market of cash flow hedge accounting contracts	1				(4		)		(3		)		7				33			40
Accumulated OCI ending balance, net of $13 tax	$	10			$	(33	)		$	(23	)		$	10			$	(33	)	$	(23	)
Gains/(losses) expected to be realized from OCI during the next 12 months, net of $1 tax	$	11			$	(9	)		$	2			$	11			$	(9	)	$	2
Gains recognized in income from the ineffective portion of cash flow hedges	$	1			$	—			$	1			$	—			$	—		$	—
	Three months ended September 30, 2012												Nine months ended September 30, 2012
	Energy Commodities				Interest Rate				Total				Energy Commodities				Interest Rate			Total
	(In millions)
Accumulated OCI beginning balance	$	111			$	(68	)		$	43			$	188			$	(56	)	$	132
Reclassified from accumulated OCI to income:
Due to realization of previously deferred amounts	(30		)		3				(27		)		(106		)		11			(95		)
Mark-to-market of cash flow hedge accounting contracts	(1		)		(15		)		(16		)		(2		)		(35		)	(37		)
Accumulated OCI ending balance, net of $12 tax	$	80			$	(80	)		$	—			$	80			$	(80	)	$	—
Gains/(losses) expected to be realized from OCI during the next 12 months, net of $38 tax	$	77			$	(11	)		$	66			$	77			$	(11	)	$	66
Losses recognized in income from the ineffective portion of cash flow hedges	$	—			$	—			$	—			$	(51	)		$	—		$	(51	)
Amounts reclassified from accumulated OCI into income and amounts recognized in income from the ineffective portion of cash flow hedges are recorded to operating revenue for commodity contracts and interest expense for interest rate contracts.
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 and ineffectiveness of hedge derivatives are reflected in current period earnings.
The following table summarizes the 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 effect of commodity hedges is included within operating revenues and cost of operations and the effect of interest rate hedges is included in interest expense.
	Three months ended September 30,								Nine months ended September 30,
	2013				2012				2013				2012
Unrealized mark-to-market results	(In millions)
Reversal of previously recognized unrealized gains on settled positions related to economic hedges	$	(48	)		$	(85	)		$	(80	)		$	(160	)
Reversal of (gain)/loss positions acquired as part of the Reliant Energy, Green Mountain Energy and GenOn acquisitions	(82		)		(15		)		(269		)		5
Net unrealized gains/(losses) on open positions related to economic hedges	76				(159		)		131				(78		)
Gains/(losses) on ineffectiveness associated with open positions treated as	1				—				—				(51		)
cash flow hedges
Total unrealized mark-to-market losses for economic hedging activities	(53		)		(259		)		(218		)		(284		)
Reversal of previously recognized unrealized gains on settled positions related to trading activity	(13		)		(15		)		(42		)		(45		)
Reversal of gain positions acquired as part of the GenOn acquisitions	(2		)		—				(2		)		—
Net unrealized gains/(losses) on open positions related to trading activity	26				(3		)		—				33
Total unrealized mark-to-market gains/(losses) for trading activity	11				(18		)		(44		)		(12		)
Total unrealized losses	$	(42	)		$	(277	)		$	(262	)		$	(296	)
	Three months ended September 30,								Nine months ended September 30,
	2013				2012				2013				2012
	(In millions)
Unrealized losses included in operating revenues	$	(64	)		$	(395	)		$	(404	)		$	(470	)
Unrealized gains included in cost of operations	22				118				142				174
Total impact to statement of operations — energy commodities	$	(42	)		$	(277	)		$	(262	)		$	(296	)
Total impact to statement of operations — interest rate contracts	$	4			$	—			$	10			$	(12	)
The reversal of gain or loss positions acquired as part of the Reliant Energy, Green Mountain Energy and GenOn acquisitions were valued based upon the forward prices on the acquisition dates.
For the nine months ended September 30, 2013, the unrealized gain from open economic hedge positions was primarily the result of an increase in value of forward sales of natural gas and electricity due to a decrease in forward natural gas and electricity prices.
As of June 30, 2013, NRG had interest rate swaps designated as cash flow hedges on the CVSR solar project. The notional amount on the swaps exceeded the actual debt draws on the project. As such, NRG discontinued cash flow hedge accounting for these contracts and $5 million of loss previously deferred in OCI was recognized in earnings for the nine months ended September 30, 2013.
For the nine months ended September 30, 2012, the unrealized loss from open economic hedge positions was primarily the result of a decrease in forward coal prices.
As of June 30, 2012, NRG had interest rate swaps designated as cash flow hedges on the Alpine solar project. The notional amount on the swaps exceeded the actual debt draws on the project. As such, NRG discontinued cash flow hedge accounting for these contracts and $4 million of loss previously deferred in OCI was recognized in earnings for the nine months ended September 30, 2012.
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 requires 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, 2013 was $103 million. The collateral required for contracts with credit rating contingent features was $39 million. The Company is also a party to certain marginable agreements where NRG has a net liability position, but the counterparty has not called for the collateral due, which was approximately $15 million as of September 30, 2013.
See Note 4, Fair Value of Financial Instruments, to this Form 10-Q for discussion regarding concentration of credit risk.

Debt_and_Capital_Leases

Debt and Capital Leases	9 Months Ended
	Sep. 30, 2013
Long Term Debt Disclosure [Abstract]	'
Debt and Capital Leases	'
	Debt and Capital Leases
	This footnote should be read in conjunction with the complete description under Note 11, Debt and Capital Leases, to the Company's 2012 Form 10-K.
	Long-term debt and capital leases consisted of the following:
		September 30, 2013		December 31, 2012		Current interest rate % (a)
	(In millions, except rates)
	NRG recourse debt:
	Senior notes, due 2018	$	1,130	$	1,200	7.625
	Senior notes, due 2019	800		800		7.625
	Senior notes, due 2019	601		693		8.5
	Senior notes, due 2020	1,063		1,100		8.25
	Senior notes, due 2021	1,128		1,128		7.875
	Senior notes, due 2023	990		990		6.625
	Term loan facility, due 2018	2,006		1,573		L+2.00
	Indian River Power LLC, tax-exempt bonds, due 2040 and 2045	247		247		5.375 - 6.000
	Dunkirk Power LLC, tax-exempt bonds, due 2042	59		59		5.875
	Fort Bend County, tax-exempt bonds, due 2038 and 2042	67		28		4.75
	Subtotal NRG Recourse Debt	8,091		7,818
	NRG non-recourse debt:
	GenOn senior notes, due 2014	—		617		7.625
	GenOn senior notes, due 2017	787		800		7.875
	GenOn senior notes, due 2018	785		801		9.5
	GenOn senior notes, due 2020	624		631		9.875
	GenOn Americas Generation senior notes, due 2021	504		509		8.5
	GenOn Americas Generation senior notes, due 2031	435		437		9.125
	NRG Marsh Landing, due 2017 and 2023	500		390		L+2.50 - 2.75
	CVSR - High Plains Ranch II LLC, due 2013 and 2037	1,104		786		0.611 - 3.579
	NRG West Holdings LLC, due 2023	475		350		L+2.25 - 2.75
	Agua Caliente Solar LLC, due 2037	764		640		2.395 - 3.473
	Ivanpah Financing, due 2014 and 2038	1,561		1,437		1.116 - 4.256
	South Trent Wind LLC, due 2020	69		72		L+2.625
	NRG Peaker Finance Co. LLC, bonds, due 2019	176		173		L+1.07
	NRG Energy Center Minneapolis LLC, senior secured notes, due 2013, 2017 and 2025	129		137		5.95 - 7.25
	NRG Solar Alpine LLC, due 2013 and 2022	223		2		L+2.25 - 2.50
	NRG Solar Borrego I LLC, due 2024 and 2038	79		—		L+2.50/5.65
	NRG Solar Avra Valley LLC	64		66		L+2.25
	TA - High Desert LLC, due 2013, 2023 and 2033	82		—		L+2.50/5.15
	NRG Solar Kansas South LLC, due 2013 and 2031	59		—		L+2.00 - 2.625
	Other	188		200		various
	Subtotal NRG Non-Recourse Debt	8,608		8,048
	Subtotal long-term debt (including current maturities)	16,699		15,866
	Capital leases:
	Chalk Point capital lease, due 2015	11		14		8.19
	Other	3		3		various
	Subtotal long-term debt and capital leases (including current maturities)	16,713		15,883
	Less current maturities	911		147
	Total long-term debt and capital leases	$	15,802	$	15,736
	(a) As of September 30, 2013, L+ equals 3 month LIBOR plus x%, with the exception of NRG Solar Alpine LLC cash grant loan and NRG Solar Kansas South LLC cash grant bridge loan which are 1 month LIBOR plus x% and NRG Solar Kansas South LLC term loan which is 6 month LIBOR plus x%.
	NRG Recourse Debt
	Senior Credit Facility
	On June 4, 2013, NRG amended the Term Loan Facility to (i) obtain additional financing of $450 million, which was issued at a discount of 99.5%; and (ii) adjust the interest rate from LIBOR plus 2.50% to LIBOR plus 2.00%. In addition, the Company redeemed and re-issued $407 million of the Term Loan Facility to new lenders resulting in a $7 million loss on debt extinguishment, recorded during the three months ended June 30, 2013, which primarily consisted of the write-off of previously deferred financing costs and unamortized discount. The proceeds from the additional $450 million borrowed were used for general corporate purposes. Debt issuance costs of $23 million and a discount on debt issuance of $4 million will be amortized to interest expense through the maturity date of the Term Loan Facility.
	The Company also amended the Revolving Credit Facility to (i) increase the capacity by $211 million to a total of $2.5 billion; (ii) adjust the interest rate to LIBOR plus 2.25%; and (iii) extend the maturity date to July 1, 2018 to coincide with the maturity date of the Term Loan Facility. As a result of the amended Revolving Credit Facility, the Company capitalized debt issuance costs of $4 million, which will be amortized to interest expense through the maturity date of the Revolving Credit Facility. A $3 million loss on debt extinguishment was recorded during the three months ended June 30, 2013 related to the write-off of previously deferred financing costs.
	Senior Notes Repurchases
	On December 17, 2012, NRG entered into an agreement with a financial institution to repurchase up to $200 million of the Senior Notes in the open market by February 27, 2013.  In the first quarter of 2013, the Company paid $80 million, $104 million, and $42 million, at an average price of 114.179%, 111.700%, and 113.082% of face value, for repurchases of the Company's 2018 Senior Notes, 2019 Senior Notes and 2020 Senior Notes, respectively. A $28 million loss on the debt extinguishment of the 2018 Senior Notes, 2019 Senior Notes and 2020 Senior Notes was recorded during the three months ended March 31, 2013 which primarily consisted of the premiums paid on the repurchases and the write-off of previously deferred financing costs.
	NRG Non-Recourse Debt
	Redemption of GenOn Senior Notes
	In June 2013, the Company redeemed all of the 2014 GenOn Senior Notes with an aggregate outstanding principal amount of $575 million at a redemption price of 106.778% of face value as well as any accrued and unpaid interest as of the redemption date. In connection with the redemption, an $11 million loss on the debt extinguishment of the 2014 GenOn Senior Notes was recorded during the three months ended June 30, 2013 which primarily consisted of a make whole premium payment offset by the write-off of unamortized premium.
	Kansas South Facility
	In the second quarter of 2013, the Company, through its wholly owned subsidiary, NRG Solar PV LLC, acquired Kansas South, a 20 MW utility-scale photovoltaic solar facility located in Kings County, California, shortly before commercial operation. In June 2013, NRG recorded $59 million of non-recourse project level debt under the Kansas South Facility which includes a $38 million term loan due 2031 and a $21 million cash grant bridge loan due the earlier of 10 days after receipt of the cash grant or March 2014. The term loan has an interest rate of 6 month LIBOR plus an applicable margin of 2.625% and increases by 0.25% every four years. The cash grant bridge loan has an interest rate of 1 month LIBOR plus an applicable margin of 2.00%. The term loan amortizes on a predetermined schedule and is secured by all of the assets of Kansas South. As of September 30, 2013, $4 million of letters of credit were issued under the Kansas South Facility.
	NRG Repowering Holdings LLC Facility
	In June 2013, $82 million of letters of credit issued under the NRG Repowering Holdings LLC Facility were returned to the Company. In July 2013, the NRG Repowering Holding LLC Facility was terminated and the Company issued replacement letters of credit under its Revolving Credit Facility.
	Marsh Landing Credit Agreement Term Conversion
	In May 2013, Marsh Landing met the conditions under the credit agreement to convert the construction loan for the facility to a term loan, which will amortize on a predetermined basis. Prior to term conversion, the Company drew the remaining funds available under the facility in order to pay costs due for construction. The Company issued a $26 million letter of credit under the facility in support of its debt service requirements.
	Alpine Financing
In March 2012, NRG Solar Alpine LLC, or Alpine, entered into a credit agreement with a group of lenders for a $166 million construction loan that will convert to a term loan upon completion of the project and a $68 million cash grant loan. In January 2013, the credit agreement was amended reducing the cash grant loan to $63 million. In March 2013, Alpine met the conditions under the credit agreement to convert the construction loan for the facility to a term loan. Immediately prior to the conversion, the Company drew an additional $164 million under the construction loan and $62 million under the cash grant loan. The term loan amortizes on a predetermined schedule with final maturity in November 2022. As of September 30, 2013, $161 million was outstanding under the term loan, $62 million under the cash grant loan, and $37 million of letters of credit were issued under the credit agreement.
Borrego Financing
In March 2013, NRG Solar Borrego I LLC, or Borrego, entered into a credit agreement with a group of lenders, or the Borrego Financing Agreement, for $45 million of 5.65% fixed rate notes and a $36 million term loan. The term loan has an interest rate of 3 month LIBOR plus an applicable margin of 2.50%, which escalates 0.25% on the fourth and eighth anniversary of the closing date. The fixed rate notes mature in February 2038 and the term loan matures in December 2024. Both amortize based upon predetermined schedules. The Borrego Financing Agreement also includes a letter of credit facility on behalf of Borrego of up to $5 million. Borrego pays an availability fee of 100% of the applicable margin on issued letters of credit. As of September 30, 2013, $45 million was outstanding under the fixed rate notes, $34 million was outstanding under the term loan, and $5 million of letters of credit in support of the project were issued.
Under the terms of the Borrego Financing Agreement, on March 28, 2013, Borrego was required to enter into two fixed for floating interest rate swaps that would fix the interest rate for a minimum of 75% of the outstanding notional amount. Borrego will pay its counterparty the equivalent of a 1.125% fixed interest payment on a predetermined notional value, and Borrego will receive quarterly the equivalent of a floating interest payment based on a 3 month LIBOR calculated on the same notional value through June 30, 2020. All interest rate swap payments by Borrego and its counterparties are made quarterly and the LIBOR rate is determined in advance of each interest period. The original notional amount of the swaps, which became effective April 3, 2013, is $15 million and will amortize in proportion to the term loan.
High Desert Facility
In the first quarter of 2013, the Company, through its wholly owned subsidiary, NRG Solar PV LLC, acquired High Desert, a 20 MW utility-scale photovoltaic solar facility located in Lancaster, California, shortly before commercial operation.  As part of the acquisition of High Desert, NRG recorded $82 million of non-recourse project level debt in March 2013 issued under the High Desert Facility which is comprised of $53 million of fixed rate notes due 2033 at an interest rate of 5.15%, $7 million of floating rate notes due 2023, $22 million of bridge notes due the earlier of 10 days after receipt of the cash grant or February 2014 and a revolving facility of $12 million. The floating rate notes, bridge notes and revolving facility have an interest rate of 3 month LIBOR plus 2.50%. The revolving facility can be used for cash or for the issuance of up to $9 million in letters of credit. As of September 30, 2013, $9 million of letters of credit were issued under the revolving facility.  The notes amortize on predetermined schedules and are secured by all of the assets of High Desert.
NRG Yield Revolving Credit Facility
In connection with the initial public offering of Class A common stock of NRG Yield, Inc. in July 2013, as further described in Note 1, Basis of Presentation, NRG Yield LLC and its direct wholly owned subsidiary, NRG Yield Operating LLC, entered into a senior secured revolving credit facility, which provides a revolving line of credit of $60 million. The NRG Yield revolving credit facility can be used for cash or for the issuance of letters of credit. There was no cash drawn or letters of credit issued under the NRG Yield revolving credit facility as of September 30, 2013.

Variable_Interest_Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2013
Variable Interest Entities Disclosure [Abstract]	'
Variable Interest Entity	'
	Variable Interest Entities
	NRG has interests in entities that are considered VIEs under ASC 810, Consolidation, but NRG is not considered the primary beneficiary.  NRG accounts for its interests in these entities under the equity method of accounting.
	GenConn Energy LLC — Through its subsidiary, NRG Connecticut Peaking Development LLC, NRG owns a 50% interest in GenConn, a limited liability company which owns and operates two 190 MW peaking generation facilities in Connecticut at NRG's Devon and Middletown sites. NRG's maximum exposure to loss is limited to its equity investment, which was $118 million as of September 30, 2013.
	Sherbino I Wind Farm LLC — NRG owns a 50% interest in Sherbino, a joint venture with BP Wind Energy North America Inc. NRG's maximum exposure to loss is limited to its equity investment, which was $88 million as of September 30, 2013.
	Texas Coastal Ventures LLC — NRG owns a 50% interest in Texas Coastal Ventures, a joint venture with Hilcorp Energy I, L.P., through its subsidiary Petra Nova LLC. NRG's maximum exposure to loss is limited to its equity investment, which was $63 million as of September 30, 2013.

Changes_in_Capital_Structure

Changes in Capital Structure	9 Months Ended
	Sep. 30, 2013
Changes in Capital Structure Disclosure [Abstract]	'
Changes in Capital Structure	'
	Changes in Capital Structure
	As of September 30, 2013 and December 31, 2012, the Company had 500,000,000 shares of common stock authorized. The following table reflects the changes in NRG's common shares issued and outstanding:
		Issued		Treasury			Outstanding
	Balance as of December 31, 2012	399,112,616		(76,505,718	)		322,606,898
	Shares issued under LTIP	1,562,480		—			1,562,480
	Shares issued under ESPP	—		130,482			130,482
	Shares repurchased under Capital Allocation Program	—		(972,292	)		(972,292	)
	Balance as of September 30, 2013	400,675,096		(77,347,528	)		323,327,568
	As discussed in Note 3, Business Acquisition and Dispositions, the Company announced its intention to issue 12,671,977 shares of NRG common stock in connection with the acquisition of EME, expected to close in the first quarter of 2014.
	2013 Capital Allocation Program
	In 2013, the Company increased its annual common stock dividend by 33%, to $0.48 per share. The following table lists the dividends paid during 2013:
		First Quarter 2013			Second Quarter 2013				Third Quarter 2013
	Dividends per Common Share	$	0.09		$	0.12			$	0.12
	On October 16, 2013, NRG declared a quarterly dividend on the Company's common stock of $0.12 per share, payable on November 15, 2013, to shareholders of record as of November 1, 2013.
	In addition, the Company is authorized to repurchase $200 million of its common stock in 2013 under the 2013 Capital Allocation Program. During the first quarter, the Company purchased 972,292 shares of NRG common stock for approximately $25 million at an average cost of $25.88 per share. As a result of the proposed acquisition of EME, the Company has not completed the remaining $175 million of share repurchases under the 2013 Capital Allocation Program and does not expect to do so through the remainder of the 2013 fiscal year.
	The Company's common stock dividend and share repurchases are subject to available capital, market conditions, and compliance with associated laws and regulations.

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2013
Earnings (Loss) Per Share Disclosure [Abstract]	'
Earnings Per Share	'
	Earnings/(Loss) Per Share
	Basic earnings/(loss) per common share is computed by dividing net income/(loss) less accumulated preferred stock dividends 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 earnings/(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 earnings/(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)	2013			2012			2013			2012
	Basic earnings/(loss) per share attributable to NRG common stockholders
	Net income/(loss) attributable to NRG Energy, Inc.	$	124		$	(1	)	$	(74	)	$	43
	Dividends for preferred shares	2			2			7			7
	Income/(loss) Available for Common Stockholders	$	122		$	(3	)	$	(81	)	$	36
	Weighted average number of common shares outstanding	323			228			323			228
	Earnings/(loss) per weighted average common share — basic	$	0.38		$	(0.01	)	$	(0.25	)	$	0.16
	Diluted earnings/(loss) per share attributable to NRG common stockholders
	Weighted average number of common shares outstanding	323			228			323			228
	Incremental shares attributable to the issuance of equity compensation (treasury stock method)	4			—			—			2
	Total dilutive shares	327			228			323			230
	Earnings/(loss) per weighted average common share — diluted	$	0.37		$	(0.01	)	$	(0.25	)	$	0.16
	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 earnings/(loss) per share:
		Three months ended September 30,					Nine months ended September 30,
	(In millions of shares)	2013		2012			2013		2012
	Equity compensation plans	2		11			10		6
	Embedded derivative of 3.625% redeemable perpetual preferred stock	16		16			16		16
	Total	18		27			26		22

Segment_Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2013
Segment Reporting Disclosure [Abstract]	'
Segment Reporting	'
	Segment Reporting
	Effective June 2013, the Company's segment structure and its allocation of corporate expenses were updated to reflect how management currently makes financial decisions and allocates resources. The Company has recast data from prior periods to reflect this change in reportable segments to conform to the current year presentation. The Company's businesses are primarily segregated based on the Retail Business, conventional power generation, alternative energy businesses, NRG Yield, and corporate activities.  Within NRG's conventional power generation, there are distinct components with separate operating results and management structures for the following geographical regions: Texas, East, South Central, West and Other, which includes international businesses and maintenance services.  The Company's alternative energy segment includes solar and wind assets, excluding those in the NRG Yield segment, electric vehicle services and the carbon capture business.  NRG Yield includes certain of the Company's contracted generation assets including three natural gas or dual-fired facilities, eight utility-scale solar and wind generation facilities, two portfolios of distributed solar facilities and thermal infrastructure assets. Intersegment sales are accounted for at market.
	(In millions)				Conventional Power Generation
	Three months ended September 30, 2013	Retail(a)			Texas(a)			East(a)			South(a)		West(a)			Other(a)		Alternative Energy(a)			NRG Yield(a)			Corporate(a)(b)			Elimination			Total
											Central
	Operating revenues	$	1,994		$	881		$	1,011		$	244	$	134		$	38	$	83		$	95		$	—		$	(990	)	$	3,490
	Depreciation and amortization	37			116			79			24		13			1		27			16			5			—			318
	Equity in earnings/(losses) of unconsolidated affiliates	—			—			—			1		(10		)	—		(3		)	12			—			(5		)	(5		)
	(Loss)/income before income taxes	(60		)	265			245			17		30			1		1			45			(217		)	(21		)	306
	Net (loss)/income attributable to NRG Energy, Inc.	$	(60	)	$	265		$	245		$	17	$	30		$	1	$	(21	)	$	31		$	(375	)	$	(9	)	$	124
	Total assets as of September 30, 2013	$	4,296		$	11,914		$	8,329		$	2,290	$	1,553		$	461	$	6,162		$	2,331		$	4,863		$	(7,336	)	$	34,863
	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	2		$	910		$	55		$	—	$	—		$	15	$	8		$	—		$	—
	(b) Includes loss on debt extinguishment of $1 million.
	(In millions)				Conventional Power Generation
	Three months ended September 30, 2012	Retail(c)			Texas(c)			East(c)			South(c)		West(c)			Other(c)		Alternative Energy(c)			NRG Yield(c)			Corporate(c)(d)			Elimination			Total
											Central
	Operating revenues	$	1,856		$	877		$	274		$	270	$	87		$	28	$	49		$	47		$	4		$	(1,161	)	$	2,331
	Depreciation and amortization	41			115			32			23		3			1		15			6			3			—			239
	Equity in earnings/(losses) of unconsolidated affiliates	—			—			—			—		4			3		(9		)	6			—			—			4
	(Loss)/income before income taxes	(300		)	299			30			19		35			5		(8		)	12			(197		)	—			(105		)
	Net (loss)/income attributable to NRG Energy, Inc.	$	(300	)	$	299		$	30		$	19	$	35		$	5	$	(16	)	$	4		$	(77	)	$	—		$	(1	)
	(c) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	3		$	1,126		$	6		$	—	$	—		$	12	$	10		$	—		$	4
	(d) Includes loss on debt extinguishment of $41 million.
	(In millions)				Conventional Power Generation
	Nine months ended September 30, 2013	Retail(e)			Texas(e)			East(e)			South(e)		West(e)			Other(e)		Alternative Energy(e)			NRG Yield(e)			Corporate(e)(f)			Elimination			Total
											Central
	Operating revenues	$	4,760		$	1,712		$	2,432		$	656	$	347		$	110	$	177		$	227		$	9		$	(1,930	)	$	8,500
	Depreciation and amortization	105			340			236			73		37			3		78			35			14			—			921
	Equity in (losses)/earnings of unconsolidated affiliates	—			—			—			3		(8		)	2		(7		)	18			—			(2		)	6
	Income/(loss) before income taxes	231			14			238			17		62			3		(48		)	90			(695		)	(6		)	(94		)
	Net income/(loss) attributable to NRG Energy, Inc.	$	231		$	14		$	238		$	17	$	62		$	2	$	(75	)	$	76		$	(642	)	$	3		$	(74	)
	(e) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	4		$	1,732		$	99		$	16	$	3		$	48	$	19		—		$	9
	(f) Includes loss on debt extinguishment of $50 million.
	(In millions)				Conventional Power Generation
	Nine months ended September 30, 2012	Retail(g)			Texas(g)			East(g)			South(g)		West			Other(g)		Alternative Energy(g)			NRG Yield(g)			Corporate(g)(h)			Elimination			Total
											Central
	Operating revenues	$	4,492		$	1,462		$	598		$	653	$	185		$	152	$	91		$	133		$	11		$	(1,418	)	$	6,359
	Depreciation and amortization	126			343			96			69		8			1		34			18			8			—			703
	Equity in earnings/(losses) of unconsolidated affiliates	—			—			—			—		6			8		(3		)	15			—			$	—		$	26
	Income/(loss) before income taxes	504			(202		)	(31		)	—		42			22		(27		)	18			(511		)	—			(185		)
	Net income/(loss) attributable to NRG Energy, Inc.	$	504		$	(202	)	$	(31	)	$	—	$	42		$	18	$	(45	)	$	8		$	(251	)	$	—		$	43
	(g) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	3		$	1,287		$	51		$	—	$	—		$	55	$	18		$	—		$	4
	(h) Includes loss on debt extinguishment of $41 million.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2013
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 otherwise noted)	2013			2012			2013		2012
	Income/(loss) before income taxes	$	306		$	(105	)	(94	)	$	(185	)
	Income tax expense/(benefit)	163			(113		)	(47	)	(246		)
	Effective tax rate	53.3		%	107.6		%	50	%	133		%
	For the three months ended September 30, 2013, NRG's overall effective tax rate was different than the statutory rate of 35% primarily due to the impact of state and local income taxes. For the nine months ended September 30, 2013, NRG's overall effective rate was different than the statutory rate of 35% primarily due to the recognition of ITCs from the Company's Agua Caliente solar project in Arizona and the impact of non-taxable equity earnings, partially offset by state and local income taxes.
	For the three and nine months ended September 30, 2012, NRG's overall effective tax rate was different than the statutory rate of 35% primarily due to the recognition of ITCs from the Company's Agua Caliente solar project in Arizona and production tax credits generated from certain Texas wind facilities.
	Uncertain Tax Benefits
	As of September 30, 2013, NRG has recorded a non-current tax liability of $74 million for uncertain tax benefits from positions taken on various state income tax returns, including accrued interest. NRG has accrued interest related to these uncertain tax benefits of $1 million for the nine months ended September 30, 2013, and has accrued $17 million of interest and penalties since adoption. 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 not subject to U.S. federal income tax examinations for years prior to 2007. With few exceptions, state and local income tax examinations are no longer open for years before 2004. The Company's primary foreign operations are also no longer subject to examination by local jurisdictions for years prior to 2010.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	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 acquisition and assets held by NRG Yield, Inc., 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, 2013, hedges under the first lien were in-the-money for NRG on a counterparty aggregate basis.
	Nuclear Insurance
	STP maintains required insurance coverage for liability claims arising from nuclear incidents pursuant to the Price-Anderson Amendment to the Energy Policy Act of 2005, referred to as the Price-Anderson Act. As of September 30, 2013, the liability limit per incident was $13.6 billion, subject to changes to account for the effects of inflation and the number of licensed reactors. Under the Price-Anderson Act, owners of nuclear power plants in the U.S. are required to purchase primary insurance limits of $375 million for each operating site. In addition, the Price-Anderson Act requires an additional layer of protection through mandatory participation in a retrospective rating plan for power reactors resulting in an additional $13.2 billion in funds available for public liability claims. The current maximum assessment per incident, per reactor, is approximately $127 million, taking into account a 5% adjustment for administrative fees, payable at no more than approximately $19 million per year, per reactor. NRG would be responsible for 44% of the maximum assessment, or $8 million per year, per reactor, and a maximum of $112 million per incident. In addition, the U.S. Congress retains the ability to impose additional financial requirements on the nuclear industry to pay liability claims that exceed $13.6 billion for a single incident. The liabilities of the co-owners of STP with respect to the retrospective premium assessments for nuclear liability insurance are joint and several.
	STP purchases insurance for property damage and site decontamination cleanup costs from Nuclear Electric Insurance Limited, or NEIL, an industry mutual insurance company, of which STP is a member. STP has purchased $2.75 billion in limits for nuclear events and $1.5 billion in limits for non-nuclear events, the maximum available from NEIL. The upper $1 billion in limits (excess of the first $1.75 billion in limits) is a single limit blanket policy shared with two Diablo Canyon nuclear reactors, which have no affiliation with the Company. This shared limit is not subject to automatic reinstatement in the event of a loss. The NEIL policy covers both nuclear and non-nuclear property damage events. NRG also purchases an Accidental Outage policy from NEIL, which provides protection for lost revenue due to an insurable event. This coverage allows for reimbursement up to $1.98 million per week per unit up to a maximum of $215.6 million nuclear and $144 million non-nuclear, and is subject to an eight week waiting period. Under the terms of the NEIL policies, member companies may be assessed up to ten times their annual premium if the NEIL Board of Directors determines their surplus has been depleted due to the payment of property losses at any of the licensed reactors in a single policy year. NEIL requires that its members maintain an investment grade credit rating or insure their annual retrospective obligation by providing a financial guarantee, letter of credit, deposit premium, or an insurance policy. NRG has purchased an insurance policy from NEIL to guarantee the Company's obligation; however this insurance will only respond to retrospective premium adjustments assessed within twenty-four months after the policy term, whereas NEIL's Board of Directors can make such an adjustment up to six years after the policy expires.
	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. 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.
	Louisiana Generating, LLC
	In 2009, the U.S. DOJ, on behalf of the EPA, and later the Louisiana Department of Environmental Quality, or LDEQ, on behalf of the State of Louisiana, sued Louisiana Generating, LLC, or LaGen, a wholly owned subsidiary of NRG, in federal district court in the Middle District of Louisiana alleging violations of the CAA at the Big Cajun II power plant. On March 6, 2013, the court entered a Consent Decree resolving the matter. In addition to a fine of $3.5 million and mitigation projects totaling $10.5 million, the Consent Decree includes: (i) annual emission caps for NOx and SO2; (ii) installation of selective non-catalytic reduction on Units 1, 2 and 3 by May 1, 2014; (iii) installation of dry sorbent injection on Unit 1 by April 15, 2015 followed by a further reduction in SO2 in March 2025; (iv) conversion of Unit 2 to natural gas; and (v) surrender of any excess allowances associated with the NRG owned portion of the plant. Further discussion of this matter can be found in Note 15, Environmental Matters - South Central Region.
	In a related matter, soon after the filing of the above referenced U.S. DOJ lawsuit, LaGen sought insurance coverage from its insurance carrier, Illinois Union Insurance Company, or ILU. ILU denied coverage and refused to provide a defense for LaGen, and thereafter LaGen filed a lawsuit in federal district court in the Middle District of Louisiana (which was consolidated with a prior suit filed by ILU) seeking a declaration that ILU must provide coverage to LaGen for the defense costs incurred in defending the U.S. DOJ lawsuit as well as indemnity costs.  LaGen and ILU both filed motions for summary judgment and on January 30, 2012, the court issued an order granting LaGen's motion finding that ILU had a duty to defend LaGen. On May 25, 2012, ILU filed a petition with the U.S. Court of Appeals for the Fifth Circuit seeking to appeal the trial court's summary judgment ruling. The Fifth Circuit heard oral argument on March 6, 2013. On May 15, 2013, the Fifth Circuit affirmed the district court's ruling that ILU has a duty to defend LaGen against the U.S. DOJ lawsuit. On May 29, 2013, ILU filed a petition for rehearing. The Fifth Circuit denied ILU's petition for rehearing on June 12, 2013. On October 2, 2013, LaGen filed a motion for summary judgment in the federal district court for the Middle District of Louisiana for recovery of LaGen's fees and costs related to the U.S. DOJ lawsuit, as well as its fees and costs related to the insurance coverage action.
	Big Cajun II Alleged Opacity Violations — On September 7, 2012, LaGen received a Consolidated Compliance Order & Notice of Potential Penalty, or CCO&NPP, from the LDEQ.  The CCO&NPP alleges there were opacity exceedance events from the Big Cajun II Power Plant on certain dates during the years 2007-2012.  On October 8, 2012, LaGen filed a Request for Administrative Adjudicatory hearing. LaGen and LDEQ have since reached an agreement in principle to resolve the matter for approximately $47,000. Following execution of a settlement agreement with LDEQ, notice of the settlement will be published for public comment, and is subject to approval by the Louisiana Attorney General within 90 days of the notice.
	Global Warming
	In February 2008, the Native Village of Kivalina and the City of Kivalina, Alaska filed a suit in the U.S. District Court for the Northern District of California against GenOn and 23 other electric generating and oil and gas companies. The lawsuit sought damages of up to $400 million for the cost of relocating the village allegedly because of global warming caused by the GHG emissions of the defendants. In late 2009, the District Court ordered that the case be dismissed and the plaintiffs appealed. In September 2012, the U.S. Court of Appeals for the Ninth Circuit dismissed plaintiffs' appeal. In October 2012, the plaintiffs petitioned for en banc rehearing of the case, which petition was denied in November 2012. In February 2013, plaintiffs filed a petition for certiorari with the U.S. Supreme Court seeking review of the decision of the U.S. Court of Appeals. In May 2013, the U.S. Supreme Court denied plaintiffs' petition, thereby ending the case.
	Actions Pursued by MC Asset Recovery
	With Mirant Corporation's emergence from bankruptcy protection in 2006, certain actions filed by GenOn Energy Holdings and some of its subsidiaries against third parties were transferred to MC Asset Recovery, a wholly owned subsidiary of GenOn Energy Holdings.  MC Asset Recovery is governed by a manager who is independent of NRG and GenOn.  MC Asset Recovery is a disregarded entity for income tax purposes.
	Under the remaining action transferred to MC Asset Recovery, MC Asset Recovery seeks to recover damages from Commerzbank AG and various other banks, or the Commerzbank Defendants, for alleged fraudulent transfers that occurred prior to GenOn Energy Holdings' bankruptcy proceedings.  In December 2010, the U.S. District Court for the Northern District of Texas dismissed MC Asset Recovery's complaint against the Commerzbank Defendants.  In January 2011, MC Asset Recovery appealed the District Court's dismissal of its complaint against the Commerzbank Defendants to the U.S. Court of Appeals for the Fifth Circuit.  In March 2012, the Court of Appeals reversed the District Court's dismissal and reinstated MC Asset Recovery's amended complaint against the Commerzbank Defendants.  If MC Asset Recovery succeeds in obtaining any recoveries from the Commerzbank Defendants, the Commerzbank Defendants have asserted that they will seek to file claims in GenOn Energy Holdings' bankruptcy proceedings for the amount of those recoveries.  GenOn Energy Holdings would vigorously contest the allowance of any such claims. If the Commerzbank Defendants were to receive an allowed claim as a result of a recovery by MC Asset Recovery on its claims against them, GenOn Energy Holdings would retain from the net amount recovered by MC Asset Recovery an amount equal to the dollar amount of the resulting allowed claim.
	Pending Natural Gas Litigation
	GenOn is party to five lawsuits, several of which are class action lawsuits, in state and federal courts in Kansas, Missouri, Nevada 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 antitrust 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 is 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. The Ninth Circuit reversed the decision of the U.S. District Court for the District of Nevada. On August 26, 2013, GenOn along with the other defendants in the lawsuit filed a petition for certiorari to the U.S. Supreme Court challenging the Ninth Circuit’s decision. In September 2012, the State of Nevada Supreme Court, which is handling the remaining case, affirmed dismissal by the Eighth Judicial District Court for Clark County, Nevada of all plaintiffs' claims against GenOn. In February 2013, the plaintiffs in the Nevada case filed a petition for certiorari to the U.S. Supreme Court. In June 2013, the U.S. Supreme Court denied the petition for certiorari, thereby ending one of the five lawsuits. GenOn has agreed to indemnify CenterPoint against certain losses relating to these lawsuits.
	New Source Review Matters
	The EPA and various states are investigating compliance of electric generating facilities with the pre-construction permitting requirements of the CAA known as “new source review.” Since 2000, the EPA has made information requests concerning several of the Company's subsidiaries' plants. The Company continues to correspond with the EPA regarding some of these requests. The EPA agreed to share information relating to its investigations with state environmental agencies. In 2005 and 2006, the Company received an NOV from the EPA alleging that past work at Big Cajun II violated regulations regarding new source review. Further discussion of this matter can be found in Note 15, Environmental Matters - South Central Region. In January 2009, the EPA issued an NOV alleging that past work at the Shawville, Portland and Keystone generating facilities violated regulations regarding new source review. In June 2011, the EPA issued an NOV alleging that past work at the Niles and Avon Lake generating facilities violated regulations regarding new source review. In April 2013, the Connecticut Department of Energy and Environmental Protection issued four NOVs alleging that past work at combustion turbines at three of the Company's Connecticut Jet Power facilities and Middletown facility violated regulations regarding new source review.
	In December 2007, the NJDEP sued GenOn in the U.S. District Court for the Eastern District of Pennsylvania, alleging that new source review violations occurred at the Portland generating facility. The suit sought installation of BACT for each pollutant, to enjoin GenOn from operating the generating facility if it is not in compliance with the CAA and civil penalties. The suit also named past owners of the plant as defendants, but the claims against the past owners were dismissed. In March 2009, the Connecticut Department of Energy and Environmental Protection became an intervening party to the suit. In July 2013, the court entered a Consent Decree which generally requires the cessation of coal combustion at Portland Units 1 and 2 and the payment of $1 million to benefit the environment in New Jersey and Connecticut. The entry of the Consent Decree resolved this matter.
	Cheswick Class Action Complaint
	In April 2012, a putative class action lawsuit was filed against GenOn in the Court of Common Pleas of Allegheny County, Pennsylvania alleging that emissions from the Cheswick generating facility have damaged the property of neighboring residents. The Company disputes these allegations. Plaintiffs have brought nuisance, negligence, trespass and strict liability claims seeking both damages and injunctive relief. Plaintiffs seek to certify a class that consists of people who own property or live within one mile of the Company's plant. In July 2012, the Company removed the lawsuit to the U.S. District Court for the Western District of Pennsylvania. In October 2012, the court granted the Company's motion to dismiss, which Plaintiffs appealed to the U.S. Court of Appeals for the Third Circuit. On August 20, 2013, the Third Circuit reversed the decision of the District Court. On September 3, 2013, the Company filed a petition for rehearing with the Third Circuit which was subsequently denied on September 23, 2013. On October 15, 2013, the Company filed a motion with the District Court seeking to stay the District Court case while it petitions for certiorari to the U.S. Supreme Court.
	Cheswick Monarch Mine NOV
	In 2008, the PADEP issued an NOV related to the Monarch mine located near the Cheswick generating facility. It has not been mined for many years. The Company uses it for disposal of low-volume wastewater from the Cheswick generating facility and for disposal of leachate collected from ash disposal facilities. The NOV addresses the alleged requirement to maintain a minimum pumping volume from the mine. The PADEP indicated it will seek a civil penalty of approximately $200,000. The Company contests the allegations in the NOV and has not agreed to such penalty. The Company is currently planning capital expenditures in connection with wastewater from Cheswick and leachate from ash disposal facilities.
	Ormond Beach Alleged Federal Clean Water Act Violations
	In October 2012, the Wishtoyo Foundation, a California-based cultural and environmental advocacy organization, through its Ventura Coastkeeper Program, filed suit in the U.S. District Court for the Central District of California regarding alleged violations of the CWA associated with discharges of stormwater from the Ormond Beach generating facility. The Wishtoyo Foundation alleged that elevated concentrations of pollutants in stormwater discharged from the Ormond Beach generating facility were affecting adjacent aquatic resources in violation of (i) the Statewide General Industrial Stormwater permit (a general National Pollution Discharge Elimination System permit issued by the California State Water Resources Control Board that authorizes stormwater discharges from industrial facilities in California) and (ii) the state's Porter-Cologne Water Quality Control Act. The Wishtoyo Foundation further alleged that the Company had not implemented effective stormwater control and treatment measures and that the Company had not complied with the sampling and reporting requirements of the General Industrial Stormwater permit. The Company settled this matter in May 2013 and agreed to make operational changes and pay $79,000 in legal fees, $65,000 for supplemental environmental projects, and $15,000 for monitoring costs.
	Maryland Fly Ash Facilities
	The Company has three fly ash facilities in Maryland: Faulkner, Westland and Brandywine. Fly ash from the Morgantown and Chalk Point generating facilities is disposed of at Brandywine. Fly ash from the Dickerson generating facility is disposed of at Westland. Fly ash is no longer disposed of at the Faulkner facility. As described below, the MDE had sued NRG MD Ash Management and GenOn Mid-Atlantic regarding Faulkner, Brandywine and Westland. The MDE also had threatened not to renew the water discharge permits for all three facilities.
	Faulkner Litigation — In May 2008, the MDE sued GenOn MidAtlantic and NRG MD Ash Management in the Circuit Court for Charles County, Maryland alleging violations of Maryland's water pollution laws at Faulkner. The MDE contended that the operation of Faulkner had resulted in the discharge of pollutants that exceeded Maryland's water quality criteria and without the appropriate NPDES permit. The MDE also alleged that GenOn failed to perform certain sampling and reporting required under an applicable NPDES permit. The MDE complaint requested that the court (i) prohibit continuation of the alleged unpermitted discharges, (ii) require GenOn to cease from further disposal of any coal combustion byproducts at Faulkner and close and cap the existing disposal cells and (iii) assess civil penalties. In July 2008, GenOn filed a motion to dismiss the complaint, arguing that the discharges are permitted by a December 2000 Consent Order. In January 2011, the MDE dismissed without prejudice its complaint and informed GenOn that it intended to file a similar lawsuit in federal court. In May 2011, the MDE filed a complaint against GenOn Mid-Atlantic and NRG MD Ash Management in the U.S. District Court for the District of Maryland alleging violations at Faulkner of the Clean Water Act and Maryland's Water Pollution Control Law. The MDE contends that (i) certain of GenOn's water discharges are not authorized by the existing permit and (ii) operation of the Faulkner facility has resulted in discharges of pollutants that violate water quality criteria. The complaint asked the court to, among other things, (i) enjoin further disposal of coal ash; (ii) enjoin discharges that are not authorized by the existing permit; (iii) require numerous technical studies; (iv) impose civil penalties and (v) award MDE attorneys' fees. The Company disputed these allegations.
	Brandywine Litigation — In April 2010, the MDE filed a complaint against GenOn MidAtlantic and NRG MD Ash Management in the U.S. District Court for the District of Maryland asserting violations at Brandywine of the CWA and Maryland's Water Pollution Control Law. The MDE contended that the operation of Brandywine has resulted in discharges of pollutants that violate Maryland's water quality criteria. The complaint requested that the court, among other things, (i) enjoin further disposal of coal combustion waste at Brandywine, (ii) require the existing open disposal cells to be closed and capped within one year, (iii) impose civil penalties and (iv) award MDE attorneys' fees. In September 2010, four environmental advocacy groups became intervening parties in the proceeding.
	Westland Litigation — In January 2011, the MDE informed GenOn that it intended to sue for alleged violations at Westland of Maryland's water pollution laws, which suit was filed in U.S. District Court for the District of Maryland in December 2012.
	Permit Renewals — In March 2011, the MDE tentatively determined to deny NRG MD Ash Management's application for the renewal of the water discharge permit for Brandywine, which could have resulted in a significant increase in operating expenses for the GenOn Mid Atlantic's Chalk Point and Morgantown generating facilities. The MDE also had indicated that it was planning to deny the Company's applications for the renewal of the water discharge permits for Faulkner and Westland. Denial of the renewal of the water discharge permit for the latter facility could have resulted in a significant increase in operating expenses for the Dickerson generating facility.
	Settlement — In April 2013, NRG MD Ash Management and MDE signed a Consent Decree settling the disputes at each of the three ash facilities. GenOn agreed to pay a civil penalty of $1.9 million for alleged past violations and an additional $0.6 million (for agreed prospective penalties while the settlement is implemented). GenOn agreed to develop a technical solution, which includes installing synthetic caps on the closed cells of each of the three ash facilities, for which $47 million has been reserved, and to remediate the site. At this time, the Company cannot reasonably estimate the upper range of its obligation for remediating the sites because the Company has not: (i) finished assessing each site including identifying the full impacts to both ground and surface water and the impacts to the surrounding habitat; (ii) finalized with the MDE the standards to which it must remediate; and (iii) identified the technologies required, if any, to meet the yet to be determined remediation standards at each site nor the timing of the design and installation of such technologies.
	Energy Plus Holdings Purported Class Actions
	Energy Plus Holdings was sued in six purported class action lawsuits, two in New York, two in New Jersey, and two in Pennsylvania. On February 28, 2013, Energy Plus Holdings entered into a settlement agreement with plaintiffs to resolve all of the claims in the six pending suits, subject to court approval.  On September 17, 2013, the U.S. District Court, for the Southern District of New York entered an order approving the settlement. This settlement became final and nonappealable on October 27, 2013. Energy Plus Holdings continues to cooperate with the Connecticut Office of Attorney General and Office of Consumer Counsel and the State of New York Office of Attorney General to resolve certain issues related to Energy Plus Holdings's sales, marketing and business practices.  Energy Plus Holdings and the Connecticut Office of Attorney General and Office of Consumer Counsel have been involved in settlement discussions and their efforts to reach a resolution continue.
	Purported Class Actions related to July 22, 2012 Announcement of NRG/GenOn Merger Agreement
	NRG was named as a defendant in eight purported class actions in Texas and Delaware related to its announcement of its agreement to acquire all outstanding shares of GenOn. These cases were consolidated into one state court case in each of Delaware and Texas and a federal court case in Texas. The plaintiffs generally alleged breach of fiduciary duties, as well as conspiracy, aiding and abetting breaches of fiduciary duties. Plaintiffs generally sought to: be certified as a class; enjoin the merger; direct the defendants to exercise their fiduciary duties; rescind the acquisition; and be awarded attorneys' fees costs and other relief that the court deems appropriate. Plaintiffs also demanded that there be additional disclosures regarding the merger terms. On October 24, 2012, the parties to the Delaware state court case executed a Memorandum of Understanding to resolve the Delaware purported class action lawsuit. In March 2013, the parties finalized the settlement of the Delaware action. On June 3, 2013, the court approved the Delaware class action settlement thereby ending the Delaware lawsuit. The remaining Texas state and federal court cases were dismissed in July 2013 and August 2013, respectively, thereby ending these matters.
	Maryland Department of the Environment v. GenOn Chalk Point and GenOn Mid-Atlantic
	On January 25, 2013, Food & Water Watch, the Patuxent Riverkeeper and the Potomac Riverkeeper (together, the Citizens Group) sent NRG a letter alleging that the Chalk Point, Dickerson and Morgantown generating facilities were violating the terms of the three National Pollution Discharge Elimination System permits by discharging nitrogen and phosphorous in excess of the limits in each permit. On March 21, 2013, the MDE sent the Company a similar letter with respect to the Chalk Point and Dickerson facilities, threatening to sue within 60 days if the Company did not bring itself into compliance. On June 11, 2013, the Maryland Attorney General on behalf of the MDE filed a complaint in the U.S. District Court for the District of Maryland alleging violations of the Clean Water Act and Maryland environmental laws related to water. The lawsuit seeks injunctive relief and civil penalties in excess of $100,000.
	Huntley Power LLC Subpoena
	Huntley Power LLC was served with a subpoena on May 13, 2013 from the U.S. Department of Justice requesting information regarding the plant's use and handling of diesel fuel. The Company is cooperating with the U.S Department of Justice to address the issues related to the use and handling of diesel fuel.
	Texas Franchise Audit
	During the second quarter of 2013, the Company settled the Texas Franchise tax dispute with the state relating to years 2001 through 2007. Prior to the GenOn acquisition, the State of Texas issued franchise tax assessments against GenOn as a result of its audit indicating an underpayment of franchise tax of $72 million (including interest and penalties through June 30, 2013 of $29 million). These assessments relate primarily to a claim by Texas that would change the sourcing of intercompany receipts thereby increasing the amount of tax due. GenOn disagreed with most of the State's assessment and its determination and had accordingly accrued a portion of the liability but had protested the entire assessment.  In June 2013, the Company settled the matter with the State by agreeing to pay $11 million on issues arising from the audit, and reversed the remainder of the accrual. The reversal was recorded as a measurement period adjustment to the amounts recognized on the acquisition date.

Regulatory_Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2013
Regulatory Matters Disclosure [Abstract]	'
Regulatory Matters	'
	Regulatory Matters
	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 a party 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.
	East Region
	Reliability Must Run Agreements for Elrama and Niles — In May 2012, GenOn filed with FERC an RMR rate schedule governing operation of unit 4 of the Elrama generating facility and unit 1 of the Niles generating facility.  PJM determined that each of these units was needed past its planned deactivation date of June 1, 2012 to maintain transmission system reliability on the PJM system pending the completion of transmission upgrades.  The RMR rate schedule sets forth the terms, conditions and cost-based rates under which GenOn operated the units for reliability purposes through September 30, 2012, the date PJM indicated the units would no longer be needed for reliability.  In July 2012, FERC accepted GenOn's RMR rate schedule subject to hearing and settlement procedures.  In the settlement discussions ordered by FERC, or in any subsequent hearing, the Company's RMR rate schedule may be modified from that which was filed.  The rates GenOn charged are subject to refund pending a ruling or settlement. The Company filed a settlement of all outstanding issues in May 2013, which several parties are contesting. The matter is pending before FERC.
	Retail
	MISO SECA — Green Mountain Energy previously provided competitive retail energy supply in the MISO region during the relevant period of January 1, 2002, to December 31, 2005.  By order dated November 18, 2004, FERC eliminated certain regional through-and-out transmission rates charged by transmission owners in MISO and PJM. In order to temporarily compensate the transmission owners for lost revenues, FERC ordered MISO, PJM and their respective transmission owners to revamp the way that ISOs manage certain cross-system congestion costs, known as Seams Elimination Charge/Cost Adjustments/Assignments, or SECA, charges effective December 1, 2004, through March 31, 2006.  The tariff amendments filed by MISO and the MISO transmission owners allocated certain SECA charges to various zones and sub-zones within MISO, including a sub-zone called the Green Mountain Energy Company Sub-zone.  During several years of extensive litigation before FERC, several transmission owners sought to recover SECA charges from Green Mountain Energy. Green Mountain Energy denied responsibility for any SECA charges and did not pay any asserted SECA charges.
	On May 21, 2010, FERC issued two orders, including its Order on Initial Decision, in which FERC determined that approximately $22 million plus interest of SECA charges were owed not by Green Mountain Energy but rather by BP Energy - one of Green Mountain Energy's suppliers during the period at issue.  On August 19, 2010, the transmission owners and MISO made compliance filings in accordance with FERC's Orders allocating SECA charges to a BP Energy Sub-zone, and making no allocation to a Green Mountain Energy sub-zone.  FERC has not yet ruled on those compliance filings.
	On September 30, 2011, FERC issued orders denying all requests for rehearing and again determined that SECA charges were not owed by Green Mountain Energy.  Numerous parties, including BP Energy, sought judicial review of FERC's orders, and Green Mountain Energy was granted intervenor status in the consolidated appeals. Most appellants subsequently settled with the transmission owners and withdrew their appeals, including BP Energy, which agreed to pay approximately $24 million to the three transmission owners signing the agreement, with another $1 million offered to the remaining PJM transmission owners, should they choose to join the settlement; all chose to do so. FERC approved the settlement, and BP Energy moved to dismiss its appeals; its motions to dismiss were granted by the Court.
	West Region
	California Station Power — On December 18, 2012, in Calpine Corporation v. FERC, the U.S. Court of Appeals for the D.C. Circuit upheld a decision by FERC disclaiming jurisdiction over how the states impose retail station power charges. The CPUC may now establish retail charges for future station power consumption. Due to reservation-of-rights language in the California utilities' state-jurisdictional station power tariffs, the court's ruling arguably requires California generators to pay state-imposed retail charges back to the date of enrollment by the facilities in the CAISO's station period program (February 1, 2009, for the Company's Encina and El Segundo facilities; March 1, 2009, for the Company's Long Beach facility).
	On November 18, 2011, Southern California Edison Company filed with the CPUC, seeking authorization to begin charging generators station power charges, and to assess such charges retroactively, which the Company and other generators have challenged. On August 13, 2012, the CPUC Energy Division issued a draft resolution in which it rejected the Company's arguments and approved Southern California Edison's proposed station power charges, including retroactive implementation, but proposing a credit to generators for some portion of their retail station power bill. However, the CPUC withdrew the draft resolution from the calendar and consideration of the measure has not yet been rescheduled. The Company believes it has established an appropriate reserve.

Environmental_Matters

Environmental Matters	9 Months Ended
	Sep. 30, 2013
Environmental Matters Disclosure [Abstract]	'
Environmental Matters	'
	Environmental Matters
	NRG is subject to a wide range of environmental regulations in the development, ownership, construction and operation of projects in the United States and Australia. These laws and regulations generally require that governmental permits and approvals be obtained before construction and during operation of power plants. Environmental regulations have become increasingly stringent and NRG expects this trend to continue. The electric generation industry is likely to face new requirements to address various emissions, including greenhouse gases, as well as combustion byproducts, water discharge and use, and threatened and endangered species. In general, future laws and regulations 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 operations.
	The EPA released CSAPR on July 7, 2011, which was scheduled to replace CAIR on January 1, 2012. On August 21, 2012, the U.S. Court of Appeals for the D.C. Circuit issued an opinion vacating CSAPR and keeping CAIR in place until the EPA can replace it. The EPA petitioned the Supreme Court seeking review of this decision, which petition was granted. The Supreme Court will hear oral argument in the case on December 10, 2013. The Court of Appeals decision was beneficial to the Company as it eliminated an SO2 allowance reduction which was to have occurred before the MATS compliance date. While NRG is unable to predict the final outcome of the ongoing litigation, the Company's investment in pollution controls and cleaner technologies coupled with planned strategic plant retirements leaves the fleet well positioned for compliance.
	Environmental Capital Expenditures
	Based on current rules, technology and preliminary plans based on some proposed rules, NRG estimates that environmental capital expenditures from 2013 through 2017 required to comply with environmental laws will be approximately $530 million which includes $223 million for GenOn. These costs are primarily associated with (i) controls to satisfy MATS and the recent NSR settlement at Big Cajun II; (ii) controls to satisfy MATS at W.A. Parish, Limestone and Conemaugh; and (iii) NOx controls for Sayreville and Gilbert. The decrease from NRG's estimate disclosed in the Company's 2012 Form 10‑K is related to changes in technology related to complying with MATS and the NSR settlement at Big Cajun II, and the selection of more cost-effective environmental compliance solutions at Cheswick. NRG continues to explore cost-effective compliance alternatives to further reduce costs.
	NRG's contracts with its rural electric cooperative customers in the South Central region allow for recovery of a portion of the region's environmental capital costs incurred as the result of complying with any change in environmental law. Cost recoveries begin once the environmental equipment becomes operational and include a return on capital. The actual recoveries will depend, among other things, on the timing of the completion of the capital projects and the remaining duration of the contracts.
	East Region
	The EPA and various states are investigating compliance of electric generating facilities with the pre-construction permitting requirements of the CAA known as “new source review,” or NSR. In January 2009, GenOn received an NOV from the EPA alleging that past work at Keystone, Portland and Shawville generating facilities violated regulations regarding NSR. In June 2011, GenOn received an NOV from the EPA alleging that past work at Avon Lake and Niles generating stations violated NSR. In December 2007, the NJDEP filed suit alleging that NSR violations occurred at the Portland generating station, which suit was resolved pursuant to a July 2013 Consent Decree. The Shawville, Niles and Portland generating units that are the subject of the NOVs are scheduled for retirement soon. 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 violated regulations regarding NSR.
	In 2008, the PADEP issued an NOV related to the inactive Monarch mine where low-volume wastewater from the Cheswick Generating Station and ash leachate was historically disposed. Resolution of the NOV could result in operational requirements such as pumping a minimum volume of water from the mine and a penalty of approximately $200,000.
	In January 2006, NRG's Indian River Operations, Inc. was notified that it may be a potentially responsible party with respect to Burton Island Old Ash Landfill, a historic captive landfill located at the Indian River facility. On October 1, 2007, NRG signed an agreement with DNREC to investigate the site through the Voluntary Clean-up Program. On February 4, 2008, DNREC issued findings that no further action is required in relation to surface water and that a previously planned shoreline stabilization project would satisfactorily address shoreline erosion. The landfill itself required a Remedial Investigation and Feasibility Study to determine the type and scope of any additional required work. The DNREC approved the Feasibility Study in December 2012. In January 2013, DNREC proposed a remediation plan based on the Feasibility Study. The remediation plan was approved in October 2013. The cost of completing the work required by the approved remediation plan is consistent with amounts previously budgeted. On May 29, 2008, DNREC requested that NRG's Indian River Operations, Inc. participate in the development and performance of a Natural Resource Damage Assessment at the Burton Island Old Ash Landfill. NRG is currently working with DNREC and other trustees to close out the assessment process.
	The MDE sued GenOn for alleged violations of water pollution laws at three fly ash disposal sites in Maryland: Faulkner (2008/2011), Brandywine (2010) and Westland (2012). On April 30, 2013, the court approved the consent decree resolving these issues. GenOn has discontinued use of the Faulkner disposal site and opened a new, state of the art carbon burnout facility at its Morgantown plant that allows greater beneficial reuse (as a cement substitute).
	For further discussion of these matters, refer to Note 13, Commitments and Contingencies.
	South Central Region
	In 2009, the U.S. DOJ, on behalf of the EPA, and later the Louisiana Department of Environmental Quality on behalf of the state of Louisiana, sued LaGen in federal district court in the Middle District of Louisiana alleging violations of the CAA at the Big Cajun II power plant. On March 6, 2013, the court entered a Consent Decree resolving the matter. In addition to a fine of $3.5 million and mitigation projects totaling $10.5 million, the Consent Decree includes: (i) annual emission caps for NOx and SO2; (ii) installation of selective non-catalytic reduction on Units 1, 2 and 3 by May 1, 2014; (iii) installation of dry sorbent injection on Unit 1 by April 15, 2015 followed by a further reduction in SO2 in March 2025; (iv) conversion of Unit 2 to natural gas; and (v) surrender of any excess allowances associated with the NRG owned portion of the plant. For further discussion of this matter, refer to Note 13, Commitments and Contingencies.

Condensed_Consolidating_Financ

Condensed Consolidating Financial Information	9 Months Ended
	Sep. 30, 2013
Condensed Consolidating Financial Information Disclosure [Abstract]	'
Condensed Consolidating Financial Information	'
	Condensed Consolidating Financial Information
	As of September 30, 2013, the Company had outstanding $5.7 billion of Senior Notes due from 2018 - 2023, as shown in Note 7, 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, including GenOn and its subsidiaries.
	Unless otherwise noted below, each of the following guarantor subsidiaries fully and unconditionally guaranteed the Senior Notes as of September 30, 2013:
	Ace Energy, Inc.	Middletown Power LLC	NRG Oswego Harbor Power Operations, Inc.
	Allied Warranty LLC	Montville Power LLC	NRG PacGen Inc.
	Arthur Kill Power LLC	NEO Corporation	NRG Power Marketing LLC
	Astoria Gas Turbine Power LLC	NEO Freehold-Gen LLC	NRG Reliability Solutions LLC
	Bidurenergy, Inc.	NEO Power Services Inc.	NRG Renter's Protection LLC
	Cabrillo Power I LLC	New Genco GP, LLC	NRG Retail LLC
	Cabrillo Power II LLC	Norwalk Power LLC	NRG Rockford Acquisition LLC
	Carbon Management Solutions LLC	NRG Affiliate Services Inc.	NRG Saguaro Operations Inc.
	Clean Edge Energy LLC	NRG Artesian Energy LLC	NRG Security LLC
	Conemaugh Power LLC	NRG Arthur Kill Operations Inc.	NRG Services Corporation
	Connecticut Jet Power LLC	NRG Astoria Gas Turbine Operations Inc.	NRG SimplySmart Solutions LLC
	Cottonwood Development LLC	NRG Bayou Cove LLC	NRG South Central Affiliate Services Inc.
	Cottonwood Energy Company LP	NRG Cabrillo Power Operations Inc.	NRG South Central Generating LLC
	Cottonwood Generating Partners I LLC	NRG California Peaker Operations LLC	NRG South Central Operations Inc.
	Cottonwood Generating Partners II LLC	NRG Cedar Bayou Development Company, LLC	NRG South Texas LP
	Cottonwood Generating Partners III LLC	NRG Connecticut Affiliate Services Inc.	NRG Texas C&I Supply LLC
	Cottonwood Technology Partners LP	NRG Construction LLC	NRG Texas Gregory LLC
	Devon Power LLC	NRG Curtailment Solutions LLC	NRG Texas Holding Inc.
	Dunkirk Power LLC	NRG Development Company Inc.	NRG Texas LLC
	Eastern Sierra Energy Company LLC	NRG Devon Operations Inc.	NRG Texas Power LLC
	El Segundo Power, LLC	NRG Dispatch Services LLC	NRG Unemployment Protection LLC
	El Segundo Power II LLC	NRG Dunkirk Operations Inc.	NRG Warranty Services LLC
	Elbow Creek Wind Project LLC	NRG El Segundo Operations Inc.	NRG West Coast LLC
	Energy Alternatives Wholesale, LLC	NRG Energy Labor Services LLC	NRG Western Affiliate Services Inc.
	Energy Curtailment Specialists, Inc.	NRG Energy Services Group LLC	O'Brien Cogeneration, Inc. II
	Energy Plus Holdings LLC	NRG Energy Services LLC	ONSITE Energy, Inc.
	Energy Plus Natural Gas LLC	NRG Generation Holdings, Inc.	Oswego Harbor Power LLC
	Energy Protection Insurance Company	NRG Home & Business Solutions LLC	RE Retail Receivables, LLC
	Everything Energy 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
	Green Mountain Energy Company	NRG Huntley Operations Inc.	Reliant Energy Retail Services, LLC
	(NY Com) LLC	NRG Identity Protect LLC	RERH Holdings, LLC
	Green Mountain Energy Company	NRG Ilion Limited Partnership	Saguaro Power LLC
	(NY Res) LLC	NRG Ilion LP LLC	Somerset Operations Inc.
	Gregory Partners, LLC	NRG International LLC	Somerset Power LLC
	Gregory Power Partners LLC	NRG Maintenance Services LLC	Texas Genco Financing Corp.
	Huntley Power LLC	NRG Mextrans Inc.	Texas Genco GP, LLC
	Independence Energy Alliance LLC	NRG MidAtlantic Affiliate Services Inc.	Texas Genco Holdings, Inc.
	Independence Energy Group LLC	NRG Middletown Operations Inc.	Texas Genco LP, LLC
	Independence Energy Natural Gas LLC	NRG Montville Operations Inc.	Texas Genco Operating Services, LLC
	Indian River Operations Inc.	NRG New Jersey Energy Sales LLC	Texas Genco Services, LP
	Indian River Power LLC	NRG New Roads Holdings LLC	US Retailers LLC
	Keystone Power LLC	NRG North Central Operations Inc.	Vienna Operations Inc.
	Langford Wind Power, LLC	NRG Northeast Affiliate Services Inc.	Vienna Power LLC
	Lone Star A/C & Appliance Repair, LLC	NRG Norwalk Harbor Operations Inc.	WCP (Generation) Holdings LLC
	Louisiana Generating LLC	NRG Operating Services, Inc.	West Coast Power LLC
	Meriden Gas Turbines 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. Except for NRG Bayou Cove, LLC, which is subject to certain restrictions under the Company's Peaker financing agreements, there are no restrictions on the ability of any of the guarantor subsidiaries to transfer funds to NRG. In addition, 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 Securities and Exchange Commission's 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, 2013
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Operating Revenues
	Total operating revenues	$	2,464		$	1,019		$	—		$	7		$	3,490
Operating Costs and Expenses
Cost of operations	1,792			566			(6		)	3			2,355
Depreciation and amortization	213			102			3			—			318
Selling, general and administrative	116			70			39			4			229
Acquisition-related transaction and integration costs	—			13			13			—			26
Development activity expenses	—			14			13			—			27
Total operating costs and expenses	2,121			765			62			7			2,955
Operating Income/(Loss)	343			254			(62		)	—			535
Other Income/(Expense)
Equity in (loss)/earnings of consolidated subsidiaries	(25		)	(5		)	309			(279		)	—
Equity in (loss)/earnings of unconsolidated affiliates	(10		)	10			—			(5		)	(5		)
Other income, net	5			3			1			(4		)	5
Loss on debt extinguishment	—			(1		)	—			—			(1		)
Interest expense	(3		)	(88		)	(137		)	—			(228		)
Total other (expense)/income	(33		)	(81		)	173			(288		)	(229		)
Income Before Income Taxes	310			173			111			(288		)	306
Income tax expense/(benefit)	126			59			(22		)	—			163
Net Income	184			114			133			(288		)	143
Less: Net income attributable to noncontrolling interest	—			32			9			(22		)	19
Net Income attributable to	$	184		$	82		$	124		$	(266	)	$	124
NRG Energy, Inc.
(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, 2013
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Operating Revenues
Total operating revenues	$	6,225		$	2,394		$	—		$	(119	)	$	8,500
Operating Costs and Expenses
Cost of operations	4,697			1,593			1			(112		)	6,179
Depreciation and amortization	624			288			9			—			921
Selling, general and administrative	341			173			164			(7		)	671
Acquisition-related transaction and integration costs	—			54			41			—			95
Development activity expenses	—			24			39			—			63
Total operating costs and expenses	5,662			2,132			254			(119		)	7,929
Operating Income/(Loss)	563			262			(254		)	—			571
Other Income/(Expense)
Equity in (loss)/earnings of consolidated subsidiaries	(4		)	(9		)	363			(350		)	—
Equity in (loss)/earnings of unconsolidated affiliates	(8		)	16			—			(2		)	6
Other income, net	7			5			3			(6		)	9
Loss on debt extinguishment	—			(12		)	(38		)	—			(50		)
Interest expense	(13		)	(229		)	(388		)	—			(630		)
Total other expense	(18		)	(229		)	(60		)	(358		)	(665		)
Income/(Loss) Before Income Taxes	545			33			(314		)	(358		)	(94		)
Income tax expense/(benefit)	212			(10		)	(249		)	—			(47		)
Net Income/(Loss)	333			43			(65		)	(358		)	(47		)
Less: Net income attributable to noncontrolling interest	—			40			9			(22		)	27
Net Income/(Loss) attributable to	$	333		$	3		$	(74	)	$	(336	)	$	(74	)
NRG Energy, Inc.
(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, 2013
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Net Income	$	184		$	114		$	133		$	(288	)	$	143
Other comprehensive (loss)/income, net of tax
Unrealized (loss)/gain on derivatives, net	(13		)	(8		)	17			(12		)	(16		)
Foreign currency translation adjustments, net	—			4			1			—			5
Other comprehensive (loss)/income	(13		)	(4		)	18			(12		)	(11		)
Comprehensive income	171			110			151			(300		)	132
Less: Comprehensive income attributable to noncontrolling interest	—			29			9			(20		)	18
Comprehensive income attributable to NRG Energy, Inc.	171			81			142			(280		)	114
Dividends for preferred shares	—			—			2			—			2
Comprehensive income available for common stockholders	$	171		$	81		$	140		$	(280	)	$	112
(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, 2013
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Net Income/(Loss)	$	333		$	43		$	(65	)	$	(358	)	$	(47	)
Other comprehensive (loss)/income, net of tax
Unrealized (loss)/gain on derivatives, net	(54		)	41			9			12			8
Foreign currency translation adjustments, net	—			(11		)	(3		)	—			(14		)
Available-for-sale securities, net	—			—			2			—			2
Defined benefit plan, net	—			25			—			—			25
Other comprehensive (loss)/income	(54		)	55			8			12			21
Comprehensive income/(loss)	279			98			(57		)	(346		)	(26		)
Less: Comprehensive income attributable to noncontrolling interest	—			39			9			(22		)	26
Comprehensive income/(loss) attributable to NRG Energy, Inc.	279			59			(66		)	(324		)	(52		)
Dividends for preferred shares	—			—			7			—			7
Comprehensive income/(loss) available for common stockholders	$	279		$	59		$	(73	)	$	(324	)	$	(59	)
(a)	All significant intercompany transactions have been eliminated in consolidation.
NRG ENERGY, INC. AND SUBSIDIARIES
CONDENSED CONSOLIDATING BALANCE SHEETS
September 30, 2013
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
ASSETS	(In millions)
Current Assets
Cash and cash equivalents	$	23		$	1,110		$	996		$	—		$	2,129
Funds deposited by counterparties	—			122			—			—			122
Restricted cash	18			278			11			—			307
Accounts receivable, net	1,132			234			—			—			1,366
Inventory	406			455			—			—			861
Derivative instruments	914			491			—			(16		)	1,389
Cash collateral paid in support of energy risk management activities	253			35			—			—			288
Renewable energy grant receivable	—			344			1			—			345
Prepayments and other current assets	4,103			283			(3,414		)	(530		)	442
Total current assets	6,849			3,352			(2,406		)	(546		)	7,249
Net property, plant and equipment	9,651			10,822			149			(22		)	20,600
Other Assets
Investment in subsidiaries	108			(108		)	18,218			(18,218		)	—
Equity investments in affiliates	18			724			10			(126		)	626
Notes receivable, less current portion	—			66			255			(245		)	76
Goodwill	1,941			12			—			—			1,953
Intangible assets, net	988			172			33			(52		)	1,141
Nuclear decommissioning trust fund	524			—			—			—			524
Deferred income tax	—			784			715			—			1,499
Derivative instruments	202			307			—			(3		)	506
Other non-current assets	80			239			370			—			689
Total other assets	3,861			2,196			19,601			(18,644		)	7,014
Total Assets	$	20,361		$	16,370		$	17,344		$	(19,212	)	$	34,863
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities
Current portion of long-term debt and capital leases	$	1		$	890		$	20		$	—		$	911
Accounts payable	678			436			26			—			1,140
Accounts payable — affiliate	6			1,973			(1,572		)	(407		)	—
Derivative instruments	887			193			—			(16		)	1,064
Deferred income taxes	369			(264		)	7			—			112
Cash collateral received in support of energy risk management activities	—			122			—			—			122
Accrued expenses and other current liabilities	283			478			272			—			1,033
Total current liabilities	2,224			3,828			(1,247		)	(423		)	4,382
Other Liabilities
Long-term debt and capital leases	316			7,965			7,766			(245		)	15,802
Nuclear decommissioning reserve	290			—			—			—			290
Nuclear decommissioning trust liability	303			—			—			—			303
Deferred income taxes	886			(836		)	—			—			50
Derivative instruments	279			96			—			(3		)	372
Out-of-market contracts	162			1,026			—			(31		)	1,157
Other non-current liabilities	510			631			236			—			1,377
Total non-current liabilities	2,746			8,882			8,002			(279		)	19,351
Total liabilities	4,970			12,710			6,755			(702		)	23,733
3.625% convertible perpetual preferred stock	—			—			249			—			249
Stockholders’ Equity	15,391			3,660			10,340			(18,510		)	10,881
Total Liabilities and Stockholders’ Equity	$	20,361		$	16,370		$	17,344		$	(19,212	)	$	34,863
(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, 2013
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Cash Flows from Operating Activities
Net Cash Provided/(Used) by Operating Activities	1,334			135			(1,800		)	1,154			823
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	(1,158		)	4			1,154			—			—
Acquisition of businesses, net of cash acquired	—			(59		)	(315		)	—			(374		)
Capital expenditures	(154		)	(1,388		)	(39		)	—			(1,581		)
(Increase)/decrease in restricted cash, net	(7		)	(61		)	1			—			(67		)
Increase in restricted cash — U.S. DOE projects	—			(18		)	(2		)	—			(20		)
Decrease/(increase) in notes receivable	2			(16		)	(8		)	—			(22		)
Investments in nuclear decommissioning trust fund securities	(369		)	—			—			—			(369		)
Proceeds from sales of nuclear decommissioning trust fund securities	344			—			—			—			344
Proceeds from renewable energy grants	—			52			—			—			52
Proceeds from sale of assets, net of cash disposed of	13			—			—			—			13
Other	7			(1		)	(13		)	—			(7		)
Net Cash (Used)/Provided by Investing Activities	(1,322		)	(1,487		)	778			—			(2,031		)
Cash Flows from Financing Activities
Proceeds from intercompany loans	—			—			1,154			(1,154		)	—
Payment of dividends to common and preferred stockholders	—			—			(113		)	—			(113		)
Payment for treasury stock	—			—			(25		)	—			(25		)
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	(67		)	244			—			—			177
Contributions from noncontrolling interest in subsidiaries	—			504			—			—			504
Proceeds from issuance of long-term debt	—			1,120			485			—			1,605
Proceeds from issuance of common stock	—			—			14			—			14
Payment of debt issuance and hedging costs	—			(9		)	(34		)	—			(43		)
Payments for short and long-term debt	—			(654		)	(214		)	—			(868		)
Net Cash (Used)/Provided by Financing Activities	(67		)	1,205			1,267			(1,154		)	1,251
Effect of exchange rate changes on cash and cash equivalents	—			(1		)	—			—			(1		)
Net (Decrease)/Increase in Cash and Cash Equivalents	(55		)	(148		)	245			—			42
Cash and Cash Equivalents at Beginning of Period	78			1,258			751			—			2,087
Cash and Cash Equivalents at End of Period	$	23		$	1,110		$	996		$	—		$	2,129
(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, 2012
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Operating Revenues
Total operating revenues	$	2,237		$	120		$	—		$	(26	)	$	2,331
Operating Costs and Expenses
Cost of operations	1,715			47			1			(23		)	1,740
Depreciation and amortization	217			20			2			—			239
Selling, general and administrative	154			—			73			(3		)	224
Acquisition-related transaction and integration costs	—			—			18			—			18
Development activity expenses	—			14			10			—			24
Total operating costs and expenses	2,086			81			104			(26		)	2,245
Operating Income/(Loss)	151			39			(104		)	—			86
Other Income/(Expense)
Equity in (losses)/earnings of consolidated subsidiaries	(10		)	1			121			(112		)	—
Equity in earnings of unconsolidated affiliates	4			—			—			—			4
Other income, net	—			2			7			—			9
Loss on debt extinguishment	—			—			(41		)	—			(41		)
Interest expense	(5		)	(21		)	(137		)	—			(163		)
Total other expense	(11		)	(18		)	(50		)	(112		)	(191		)
Income/(Loss) Before Income Taxes	140			21			(154		)	(112		)	(105		)
Income tax expense/(benefit)	67			(27		)	(153		)	—			(113		)
Net Income/(Loss)	73			48			(1		)	(112		)	8
Less: Net income attributable to noncontrolling interest	—			9			—			—			9
Net Income/(Loss) attributable to NRG Energy, Inc.	$	73		$	39		$	(1	)	$	(112	)	$	(1	)
(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, 2012
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Operating Revenues
Total operating revenues	$	6,058		$	353		$	—		$	(52	)	$	6,359
Operating Costs and Expenses
Cost of operations	4,512			186			7			(45		)	4,660
Depreciation and amortization	647			48			8			—			703
Selling, general and administrative	387			6			227			(7		)	613
Acquisition-related transaction and integration costs	—			—			18			—			18
Development activity expenses	—			22			30			—			52
Total operating costs and expenses	5,546			262			290			(52		)	6,046
Operating Income/(Loss)	512			91			(290		)	—			313
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	6			(11		)	463			(458		)	—
Equity in earnings of unconsolidated affiliates	6			20			—			—			26
Other income, net	—			4			8			—			12
Loss on debt extinguishment	—			—			(41		)	—			(41		)
Interest expense	(21		)	(60		)	(414		)	—			(495		)
Total other (expense)/income	(9		)	(47		)	16			(458		)	(498		)
Income/(Loss) Before Income Taxes	503			44			(274		)	(458		)	(185		)
Income tax expense/(benefit)	193			(122		)	(317		)	—			(246		)
Net Income	310			166			43			(458		)	61
Less: Net income attributable to noncontrolling interest	—			18			—			—			18
Net Income attributable to NRG Energy, Inc.	$	310		$	148		$	43		$	(458	)	$	43
(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, 2012
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Net Income/(Loss)	$	73		$	48		$	(1	)	$	(112	)	$	8
Other comprehensive loss, net of tax
Unrealized loss on derivatives, net	(43		)	(14		)	(54		)	68			(43		)
Foreign currency translation adjustments, net	—			—			1			—			1
Foreign currency translation realized upon sale of Schkopau	—			(11		)	—			—			(11		)
Available-for-sale securities, net	—			—			2			—			2
Other comprehensive loss	(43		)	(25		)	(51		)	68			(51		)
Comprehensive income/(loss)	30			23			(52		)	(44		)	(43		)
Less: Comprehensive income attributable to noncontrolling interest	—			9			—			—			9
Comprehensive income/(loss) attributable to NRG Energy, Inc.	30			14			(52		)	(44		)	(52		)
Dividends for preferred shares	—			—			2			—			2
Comprehensive income/(loss) available for common stockholders	$	30		$	14		$	(54	)	$	(44	)	$	(54	)
(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, 2012
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Net Income	$	310		$	166		$	43		$	(458	)	$	61
Other comprehensive loss, net of tax
Unrealized loss on derivatives, net	(122		)	(33		)	(145		)	168			(132		)
Foreign currency translation adjustments, net	—			(2		)	1			—			(1		)
Foreign currency translation realized upon sale of Schkopau	—			(11		)	—			—			(11		)
Available-for-sale securities, net	—			—			2			—			2
Other comprehensive loss	(122		)	(46		)	(142		)	168			(142		)
Comprehensive income/(loss)	188			120			(99		)	(290		)	(81		)
Less: Comprehensive income attributable to noncontrolling interest	—			18			—			—			18
Comprehensive income/(loss) attributable to NRG Energy, Inc.	188			102			(99		)	(290		)	(99		)
Dividends for preferred shares	—			—			7			—			7
Comprehensive income/(loss) available for common stockholders	$	188		$	102		$	(106	)	$	(290	)	$	(106	)
(a)	All significant intercompany transactions have been eliminated in consolidation.
NRG ENERGY, INC. AND SUBSIDIARIES
CONDENSED CONSOLIDATING BALANCE SHEETS
December 31, 2012
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
ASSETS	(In millions)
Current Assets
Cash and cash equivalents	$	78		$	1,258		$	751		$	—		$	2,087
Funds deposited by counterparties	131			140			—			—			271
Restricted cash	11			196			10			—			217
Accounts receivable, net	807			254			—			—			1,061
Inventory	472			439			—			—			911
Derivative instruments	2,058			604			—			(18		)	2,644
Deferred income taxes	(153		)	10			199			—			56
Cash collateral paid in support of energy risk management activities	81			148			—			—			229
Renewable energy grant receivable	—			58			—			—			58
Prepayments and other current assets	2,966			(57		)	(2,518		)	10			401
Total current assets	6,451			3,050			(1,558		)	(8		)	7,935
Net Property, Plant and Equipment	9,905			10,235			121			(20		)	20,241
Other Assets
Investment in subsidiaries	244			(102		)	17,655			(17,797		)	—
Equity investments in affiliates	33			633			10			—			676
Capital leases and notes receivable, less current portion	3			74			531			(529		)	79
Goodwill	1,944			12			—			—			1,956
Intangible assets, net	1,042			177			33			(52		)	1,200
Nuclear decommissioning trust fund	473			—			—			—			473
Deferred income taxes	(915		)	1,829			368			—			1,282
Derivative instruments	149			515			—			(2		)	662
Other non-current assets	85			305			210			—			600
Total other assets	3,058			3,443			18,807			(18,380		)	6,928
Total Assets	$	19,414		$	16,728		$	17,370		$	(18,408	)	$	35,104
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities
Current portion of long-term debt and capital leases	$	1		$	137		$	15		$	(6	)	$	147
Accounts payable	541			584			46			—			1,171
Accounts payable — affiliate	(55		)	1,421			(1,366		)	—			—
Derivative instruments	1,726			271			2			(18		)	1,981
Cash collateral received in support of energy risk management activities	131			140			—			—			271
Accrued expenses and other current liabilities	354			488			243			—			1,085
Total current liabilities	2,698			3,041			(1,060		)	(24		)	4,655
Other Liabilities
Long-term debt and capital leases	310			8,459			7,496			(529		)	15,736
Nuclear decommissioning reserve	354			—			—			—			354
Nuclear decommissioning trust liability	273			—			—			—			273
Deferred income taxes	—			55			—			—			55
Derivative instruments	312			190			—			(2		)	500
Out-of-market contracts	180			1,082			—			(31		)	1,231
Other non-current liabilities	618			800			135			—			1,553
Total non-current liabilities	2,047			10,586			7,631			(562		)	19,702
Total liabilities	4,745			13,627			6,571			(586		)	24,357
3.625% Preferred Stock	—			—			249			—			249
Stockholders’ Equity	14,669			3,101			10,550			(17,822		)	10,498
Total Liabilities and Stockholders’ Equity	$	19,414		$	16,728		$	17,370		$	(18,408	)	$	35,104
(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, 2012
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated Balance
							(Note Issuer)
	(In millions)
Cash Flows from Operating Activities
Net Cash Provided/(Used) by Operating Activities	1,942			177			(883		)	(178		)	1,058
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	(1,686		)	416			—			1,270			—
Acquisition of businesses, net of cash acquired	—			(17		)	(23		)	—			(40		)
Capital expenditures	(183		)	(2,241		)	(50		)	—			(2,474		)
Increase in restricted cash, net	(2		)	(94		)	—			—			(96		)
Decrease in restricted cash — U.S. DOE projects	—			113			38			—			151
Increase in notes receivable	—			(20		)	(2		)	—			(22		)
Investments in nuclear decommissioning trust fund securities	(341		)	—			—			—			(341		)
Proceeds from sales of nuclear decommissioning trust fund securities	316			—			—			—			316
Proceeds from renewable energy grants	3			46			—			—			49
Proceeds from sale of assets	133			—			4			—			137
Other	13			(8		)	(14		)	—			(9		)
Net Cash Used by Investing Activities	(1,747		)	(1,805		)	(47		)	1,270			(2,329		)
Cash Flows from Financing Activities
Proceeds from intercompany loans	—			—			1,270			(1,270		)	—
Payment of dividends to preferred stockholders	(172		)	(6		)	—			178			—
Payment of intercompany dividends	—			—			(28		)	—			(28		)
Net payment for settlement of acquired derivatives that include financing elements	(65		)	—			—			—			(65		)
Proceeds from issuance of long-term debt	9			1,526			1,006			—			2,541
Sale proceeds and other contributions from noncontrolling interest in subsidiaries	—			316			—			—			316
Payment of debt issuance costs	—			(16		)	(14		)	—			(30		)
Payments for short and long-term debt	—			(51		)	(904		)	—			(955		)
Net Cash (Used)/Provided by Financing Activities	(228		)	1,769			1,330			(1,092		)	1,779
Effect of exchange rate changes on cash and cash equivalents	—			(3		)	—			—			(3		)
Net (Decrease)/Increase in Cash and Cash Equivalents	(33		)	138			400			—			505
Cash and Cash Equivalents at Beginning of Period	44			85			976			—			1,105
Cash and Cash Equivalents at End of Period	$	11		$	223		$	1,376		$	—		$	1,610
(a)	All significant intercompany transactions have been eliminated in consolidation.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policy)	9 Months Ended
	Sep. 30, 2013
Significant Accounting Policies [Abstract]	'
Use of Estimates (Policy)	'
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States 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.
Development Activity Expenses (Policy)	'
	Development Activity Expenses
	Development activity expenses include project development costs, which are expensed in the preliminary stages of a project and capitalized when the project is deemed to be commercially viable. Commercial viability is determined by one or a series of actions including, among others, Board of Director approval pursuant to a formal project plan that subjects the Company to significant future obligations that can only be discharged by the use of a Company asset. When a project is available for operations, capitalized project development costs are reclassified to property, plant and equipment and amortized on a straight-line basis over the estimated useful life of the project's related assets. Capitalized costs are charged to expense if a project is abandoned or management otherwise determines the costs to be unrecoverable.
	Development activity expenses also include selling, general, and administrative expenses associated with the current operations of certain developing businesses including residential solar, electric vehicles, waste-to-energy, carbon capture and other emerging technologies. The revenue associated with these businesses was immaterial for the three and nine months ended September 30, 2013 and 2012. When it is determined that a business will remain an ongoing part of the Company's operations or when operating revenues become material relative to the operating costs of the underlying business, the Company no longer classifies a business as a development activity.
Nuclear Decommissioning (Policy)	'
	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 nuclear decommissioning trust liability and are not included in net income or accumulated other comprehensive income, consistent with regulatory treatment.
Segment Reporting (Policy)	'
	Effective June 2013, the Company's segment structure and its allocation of corporate expenses were updated to reflect how management currently makes financial decisions and allocates resources. The Company has recast data from prior periods to reflect this change in reportable segments to conform to the current year presentation. The Company's businesses are primarily segregated based on the Retail Business, conventional power generation, alternative energy businesses, NRG Yield, and corporate activities.  Within NRG's conventional power generation, there are distinct components with separate operating results and management structures for the following geographical regions: Texas, East, South Central, West and Other, which includes international businesses and maintenance services.  The Company's alternative energy segment includes solar and wind assets, excluding those in the NRG Yield segment, electric vehicle services and the carbon capture business.  NRG Yield includes certain of the Company's contracted generation assets including three natural gas or dual-fired facilities, eight utility-scale solar and wind generation facilities, two portfolios of distributed solar facilities and thermal infrastructure assets. Intersegment sales are accounted for at market.

Basis_of_Presentation_Basis_of

Basis of Presentation Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2013
Basis of Presentation Disclosure [Abstract]	'
IPO of NRG Yield	'
	The following table represents the structure of NRG Yield, Inc. after the initial public offering:

Summary_of_Significant_Account2

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2013
Noncontrolling Interest [Abstract]	'
Schedule of Change in Noncontrolling Interest	'
	The following table reflects the changes in NRG's noncontrolling interest balance:
		(In millions)
	Balance as of December 31, 2012	$	518
	Contributions from noncontrolling interest	289
	Comprehensive income attributable to noncontrolling interest	26
	Balance as of September 30, 2013	$	833

Business_Acquisitions_and_Disp1

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]	'
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	'
	The following table summarizes the provisional amounts recognized for assets acquired and liabilities assumed as of the acquisition date as well as adjustments made during the nine months ended September 30, 2013 to the amounts initially recorded in 2012 due to the ongoing evaluation of initial estimates. The measurement period adjustments were recorded as an adjustment to the gain on bargain purchase and did not have a significant impact on the Company's consolidated statements of operations, cash flows or financial position in any period. The allocation of the purchase price may be modified up to one year from the date of the acquisition as more information is obtained about the fair value of assets acquired and liabilities assumed.
	(In millions)	Amounts Recognized		Measurement Period Adjustments			Amounts Recognized
		as of Acquisition Date					as of Acquisition Date
		(as previously reported)					(as adjusted)
	Assets
	Cash	$	983	$	—		$	983
	Current and non-current assets	1,385		(18		)	1,367
	Property, plant and equipment	3,936		(27		)	3,909
	Derivative assets	1,157		—			1,157
	Deferred income taxes	2,265		21			2,286
	Total assets acquired	$	9,726	$	(24	)	$	9,702
	Liabilities
	Current and non-current liabilities	$	1,312	$	(7	)	$	1,305
	Out-of-market contracts and leases	1,064		15			1,079
	Derivative liabilities	399		—			399
	Long-term debt and capital leases	4,203		3			4,206
	Total liabilities assumed	6,978		11			6,989
	Net assets acquired	2,748		(35		)	2,713
	Consideration paid	2,188		—			2,188
	Gain on bargain purchase	$	560	$	(35	)	$	525

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
Fair Value of Financial Instruments Disclosure [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, 2013				As of December 31, 2012
		Carrying Amount		Fair Value		Carrying Amount			Fair Value
		(In millions)
	Assets:
	Notes receivable (a)	$	107	$	107	$	88		$	88
	Liabilities:
	Long-term debt, including current portion	16,699		17,061		15,866			16,492
	(a) Includes the current portion of notes receivable which is recorded in prepayments and other current assets on the Company's consolidated balance sheet
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, 2013
		Fair Value
	(In millions)	Level 1		Level 2		Level 3			Total
	Investment in available-for-sale securities (classified within other
	non-current assets):
	Debt securities	$	—	$	—	$	15		$	15
	Other (a)	37		—		—			37
	Trust fund investments:
	Cash and cash equivalents	2		—		—			2
	U.S. government and federal agency obligations	51		4		—			55
	Federal agency mortgage-backed securities	—		58		—			58
	Commercial mortgage-backed securities	—		12		—			12
	Corporate debt securities	—		60		—			60
	Equity securities	281		—		55			336
	Foreign government fixed income securities	—		2		—			2
	Derivative assets:
	Commodity contracts	436		1,337		111			1,884
	Interest rate contracts	—		11		—			11
	Total assets	$	807	$	1,484	$	181		$	2,472
	Derivative liabilities:
	Commodity contracts	$	344	$	892	$	118		$	1,354
	Interest rate contracts	—		82		—			82
	Total liabilities	$	344	$	974	$	118		$	1,436
	(a) Primarily consists of mutual funds held in rabbi trusts for non-qualified deferred compensation plans for certain former employees.
		As of December 31, 2012
		Fair Value
	(In millions)	Level 1		Level 2		Level 3			Total
	Investment in available-for-sale securities (classified within other
	non-current assets):
	Debt securities	$	—	$	—	$	12		$	12
	Other (a)	44		—		—			44
	Trust fund investments:
	Cash and cash equivalents	10		—		—			10
	U.S. government and federal agency obligations	34		—		—			34
	Federal agency mortgage-backed securities	—		59		—			59
	Commercial mortgage-backed securities	—		9		—			9
	Corporate debt securities	—		80		—			80
	Equity securities	233		—		47			280
	Foreign government fixed income securities	—		2		—			2
	Derivative assets:
	Commodity contracts	1,457		1,711		135			3,303
	Interest rate contracts	—		3		—			3
	Total assets	$	1,778	$	1,864	$	194		$	3,836
	Derivative liabilities:
	Commodity contracts	$	1,144	$	1,047	$	147		$	2,338
	Interest rate contracts	—		143		—			143
	Total liabilities	$	1,144	$	1,190	$	147		$	2,481
	(a) Primarily consists of mutual funds held in rabbi trusts for non-qualified deferred compensation plans for certain former employees.
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, 2013 and 2012, the 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:
		Fair Value Measurement Using Significant Unobservable Inputs (Level 3)
		Three months ended September 30, 2013										Nine months ended September 30, 2013
	(In millions)	Debt Securities		Trust Fund Investments		Derivatives(a)			Total			Debt Securities		Trust Fund Investments		Derivatives(a)			Total
	Beginning balance	$	15	$	50	$	(12	)	$	53		$	12	$	47	$	(12	)	$	47
	Total gains/(losses) — realized/unrealized:
	Included in earnings	—		—		14			14			—		—		(4		)	(4		)
	Included in OCI	—		—		—			—			3		—		—			3
	Included in nuclear decommissioning obligations	—		5		—			5			—		7		—			7
	Purchases	—		—		4			4			—		1		(3		)	(2		)
	Transfers into Level 3 (b)	—		—		(36		)	(36		)	—		—		(9		)	(9		)
	Transfers out of Level 3 (b)	—		—		23			23			—		—		21			21
	Ending balance as of	$	15	$	55	$	(7	)	$	63		$	15	$	55	$	(7	)	$	63
	September 30, 2013
	Gains 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, 2013	$	—	$	—	$	(7	)	$	(7	)	$	—	$	—	$	(4	)	$	(4	)
	(a)	Consists of derivative assets and liabilities, net.
	(b)	Transfers in/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, 2012										Nine months ended September 30, 2012
	(In millions)	Debt Securities		Trust Fund Investments		Derivatives(a)			Total			Debt Securities		Trust Fund Investments		Derivatives(a)			Total
	Beginning balance	$	9	$	43	$	171		$	223		$	7	$	42	$	8		$	57
	Total (losses)/gains — realized/unrealized:
	Included in earnings	—		—		(9		)	(9		)	—		—		(3		)	(3		)
	Included in OCI	2		—		—			2			4		—		—			4
	Included in nuclear decommissioning obligations	—		3		—			3			—		3		—			3
	Purchases	—		—		(109		)	(109		)	—		1		(1		)	—
	Transfers into Level 3 (b)	—		—		(31		)	(31		)	—		—		4			4
	Transfers out of Level 3 (b)	—		—		(20		)	(20		)	—		—		(6		)	(6		)
	Ending balance as of	$	11	$	46	$	2		$	59		$	11	$	46	$	2		$	59
	September 30, 2012
	(Losses)/gains 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, 2012	$	—	$	—	$	(5	)	$	(5	)	$	—	$	—	$	1		$	1
	(a)	Consists of derivative assets and liabilities, net.
	(b)	Transfers in/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.
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)
	Category	(% of Total)
	Financial institutions	58	%
	Utilities, energy merchants, marketers and other	34
	ISOs	6
	Coal and emissions	2
	Total as of September 30, 2013	100	%
		Net Exposure (a)
	Category	(% of Total)
	Investment grade	96	%
	Non-rated (b)	4
	Total as of September 30, 2013	100	%
	(a)	Counterparty credit exposure excludes uranium and coal transportation contracts because of the unavailability of market prices.
	(b)	For non-rated counterparties, a significant portion are related to ISO and municipal public power entities, which are considered investment grade equivalent ratings based on NRG's internal credit ratings.

Nuclear_Decommissioning_Trust_1

Nuclear Decommissioning Trust Fund (Tables)	9 Months Ended
	Sep. 30, 2013
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, 2013							As of December 31, 2012
	(In millions, except otherwise noted)	Fair Value		Unrealized Gains		Unrealized Losses		Weighted-average Maturities (In years)	Fair Value		Unrealized Gains (a)		Weighted-average Maturities (In years)
	Cash and cash equivalents	$	2	$	—	$	—	—	$	10	$	—	—
	U.S. government and federal agency obligations	54		2		1		9	33		2		10
	Federal agency mortgage-backed securities	58		1		1		24	59		2		23
	Commercial mortgage-backed securities	12		—		—		29	9		—		30
	Corporate debt securities	60		2		1		9	80		4		11
	Equity securities	336		187		—		—	280		143		—
	Foreign government fixed income securities	2		—		—		9	2		—		6
	Total	$	524	$	192	$	3		$	473	$	151
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,
		2013		2012
		(In millions)
	Realized gains	$	10	$	8
	Realized losses	7		5
	Proceeds from sale of securities	344		316

Accounting_for_Derivative_Inst1

Accounting for Derivative Instruments and Hedging Activities (Tables)	9 Months Ended
	Sep. 30, 2013
Accounting for 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 commodity, excluding those derivatives that qualified for the NPNS exception as of September 30, 2013 and December 31, 2012. 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, 2013				December 31, 2012
	Commodity	Units	(In millions)
	Emissions	Short Ton	(1		)		(1		)
	Coal	Short Ton	42				37
	Natural Gas	MMBtu	(215		)		(413		)
	Oil	Barrel	—				1
	Power	MWh	(16		)		(14		)
	Interest	Dollars	$	1,520			$	2,612
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, 2013				December 31, 2012				September 30, 2013				December 31, 2012
		(In millions)
	Derivatives designated as cash flow hedges:
	Interest rate contracts current	$	—			$	—			$	27			$	29
	Interest rate contracts long-term	8				3				47				96
	Commodity contracts current	—				—				2				3
	Commodity contracts long-term	—				—				1				1
	Total derivatives designated as cash flow hedges	8				3				77				129
	Derivatives not designated as cash flow hedges:
	Interest rate contracts current	—				—				5				7
	Interest rate contracts long-term	3				—				3				11
	Commodity contracts current	1,389				2,644				1,030				1,942
	Commodity contracts long-term	495				659				321				392
	Total derivatives not designated as cash flow hedges	1,887				3,303				1,359				2,352
	Total derivatives	$	1,895			$	3,306			$	1,436			$	2,481
Offsetting of derivatives by counterparty master agreement level and collateral received or paid	'
	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, 2013		(In millions)
	Commodity contracts:
	Derivative assets		$	1,884			$	(1,151	)		$	(195	)		$	538
	Derivative liabilities		(1,354		)		1,151				65				(138		)
	Total commodity contracts		530				—				(130		)		400
	Interest rate contracts:
	Derivative assets		11				(6		)		—				5
	Derivative liabilities		(82		)		6				—				(76		)
	Total interest rate contracts		(71		)		—				—				(71		)
	Total derivative instruments		$	459			$	—			$	(130	)		$	329
			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, 2012		(In millions)
	Commodity contracts:
	Derivative assets		$	3,303			$	(2,024	)		$	(374	)		$	905
	Derivative liabilities		(2,338		)		2,024				28				(286		)
	Total commodity contracts		965				—				(346		)		619
	Interest rate contracts:
	Derivative assets		3				—				—				3
	Derivative liabilities		(143		)		—				—				(143		)
	Total interest rate contracts		(140		)		—				—				(140		)
	Total derivative instruments		$	825			$	—			$	(346	)		$	479
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, Derivatives and Hedging, or ASC 815, on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax:
		Three months ended September 30, 2013												Nine months ended September 30, 2013
		Energy Commodities				Interest Rate				Total				Energy Commodities				Interest Rate			Total
		(In millions)
	Accumulated OCI beginning balance	$	24			$	(31	)		$	(7	)		$	41			$	(72	)	$	(31	)
	Reclassified from accumulated OCI to income:
	Due to realization of previously deferred amounts	(15		)		2				(13		)		(38		)		6			(32		)
	Mark-to-market of cash flow hedge accounting contracts	1				(4		)		(3		)		7				33			40
	Accumulated OCI ending balance, net of $13 tax	$	10			$	(33	)		$	(23	)		$	10			$	(33	)	$	(23	)
	Gains/(losses) expected to be realized from OCI during the next 12 months, net of $1 tax	$	11			$	(9	)		$	2			$	11			$	(9	)	$	2
	Gains recognized in income from the ineffective portion of cash flow hedges	$	1			$	—			$	1			$	—			$	—		$	—
		Three months ended September 30, 2012												Nine months ended September 30, 2012
		Energy Commodities				Interest Rate				Total				Energy Commodities				Interest Rate			Total
		(In millions)
	Accumulated OCI beginning balance	$	111			$	(68	)		$	43			$	188			$	(56	)	$	132
	Reclassified from accumulated OCI to income:
	Due to realization of previously deferred amounts	(30		)		3				(27		)		(106		)		11			(95		)
	Mark-to-market of cash flow hedge accounting contracts	(1		)		(15		)		(16		)		(2		)		(35		)	(37		)
	Accumulated OCI ending balance, net of $12 tax	$	80			$	(80	)		$	—			$	80			$	(80	)	$	—
	Gains/(losses) expected to be realized from OCI during the next 12 months, net of $38 tax	$	77			$	(11	)		$	66			$	77			$	(11	)	$	66
	Losses recognized in income from the ineffective portion of cash flow hedges	$	—			$	—			$	—			$	(51	)		$	—		$	(51	)
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, ineffectiveness on cash flow hedges and trading activity on the Company's statement of operations. The effect of commodity hedges is included within operating revenues and cost of operations and the effect of interest rate hedges is included in interest expense.
		Three months ended September 30,								Nine months ended September 30,
		2013				2012				2013				2012
	Unrealized mark-to-market results	(In millions)
	Reversal of previously recognized unrealized gains on settled positions related to economic hedges	$	(48	)		$	(85	)		$	(80	)		$	(160	)
	Reversal of (gain)/loss positions acquired as part of the Reliant Energy, Green Mountain Energy and GenOn acquisitions	(82		)		(15		)		(269		)		5
	Net unrealized gains/(losses) on open positions related to economic hedges	76				(159		)		131				(78		)
	Gains/(losses) on ineffectiveness associated with open positions treated as	1				—				—				(51		)
	cash flow hedges
	Total unrealized mark-to-market losses for economic hedging activities	(53		)		(259		)		(218		)		(284		)
	Reversal of previously recognized unrealized gains on settled positions related to trading activity	(13		)		(15		)		(42		)		(45		)
	Reversal of gain positions acquired as part of the GenOn acquisitions	(2		)		—				(2		)		—
	Net unrealized gains/(losses) on open positions related to trading activity	26				(3		)		—				33
	Total unrealized mark-to-market gains/(losses) for trading activity	11				(18		)		(44		)		(12		)
	Total unrealized losses	$	(42	)		$	(277	)		$	(262	)		$	(296	)
		Three months ended September 30,								Nine months ended September 30,
		2013				2012				2013				2012
		(In millions)
	Unrealized losses included in operating revenues	$	(64	)		$	(395	)		$	(404	)		$	(470	)
	Unrealized gains included in cost of operations	22				118				142				174
	Total impact to statement of operations — energy commodities	$	(42	)		$	(277	)		$	(262	)		$	(296	)
	Total impact to statement of operations — interest rate contracts	$	4			$	—			$	10			$	(12	)

Debt_and_Capital_Leases_Debt_a

Debt and Capital Leases Debt and Capital Leases (Tables)	9 Months Ended
	Sep. 30, 2013
Long Term Debt Disclosure [Abstract]	'
Long-term debt and capital leases	'
	Long-term debt and capital leases consisted of the following:
		September 30, 2013		December 31, 2012		Current interest rate % (a)
	(In millions, except rates)
	NRG recourse debt:
	Senior notes, due 2018	$	1,130	$	1,200	7.625
	Senior notes, due 2019	800		800		7.625
	Senior notes, due 2019	601		693		8.5
	Senior notes, due 2020	1,063		1,100		8.25
	Senior notes, due 2021	1,128		1,128		7.875
	Senior notes, due 2023	990		990		6.625
	Term loan facility, due 2018	2,006		1,573		L+2.00
	Indian River Power LLC, tax-exempt bonds, due 2040 and 2045	247		247		5.375 - 6.000
	Dunkirk Power LLC, tax-exempt bonds, due 2042	59		59		5.875
	Fort Bend County, tax-exempt bonds, due 2038 and 2042	67		28		4.75
	Subtotal NRG Recourse Debt	8,091		7,818
	NRG non-recourse debt:
	GenOn senior notes, due 2014	—		617		7.625
	GenOn senior notes, due 2017	787		800		7.875
	GenOn senior notes, due 2018	785		801		9.5
	GenOn senior notes, due 2020	624		631		9.875
	GenOn Americas Generation senior notes, due 2021	504		509		8.5
	GenOn Americas Generation senior notes, due 2031	435		437		9.125
	NRG Marsh Landing, due 2017 and 2023	500		390		L+2.50 - 2.75
	CVSR - High Plains Ranch II LLC, due 2013 and 2037	1,104		786		0.611 - 3.579
	NRG West Holdings LLC, due 2023	475		350		L+2.25 - 2.75
	Agua Caliente Solar LLC, due 2037	764		640		2.395 - 3.473
	Ivanpah Financing, due 2014 and 2038	1,561		1,437		1.116 - 4.256
	South Trent Wind LLC, due 2020	69		72		L+2.625
	NRG Peaker Finance Co. LLC, bonds, due 2019	176		173		L+1.07
	NRG Energy Center Minneapolis LLC, senior secured notes, due 2013, 2017 and 2025	129		137		5.95 - 7.25
	NRG Solar Alpine LLC, due 2013 and 2022	223		2		L+2.25 - 2.50
	NRG Solar Borrego I LLC, due 2024 and 2038	79		—		L+2.50/5.65
	NRG Solar Avra Valley LLC	64		66		L+2.25
	TA - High Desert LLC, due 2013, 2023 and 2033	82		—		L+2.50/5.15
	NRG Solar Kansas South LLC, due 2013 and 2031	59		—		L+2.00 - 2.625
	Other	188		200		various
	Subtotal NRG Non-Recourse Debt	8,608		8,048
	Subtotal long-term debt (including current maturities)	16,699		15,866
	Capital leases:
	Chalk Point capital lease, due 2015	11		14		8.19
	Other	3		3		various
	Subtotal long-term debt and capital leases (including current maturities)	16,713		15,883
	Less current maturities	911		147
	Total long-term debt and capital leases	$	15,802	$	15,736
	(a) As of September 30, 2013, L+ equals 3 month LIBOR plus x%, with the exception of NRG Solar Alpine LLC cash grant loan and NRG Solar Kansas South LLC cash grant bridge loan which are 1 month LIBOR plus x% and NRG Solar Kansas South LLC term loan which is 6 month LIBOR plus x%.

Changes_in_Capital_Structure_T

Changes in Capital Structure (Tables)	9 Months Ended
	Sep. 30, 2013
Changes in Capital Structure Disclosure [Abstract]	'
Changes in NRG's common shares issued and outstanding	'
	The following table reflects the changes in NRG's common shares issued and outstanding:
		Issued		Treasury			Outstanding
	Balance as of December 31, 2012	399,112,616		(76,505,718	)		322,606,898
	Shares issued under LTIP	1,562,480		—			1,562,480
	Shares issued under ESPP	—		130,482			130,482
	Shares repurchased under Capital Allocation Program	—		(972,292	)		(972,292	)
	Balance as of September 30, 2013	400,675,096		(77,347,528	)		323,327,568
Schedule of dividends paid	'
	The following table lists the dividends paid during 2013:
		First Quarter 2013			Second Quarter 2013				Third Quarter 2013
	Dividends per Common Share	$	0.09		$	0.12			$	0.12

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings (Loss) Per Share Disclosure [Abstract]	'
Reconciliation of NRG's basic and diluted earnings per share	'
	The reconciliation of NRG's basic and diluted earnings/(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)	2013			2012			2013			2012
	Basic earnings/(loss) per share attributable to NRG common stockholders
	Net income/(loss) attributable to NRG Energy, Inc.	$	124		$	(1	)	$	(74	)	$	43
	Dividends for preferred shares	2			2			7			7
	Income/(loss) Available for Common Stockholders	$	122		$	(3	)	$	(81	)	$	36
	Weighted average number of common shares outstanding	323			228			323			228
	Earnings/(loss) per weighted average common share — basic	$	0.38		$	(0.01	)	$	(0.25	)	$	0.16
	Diluted earnings/(loss) per share attributable to NRG common stockholders
	Weighted average number of common shares outstanding	323			228			323			228
	Incremental shares attributable to the issuance of equity compensation (treasury stock method)	4			—			—			2
	Total dilutive shares	327			228			323			230
	Earnings/(loss) per weighted average common share — diluted	$	0.37		$	(0.01	)	$	(0.25	)	$	0.16
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 earnings/(loss) per share:
		Three months ended September 30,					Nine months ended September 30,
	(In millions of shares)	2013		2012			2013		2012
	Equity compensation plans	2		11			10		6
	Embedded derivative of 3.625% redeemable perpetual preferred stock	16		16			16		16
	Total	18		27			26		22

Segment_Reporting_Tables

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting Disclosure [Abstract]	'
Schedule of segment reporting information, by segment	'
	(In millions)				Conventional Power Generation
	Three months ended September 30, 2013	Retail(a)			Texas(a)			East(a)			South(a)		West(a)			Other(a)		Alternative Energy(a)			NRG Yield(a)			Corporate(a)(b)			Elimination			Total
											Central
	Operating revenues	$	1,994		$	881		$	1,011		$	244	$	134		$	38	$	83		$	95		$	—		$	(990	)	$	3,490
	Depreciation and amortization	37			116			79			24		13			1		27			16			5			—			318
	Equity in earnings/(losses) of unconsolidated affiliates	—			—			—			1		(10		)	—		(3		)	12			—			(5		)	(5		)
	(Loss)/income before income taxes	(60		)	265			245			17		30			1		1			45			(217		)	(21		)	306
	Net (loss)/income attributable to NRG Energy, Inc.	$	(60	)	$	265		$	245		$	17	$	30		$	1	$	(21	)	$	31		$	(375	)	$	(9	)	$	124
	Total assets as of September 30, 2013	$	4,296		$	11,914		$	8,329		$	2,290	$	1,553		$	461	$	6,162		$	2,331		$	4,863		$	(7,336	)	$	34,863
	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	2		$	910		$	55		$	—	$	—		$	15	$	8		$	—		$	—
	(b) Includes loss on debt extinguishment of $1 million.
	(In millions)				Conventional Power Generation
	Three months ended September 30, 2012	Retail(c)			Texas(c)			East(c)			South(c)		West(c)			Other(c)		Alternative Energy(c)			NRG Yield(c)			Corporate(c)(d)			Elimination			Total
											Central
	Operating revenues	$	1,856		$	877		$	274		$	270	$	87		$	28	$	49		$	47		$	4		$	(1,161	)	$	2,331
	Depreciation and amortization	41			115			32			23		3			1		15			6			3			—			239
	Equity in earnings/(losses) of unconsolidated affiliates	—			—			—			—		4			3		(9		)	6			—			—			4
	(Loss)/income before income taxes	(300		)	299			30			19		35			5		(8		)	12			(197		)	—			(105		)
	Net (loss)/income attributable to NRG Energy, Inc.	$	(300	)	$	299		$	30		$	19	$	35		$	5	$	(16	)	$	4		$	(77	)	$	—		$	(1	)
	(c) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	3		$	1,126		$	6		$	—	$	—		$	12	$	10		$	—		$	4
	(d) Includes loss on debt extinguishment of $41 million.
	(In millions)				Conventional Power Generation
	Nine months ended September 30, 2013	Retail(e)			Texas(e)			East(e)			South(e)		West(e)			Other(e)		Alternative Energy(e)			NRG Yield(e)			Corporate(e)(f)			Elimination			Total
											Central
	Operating revenues	$	4,760		$	1,712		$	2,432		$	656	$	347		$	110	$	177		$	227		$	9		$	(1,930	)	$	8,500
	Depreciation and amortization	105			340			236			73		37			3		78			35			14			—			921
	Equity in (losses)/earnings of unconsolidated affiliates	—			—			—			3		(8		)	2		(7		)	18			—			(2		)	6
	Income/(loss) before income taxes	231			14			238			17		62			3		(48		)	90			(695		)	(6		)	(94		)
	Net income/(loss) attributable to NRG Energy, Inc.	$	231		$	14		$	238		$	17	$	62		$	2	$	(75	)	$	76		$	(642	)	$	3		$	(74	)
	(e) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	4		$	1,732		$	99		$	16	$	3		$	48	$	19		—		$	9
	(f) Includes loss on debt extinguishment of $50 million.
	(In millions)				Conventional Power Generation
	Nine months ended September 30, 2012	Retail(g)			Texas(g)			East(g)			South(g)		West			Other(g)		Alternative Energy(g)			NRG Yield(g)			Corporate(g)(h)			Elimination			Total
											Central
	Operating revenues	$	4,492		$	1,462		$	598		$	653	$	185		$	152	$	91		$	133		$	11		$	(1,418	)	$	6,359
	Depreciation and amortization	126			343			96			69		8			1		34			18			8			—			703
	Equity in earnings/(losses) of unconsolidated affiliates	—			—			—			—		6			8		(3		)	15			—			$	—		$	26
	Income/(loss) before income taxes	504			(202		)	(31		)	—		42			22		(27		)	18			(511		)	—			(185		)
	Net income/(loss) attributable to NRG Energy, Inc.	$	504		$	(202	)	$	(31	)	$	—	$	42		$	18	$	(45	)	$	8		$	(251	)	$	—		$	43
	(g) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	3		$	1,287		$	51		$	—	$	—		$	55	$	18		$	—		$	4
	(h) Includes loss on debt extinguishment of $41 million.

Income_Taxes_Tables

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2013
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 otherwise noted)	2013			2012			2013		2012
	Income/(loss) before income taxes	$	306		$	(105	)	(94	)	$	(185	)
	Income tax expense/(benefit)	163			(113		)	(47	)	(246		)
	Effective tax rate	53.3		%	107.6		%	50	%	133		%

Condensed_Consolidating_Financ1

Condensed Consolidating Financial Information (Tables)	9 Months Ended
	Sep. 30, 2013
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, 2013
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Operating Revenues
	Total operating revenues	$	2,464		$	1,019		$	—		$	7		$	3,490
	Operating Costs and Expenses
	Cost of operations	1,792			566			(6		)	3			2,355
	Depreciation and amortization	213			102			3			—			318
	Selling, general and administrative	116			70			39			4			229
	Acquisition-related transaction and integration costs	—			13			13			—			26
	Development activity expenses	—			14			13			—			27
	Total operating costs and expenses	2,121			765			62			7			2,955
	Operating Income/(Loss)	343			254			(62		)	—			535
	Other Income/(Expense)
	Equity in (loss)/earnings of consolidated subsidiaries	(25		)	(5		)	309			(279		)	—
	Equity in (loss)/earnings of unconsolidated affiliates	(10		)	10			—			(5		)	(5		)
	Other income, net	5			3			1			(4		)	5
	Loss on debt extinguishment	—			(1		)	—			—			(1		)
	Interest expense	(3		)	(88		)	(137		)	—			(228		)
	Total other (expense)/income	(33		)	(81		)	173			(288		)	(229		)
	Income Before Income Taxes	310			173			111			(288		)	306
	Income tax expense/(benefit)	126			59			(22		)	—			163
	Net Income	184			114			133			(288		)	143
	Less: Net income attributable to noncontrolling interest	—			32			9			(22		)	19
	Net Income attributable to	$	184		$	82		$	124		$	(266	)	$	124
	NRG Energy, Inc.
	(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, 2013
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Operating Revenues
	Total operating revenues	$	6,225		$	2,394		$	—		$	(119	)	$	8,500
	Operating Costs and Expenses
	Cost of operations	4,697			1,593			1			(112		)	6,179
	Depreciation and amortization	624			288			9			—			921
	Selling, general and administrative	341			173			164			(7		)	671
	Acquisition-related transaction and integration costs	—			54			41			—			95
	Development activity expenses	—			24			39			—			63
	Total operating costs and expenses	5,662			2,132			254			(119		)	7,929
	Operating Income/(Loss)	563			262			(254		)	—			571
	Other Income/(Expense)
	Equity in (loss)/earnings of consolidated subsidiaries	(4		)	(9		)	363			(350		)	—
	Equity in (loss)/earnings of unconsolidated affiliates	(8		)	16			—			(2		)	6
	Other income, net	7			5			3			(6		)	9
	Loss on debt extinguishment	—			(12		)	(38		)	—			(50		)
	Interest expense	(13		)	(229		)	(388		)	—			(630		)
	Total other expense	(18		)	(229		)	(60		)	(358		)	(665		)
	Income/(Loss) Before Income Taxes	545			33			(314		)	(358		)	(94		)
	Income tax expense/(benefit)	212			(10		)	(249		)	—			(47		)
	Net Income/(Loss)	333			43			(65		)	(358		)	(47		)
	Less: Net income attributable to noncontrolling interest	—			40			9			(22		)	27
	Net Income/(Loss) attributable to	$	333		$	3		$	(74	)	$	(336	)	$	(74	)
	NRG Energy, Inc.
	(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, 2012
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Operating Revenues
Total operating revenues	$	2,237		$	120		$	—		$	(26	)	$	2,331
Operating Costs and Expenses
Cost of operations	1,715			47			1			(23		)	1,740
Depreciation and amortization	217			20			2			—			239
Selling, general and administrative	154			—			73			(3		)	224
Acquisition-related transaction and integration costs	—			—			18			—			18
Development activity expenses	—			14			10			—			24
Total operating costs and expenses	2,086			81			104			(26		)	2,245
Operating Income/(Loss)	151			39			(104		)	—			86
Other Income/(Expense)
Equity in (losses)/earnings of consolidated subsidiaries	(10		)	1			121			(112		)	—
Equity in earnings of unconsolidated affiliates	4			—			—			—			4
Other income, net	—			2			7			—			9
Loss on debt extinguishment	—			—			(41		)	—			(41		)
Interest expense	(5		)	(21		)	(137		)	—			(163		)
Total other expense	(11		)	(18		)	(50		)	(112		)	(191		)
Income/(Loss) Before Income Taxes	140			21			(154		)	(112		)	(105		)
Income tax expense/(benefit)	67			(27		)	(153		)	—			(113		)
Net Income/(Loss)	73			48			(1		)	(112		)	8
Less: Net income attributable to noncontrolling interest	—			9			—			—			9
Net Income/(Loss) attributable to NRG Energy, Inc.	$	73		$	39		$	(1	)	$	(112	)	$	(1	)
(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, 2012
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Operating Revenues
Total operating revenues	$	6,058		$	353		$	—		$	(52	)	$	6,359
Operating Costs and Expenses
Cost of operations	4,512			186			7			(45		)	4,660
Depreciation and amortization	647			48			8			—			703
Selling, general and administrative	387			6			227			(7		)	613
Acquisition-related transaction and integration costs	—			—			18			—			18
Development activity expenses	—			22			30			—			52
Total operating costs and expenses	5,546			262			290			(52		)	6,046
Operating Income/(Loss)	512			91			(290		)	—			313
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	6			(11		)	463			(458		)	—
Equity in earnings of unconsolidated affiliates	6			20			—			—			26
Other income, net	—			4			8			—			12
Loss on debt extinguishment	—			—			(41		)	—			(41		)
Interest expense	(21		)	(60		)	(414		)	—			(495		)
Total other (expense)/income	(9		)	(47		)	16			(458		)	(498		)
Income/(Loss) Before Income Taxes	503			44			(274		)	(458		)	(185		)
Income tax expense/(benefit)	193			(122		)	(317		)	—			(246		)
Net Income	310			166			43			(458		)	61
Less: Net income attributable to noncontrolling interest	—			18			—			—			18
Net Income attributable to NRG Energy, Inc.	$	310		$	148		$	43		$	(458	)	$	43
(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
	For the Three Months Ended September 30, 2013
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Net Income	$	184		$	114		$	133		$	(288	)	$	143
	Other comprehensive (loss)/income, net of tax
	Unrealized (loss)/gain on derivatives, net	(13		)	(8		)	17			(12		)	(16		)
	Foreign currency translation adjustments, net	—			4			1			—			5
	Other comprehensive (loss)/income	(13		)	(4		)	18			(12		)	(11		)
	Comprehensive income	171			110			151			(300		)	132
	Less: Comprehensive income attributable to noncontrolling interest	—			29			9			(20		)	18
	Comprehensive income attributable to NRG Energy, Inc.	171			81			142			(280		)	114
	Dividends for preferred shares	—			—			2			—			2
	Comprehensive income available for common stockholders	$	171		$	81		$	140		$	(280	)	$	112
	(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, 2013
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Net Income/(Loss)	$	333		$	43		$	(65	)	$	(358	)	$	(47	)
	Other comprehensive (loss)/income, net of tax
	Unrealized (loss)/gain on derivatives, net	(54		)	41			9			12			8
	Foreign currency translation adjustments, net	—			(11		)	(3		)	—			(14		)
	Available-for-sale securities, net	—			—			2			—			2
	Defined benefit plan, net	—			25			—			—			25
	Other comprehensive (loss)/income	(54		)	55			8			12			21
	Comprehensive income/(loss)	279			98			(57		)	(346		)	(26		)
	Less: Comprehensive income attributable to noncontrolling interest	—			39			9			(22		)	26
	Comprehensive income/(loss) attributable to NRG Energy, Inc.	279			59			(66		)	(324		)	(52		)
	Dividends for preferred shares	—			—			7			—			7
	Comprehensive income/(loss) available for common stockholders	$	279		$	59		$	(73	)	$	(324	)	$	(59	)
	(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, 2012
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Net Income/(Loss)	$	73		$	48		$	(1	)	$	(112	)	$	8
	Other comprehensive loss, net of tax
	Unrealized loss on derivatives, net	(43		)	(14		)	(54		)	68			(43		)
	Foreign currency translation adjustments, net	—			—			1			—			1
	Foreign currency translation realized upon sale of Schkopau	—			(11		)	—			—			(11		)
	Available-for-sale securities, net	—			—			2			—			2
	Other comprehensive loss	(43		)	(25		)	(51		)	68			(51		)
	Comprehensive income/(loss)	30			23			(52		)	(44		)	(43		)
	Less: Comprehensive income attributable to noncontrolling interest	—			9			—			—			9
	Comprehensive income/(loss) attributable to NRG Energy, Inc.	30			14			(52		)	(44		)	(52		)
	Dividends for preferred shares	—			—			2			—			2
	Comprehensive income/(loss) available for common stockholders	$	30		$	14		$	(54	)	$	(44	)	$	(54	)
	(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, 2012
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
(Note Issuer)
	(In millions)
Net Income	$	310		$	166		$	43		$	(458	)	$	61
Other comprehensive loss, net of tax
Unrealized loss on derivatives, net	(122		)	(33		)	(145		)	168			(132		)
Foreign currency translation adjustments, net	—			(2		)	1			—			(1		)
Foreign currency translation realized upon sale of Schkopau	—			(11		)	—			—			(11		)
Available-for-sale securities, net	—			—			2			—			2
Other comprehensive loss	(122		)	(46		)	(142		)	168			(142		)
Comprehensive income/(loss)	188			120			(99		)	(290		)	(81		)
Less: Comprehensive income attributable to noncontrolling interest	—			18			—			—			18
Comprehensive income/(loss) attributable to NRG Energy, Inc.	188			102			(99		)	(290		)	(99		)
Dividends for preferred shares	—			—			7			—			7
Comprehensive income/(loss) available for common stockholders	$	188		$	102		$	(106	)	$	(290	)	$	(106	)
(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, 2013
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
	ASSETS	(In millions)
	Current Assets
	Cash and cash equivalents	$	23		$	1,110		$	996		$	—		$	2,129
	Funds deposited by counterparties	—			122			—			—			122
	Restricted cash	18			278			11			—			307
	Accounts receivable, net	1,132			234			—			—			1,366
	Inventory	406			455			—			—			861
	Derivative instruments	914			491			—			(16		)	1,389
	Cash collateral paid in support of energy risk management activities	253			35			—			—			288
	Renewable energy grant receivable	—			344			1			—			345
	Prepayments and other current assets	4,103			283			(3,414		)	(530		)	442
	Total current assets	6,849			3,352			(2,406		)	(546		)	7,249
	Net property, plant and equipment	9,651			10,822			149			(22		)	20,600
	Other Assets
	Investment in subsidiaries	108			(108		)	18,218			(18,218		)	—
	Equity investments in affiliates	18			724			10			(126		)	626
	Notes receivable, less current portion	—			66			255			(245		)	76
	Goodwill	1,941			12			—			—			1,953
	Intangible assets, net	988			172			33			(52		)	1,141
	Nuclear decommissioning trust fund	524			—			—			—			524
	Deferred income tax	—			784			715			—			1,499
	Derivative instruments	202			307			—			(3		)	506
	Other non-current assets	80			239			370			—			689
	Total other assets	3,861			2,196			19,601			(18,644		)	7,014
	Total Assets	$	20,361		$	16,370		$	17,344		$	(19,212	)	$	34,863
	LIABILITIES AND STOCKHOLDERS’ EQUITY
	Current Liabilities
	Current portion of long-term debt and capital leases	$	1		$	890		$	20		$	—		$	911
	Accounts payable	678			436			26			—			1,140
	Accounts payable — affiliate	6			1,973			(1,572		)	(407		)	—
	Derivative instruments	887			193			—			(16		)	1,064
	Deferred income taxes	369			(264		)	7			—			112
	Cash collateral received in support of energy risk management activities	—			122			—			—			122
	Accrued expenses and other current liabilities	283			478			272			—			1,033
	Total current liabilities	2,224			3,828			(1,247		)	(423		)	4,382
	Other Liabilities
	Long-term debt and capital leases	316			7,965			7,766			(245		)	15,802
	Nuclear decommissioning reserve	290			—			—			—			290
	Nuclear decommissioning trust liability	303			—			—			—			303
	Deferred income taxes	886			(836		)	—			—			50
	Derivative instruments	279			96			—			(3		)	372
	Out-of-market contracts	162			1,026			—			(31		)	1,157
	Other non-current liabilities	510			631			236			—			1,377
	Total non-current liabilities	2,746			8,882			8,002			(279		)	19,351
	Total liabilities	4,970			12,710			6,755			(702		)	23,733
	3.625% convertible perpetual preferred stock	—			—			249			—			249
	Stockholders’ Equity	15,391			3,660			10,340			(18,510		)	10,881
	Total Liabilities and Stockholders’ Equity	$	20,361		$	16,370		$	17,344		$	(19,212	)	$	34,863
	(a)	All significant intercompany transactions have been eliminated in consolidation.
	NRG ENERGY, INC. AND SUBSIDIARIES
	CONDENSED CONSOLIDATING BALANCE SHEETS
	December 31, 2012
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
	ASSETS	(In millions)
	Current Assets
	Cash and cash equivalents	$	78		$	1,258		$	751		$	—		$	2,087
Funds deposited by counterparties	131			140			—			—			271
Restricted cash	11			196			10			—			217
Accounts receivable, net	807			254			—			—			1,061
Inventory	472			439			—			—			911
Derivative instruments	2,058			604			—			(18		)	2,644
Deferred income taxes	(153		)	10			199			—			56
Cash collateral paid in support of energy risk management activities	81			148			—			—			229
Renewable energy grant receivable	—			58			—			—			58
Prepayments and other current assets	2,966			(57		)	(2,518		)	10			401
Total current assets	6,451			3,050			(1,558		)	(8		)	7,935
Net Property, Plant and Equipment	9,905			10,235			121			(20		)	20,241
Other Assets
Investment in subsidiaries	244			(102		)	17,655			(17,797		)	—
Equity investments in affiliates	33			633			10			—			676
Capital leases and notes receivable, less current portion	3			74			531			(529		)	79
Goodwill	1,944			12			—			—			1,956
Intangible assets, net	1,042			177			33			(52		)	1,200
Nuclear decommissioning trust fund	473			—			—			—			473
Deferred income taxes	(915		)	1,829			368			—			1,282
Derivative instruments	149			515			—			(2		)	662
Other non-current assets	85			305			210			—			600
Total other assets	3,058			3,443			18,807			(18,380		)	6,928
Total Assets	$	19,414		$	16,728		$	17,370		$	(18,408	)	$	35,104
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities
Current portion of long-term debt and capital leases	$	1		$	137		$	15		$	(6	)	$	147
Accounts payable	541			584			46			—			1,171
Accounts payable — affiliate	(55		)	1,421			(1,366		)	—			—
Derivative instruments	1,726			271			2			(18		)	1,981
Cash collateral received in support of energy risk management activities	131			140			—			—			271
Accrued expenses and other current liabilities	354			488			243			—			1,085
Total current liabilities	2,698			3,041			(1,060		)	(24		)	4,655
Other Liabilities
Long-term debt and capital leases	310			8,459			7,496			(529		)	15,736
Nuclear decommissioning reserve	354			—			—			—			354
Nuclear decommissioning trust liability	273			—			—			—			273
Deferred income taxes	—			55			—			—			55
Derivative instruments	312			190			—			(2		)	500
Out-of-market contracts	180			1,082			—			(31		)	1,231
Other non-current liabilities	618			800			135			—			1,553
Total non-current liabilities	2,047			10,586			7,631			(562		)	19,702
Total liabilities	4,745			13,627			6,571			(586		)	24,357
3.625% Preferred Stock	—			—			249			—			249
Stockholders’ Equity	14,669			3,101			10,550			(17,822		)	10,498
Total Liabilities and Stockholders’ Equity	$	19,414		$	16,728		$	17,370		$	(18,408	)	$	35,104
(a)	All significant intercompany transactions have been eliminated in consolidation.
Condensed Consolidating Statements of Cash Flows	'
	NRG ENERGY, INC. AND SUBSIDIARIES
	CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
	For the Nine Months Ended September 30, 2013
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Cash Flows from Operating Activities
	Net Cash Provided/(Used) by Operating Activities	1,334			135			(1,800		)	1,154			823
	Cash Flows from Investing Activities
	Intercompany loans to subsidiaries	(1,158		)	4			1,154			—			—
	Acquisition of businesses, net of cash acquired	—			(59		)	(315		)	—			(374		)
	Capital expenditures	(154		)	(1,388		)	(39		)	—			(1,581		)
	(Increase)/decrease in restricted cash, net	(7		)	(61		)	1			—			(67		)
	Increase in restricted cash — U.S. DOE projects	—			(18		)	(2		)	—			(20		)
	Decrease/(increase) in notes receivable	2			(16		)	(8		)	—			(22		)
	Investments in nuclear decommissioning trust fund securities	(369		)	—			—			—			(369		)
	Proceeds from sales of nuclear decommissioning trust fund securities	344			—			—			—			344
	Proceeds from renewable energy grants	—			52			—			—			52
	Proceeds from sale of assets, net of cash disposed of	13			—			—			—			13
	Other	7			(1		)	(13		)	—			(7		)
	Net Cash (Used)/Provided by Investing Activities	(1,322		)	(1,487		)	778			—			(2,031		)
	Cash Flows from Financing Activities
	Proceeds from intercompany loans	—			—			1,154			(1,154		)	—
	Payment of dividends to common and preferred stockholders	—			—			(113		)	—			(113		)
	Payment for treasury stock	—			—			(25		)	—			(25		)
	Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	(67		)	244			—			—			177
	Contributions from noncontrolling interest in subsidiaries	—			504			—			—			504
	Proceeds from issuance of long-term debt	—			1,120			485			—			1,605
	Proceeds from issuance of common stock	—			—			14			—			14
	Payment of debt issuance and hedging costs	—			(9		)	(34		)	—			(43		)
	Payments for short and long-term debt	—			(654		)	(214		)	—			(868		)
	Net Cash (Used)/Provided by Financing Activities	(67		)	1,205			1,267			(1,154		)	1,251
	Effect of exchange rate changes on cash and cash equivalents	—			(1		)	—			—			(1		)
	Net (Decrease)/Increase in Cash and Cash Equivalents	(55		)	(148		)	245			—			42
	Cash and Cash Equivalents at Beginning of Period	78			1,258			751			—			2,087
	Cash and Cash Equivalents at End of Period	$	23		$	1,110		$	996		$	—		$	2,129
	(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, 2012
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated Balance
								(Note Issuer)
		(In millions)
	Cash Flows from Operating Activities
	Net Cash Provided/(Used) by Operating Activities	1,942			177			(883		)	(178		)	1,058
	Cash Flows from Investing Activities
	Intercompany loans to subsidiaries	(1,686		)	416			—			1,270			—
	Acquisition of businesses, net of cash acquired	—			(17		)	(23		)	—			(40		)
	Capital expenditures	(183		)	(2,241		)	(50		)	—			(2,474		)
	Increase in restricted cash, net	(2		)	(94		)	—			—			(96		)
	Decrease in restricted cash — U.S. DOE projects	—			113			38			—			151
	Increase in notes receivable	—			(20		)	(2		)	—			(22		)
	Investments in nuclear decommissioning trust fund securities	(341		)	—			—			—			(341		)
	Proceeds from sales of nuclear decommissioning trust fund securities	316			—			—			—			316
	Proceeds from renewable energy grants	3			46			—			—			49
	Proceeds from sale of assets	133			—			4			—			137
	Other	13			(8		)	(14		)	—			(9		)
	Net Cash Used by Investing Activities	(1,747		)	(1,805		)	(47		)	1,270			(2,329		)
	Cash Flows from Financing Activities
	Proceeds from intercompany loans	—			—			1,270			(1,270		)	—
	Payment of dividends to preferred stockholders	(172		)	(6		)	—			178			—
Payment of intercompany dividends	—			—			(28		)	—			(28		)
Net payment for settlement of acquired derivatives that include financing elements	(65		)	—			—			—			(65		)
Proceeds from issuance of long-term debt	9			1,526			1,006			—			2,541
Sale proceeds and other contributions from noncontrolling interest in subsidiaries	—			316			—			—			316
Payment of debt issuance costs	—			(16		)	(14		)	—			(30		)
Payments for short and long-term debt	—			(51		)	(904		)	—			(955		)
Net Cash (Used)/Provided by Financing Activities	(228		)	1,769			1,330			(1,092		)	1,779
Effect of exchange rate changes on cash and cash equivalents	—			(3		)	—			—			(3		)
Net (Decrease)/Increase in Cash and Cash Equivalents	(33		)	138			400			—			505
Cash and Cash Equivalents at Beginning of Period	44			85			976			—			1,105
Cash and Cash Equivalents at End of Period	$	11		$	223		$	1,376		$	—		$	1,610
(a)	All significant intercompany transactions have been eliminated in consolidation.

Basis_of_Presentation_Basis_of1

Basis of Presentation Basis of Presentation (Details) (USD $)

Sep. 30, 2013

Dec. 31, 2012

Jul. 22, 2013

Sep. 30, 2013

Jul. 22, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Jul. 22, 2013

Sep. 30, 2013

Jul. 22, 2013

Jul. 22, 2013

In Millions, except Share data, unless otherwise specified

NRG

NRG Yield LLC

Class A Common Stock

Coal and dual-fired Facilites

Utility-scale Solar and Wind Facilities

Distributed Solar

Thermal

NRG

NRG

NRG Yield LLC

Public Shareholders

portfolio

NRG Yield Inc.

NRG Yield LLC

NRG Yield Inc.

NRG Yield LLC

NRG Yield LLC

NRG Yield Inc.

Class B Common Stock

NRG

NRG Yield Inc.

facility

facility

MW

MW

NRG Yield Inc.

Basis of Presentation

'

'

'

'

'

'

'

'

'

'

'

'

'

Sale of Stock, Number of Shares, Issued in Transaction

'

'

'

'

22,511,250

'

'

'

'

'

'

'

'

Sale of Stock, Price Per Share

'

'

'

'

$22

'

'

'

'

'

'

'

'

Proceeds from Issuance Initial Public Offering

'

'

'

'

$468

'

'

'

'

'

'

'

'

Administrative Fees, Amount Paid

'

'

'

'

$27

'

'

'

'

'

'

'

'

Common Stock, Shares, Outstanding

323,327,568

322,606,898

'

'

'

'

'

'

'

'

42,738,250

'

'

Sale of Stock, Percentage of Ownership after Transaction

'

'

65.50%

'

'

'

'

'

'

'

'

'

'

Sale of stock, Percentage of Ownership Sold

'

'

'

'

'

'

'

'

'

'

'

34.50%

'

Number of Facilities

'

'

'

'

'

3

8

'

'

'

'

'

'

Number of Portfolios of Distributed Solar Facilites

'

'

'

2

'

'

'

'

'

'

'

'

'

Generation Capacity (in MW)

'

'

'

'

'

'

'

1,324

123

'

'

'

'

Steam and Chilled Water Capacity (in MWt)

'

'

'

'

'

'

'

'

1,098

'

'

'

'

Common Stock, Voting Interest

'

'

'

'

'

'

'

'

'

65.50%

'

'

34.50%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Noncontrolling Interest [Abstract]	'	'	'	'
Noncontrolling interest	'	'	$518	'
Contributions from noncontrolling interest	'	'	289	'
Comprehensive income attributable to noncontrolling interest	18	9	26	18
Noncontrolling interest	833	'	833	'
Other Cash Flow Information Disclosure [Abstract]	'	'	'	'
Gain (Loss) on Sale of Interest in Projects	'	'	221	'
Capital expenditures accrued and unpaid	$127	'	'	'

Business_Acquisitions_and_Disp2

Business Acquisitions and Dispositions (Details)

0 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

1 Months Ended

9 Months Ended

0 Months Ended

Jul. 19, 2012

Sep. 30, 2013

Sep. 30, 2012

Jul. 17, 2012

Jan. 18, 2012

Jan. 18, 2012

Jul. 17, 2012

Jul. 17, 2012

Jul. 17, 2012

Oct. 18, 2013

Aug. 07, 2013

Feb. 14, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 14, 2012

Jul. 17, 2012

Oct. 18, 2013

Oct. 18, 2013

USD ($)

USD ($)

USD ($)

USD ($)

NRG Solar AC Holdings LLC

Sale of Interest in Agua Caliente

Kraftwerke Schkopau

Kraftwerke Schkopau Betriebsgesllshaft mbH

Schkopau

Edison Mission Energy

Gregory

GenOn Energy

GenOn Energy

GenOn Energy

GenOn Energy

Foreign Currency Swap

Subsequent Event

Subsequent Event

MW

USD ($)

MW

MW

USD ($)

USD ($)

USD ($)

USD ($)

USD ($)

EUR (€)

Edison Mission Energy

Common Stock

MW

MW

USD ($)

Edison Mission Energy

USD ($)

Business Acquisition

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Generation Capacity (in MW)

'

'

'

'

'

'

'

'

900

8,000

388

'

'

'

21,440

'

'

'

Payments to Acquire Business, Estimated

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$2,600,000,000

'

Business Acquisition, Equity Interest Issued or Issuable, Number of Shares

'

'

'

'

'

'

'

'

'

'

'

93,900,000

'

'

'

'

'

12,671,977

Business Acquisition, Equity Interest Issued or Issuable, Value Assigned

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

350,000,000

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents

'

'

'

'

'

'

'

'

'

'

32,000,000

'

'

'

983,000,000

'

1,100,000,000

'

Business Combination, Estimated Consideration Transferred, Estimated Liabilities Incurred

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

700,000,000

'

Business Acquisition, Purchase Price Allocation, Noncurrent Liabilities, Long-term Debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,203,000,000

'

1,500,000,000

'

Environmental Capital Expenditures, Estimated

'

530,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

350,000,000

'

Payments to Acquire Business, Fee Contingently Receivable

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

65,000,000

'

Payments to Acquire Businesses, Net of Cash Acquired

'

374,000,000

40,000,000

'

'

'

'

'

'

'

245,000,000

'

'

'

'

'

'

'

Steam Capacity (in MWt)

'

'

'

'

'

'

'

'

'

'

160

'

'

'

'

'

'

'

Business Acquisition, Cost of Acquired Entity, Equity Interests Issued and Issuable

'

'

'

'

'

'

'

'

'

'

'

2,188,000,000

'

'

'

'

'

'

BusinessAcquisitionEquityInterestIssuedOrIssuableExchangeRatio

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12.16%

'

'

'

Business Acquisition, Purchase Price, Percentage of Outstanding Common Shares

'

'

'

'

'

'

'

'

'

'

'

'

29.00%

'

'

'

'

'

Business Acquisition, Purchase Price Allocation, Other Assets

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,385,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Assets

'

'

'

'

'

'

'

'

'

'

'

'

'

-18,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Other Assets, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,367,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Property, Plant and Equipment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,936,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment

'

'

'

'

'

'

'

'

'

'

'

'

'

-27,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Property, Plant and Equipment, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,909,000,000

'

'

'

Business Acquisition Purchase Price Allocation, Derivative Assets

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,157,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Deferred Taxes Asset (Liability), Net, Noncurrent

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,265,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Taxes Asset (Liability), Net, Noncurrent

'

'

'

'

'

'

'

'

'

'

'

'

'

21,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Deferred Taxes Asset (Liability), Net, Noncurrent, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,286,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Assets Acquired

'

'

'

'

'

'

'

'

'

'

'

'

'

'

9,726,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets

'

'

'

'

'

'

'

'

'

'

'

'

'

-24,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Assets Acquired, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

9,702,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Other Liabilities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,312,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current and Noncurrent Liabilities

'

'

'

'

'

'

'

'

'

'

'

'

'

-7,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Other Liabilities, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,305,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Out of Market Contracts and Leases

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,064,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Out of Market Contracts and Leases

'

'

'

'

'

'

'

'

'

'

'

'

'

15,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Out of Market Contracts and Leases, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,079,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Derivative Liabilities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

399,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Liabilities Longterm Debt

'

'

'

'

'

'

'

'

'

'

'

'

'

3,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Noncurrent Liabilities, Long-term Debt, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,206,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Liabilities Assumed

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,978,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities

'

'

'

'

'

'

'

'

'

'

'

'

'

11,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Liabilities Assumed, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,989,000,000

'

'

'

Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,748,000,000

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Net Assets Acquired

'

'

'

'

'

'

'

'

'

'

'

'

'

-35,000,000

'

'

'

'

Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,713,000,000

'

'

'

Business Combination, Bargain Purchase, Gain Recognized, Amount

'

'

'

'

'

'

'

'

'

'

'

'

560,000,000

'

'

'

'

'

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Bargain Purchase, Gain Recognized, Amount

'

'

'

'

'

'

'

'

'

'

'

'

'

-35,000,000

'

'

'

'

Business Combination, Bargain Purchase, Gain Recognized, Amount, Adjusted

'

'

'

'

'

'

'

'

'

'

'

'

525,000,000

'

'

'

'

'

Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners

'

'

'

'

49.00%

49.00%

'

'

'

'

'

'

'

'

'

'

'

'

Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Sale of Interest by Parent

'

'

'

'

'

122,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Investment Owned, Percent of Net Assets

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

Equity Method Investment, Ownership Percentage

'

'

'

'

'

'

41.90%

44.40%

'

'

'

'

'

'

'

'

'

'

Power Generation, Participation (in MW)

'

'

'

400

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Foreign Curreny Swap Contract

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

141,000,000

'

'

Long Lived Assets Held-for-sale, Proceeds from Sale

174,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain (Loss) on Derivative Instruments, Net, Pretax

4,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Assets Held-for-sale, Long Lived

'

'

'

$38,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions	'		'
Long-term debt, including current portion	$16,699		$15,866
Carrying Amount	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions	'		'
Notes receivable	107	[1]	88	[1]
Long-term debt, including current portion	16,699		15,866
Fair Value	'		'
Fair Value, Balance Sheet Grouping, Financial Statement Captions	'		'
Notes receivable	107	[1]	88	[1]
Long-term debt, including current portion	$17,061		$16,492
[1]	Includes the current portion of notes receivable which is recorded in prepayments and other current assets on the Company's consolidated balance sheets

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments (Details 2) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	$1,895		$3,306
Derivative liabilities	1,436		2,481
Commodity contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	1,884		3,303
Derivative liabilities	1,354		2,338
Interest rate contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	11		3
Derivative liabilities	82		143
Fair Value, Measurements, Recurring | Level 1	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Debt securities	0		0
Other	37	[1]	44	[1]
Total assets	807		1,778
Total liabilities	344		1,144
Fair Value, Measurements, Recurring | Level 1 | Commodity contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	436		1,457
Derivative liabilities	344		1,144
Fair Value, Measurements, Recurring | Level 1 | Interest rate contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
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 Basis	'		'
Trust fund investments	2		10
Fair Value, Measurements, Recurring | Level 1 | U.S. government and federal agency obligations	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	51		34
Fair Value, Measurements, Recurring | Level 1 | Federal agency mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 1 | Commercial mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 1 | Corporate debt securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 1 | Equity securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	281		233
Fair Value, Measurements, Recurring | Level 1 | Foreign government fixed income securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 2	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Debt securities	0		0
Other	0	[1]	0	[1]
Total assets	1,484		1,864
Total liabilities	974		1,190
Fair Value, Measurements, Recurring | Level 2 | Commodity contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	1,337		1,711
Derivative liabilities	892		1,047
Fair Value, Measurements, Recurring | Level 2 | Interest rate contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	11		3
Derivative liabilities	82		143
Fair Value, Measurements, Recurring | Level 2 | Cash and cash equivalents	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 2 | U.S. government and federal agency obligations	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	4		0
Fair Value, Measurements, Recurring | Level 2 | Federal agency mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	58		59
Fair Value, Measurements, Recurring | Level 2 | Commercial mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	12		9
Fair Value, Measurements, Recurring | Level 2 | Corporate debt securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	60		80
Fair Value, Measurements, Recurring | Level 2 | Equity securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 2 | Foreign government fixed income securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	2		2
Fair Value, Measurements, Recurring | Level 3	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Debt securities	15		12
Other	0	[1]	0	[1]
Total assets	181		194
Total liabilities	118		147
Fair Value, Measurements, Recurring | Level 3 | Commodity contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	111		135
Derivative liabilities	118		147
Fair Value, Measurements, Recurring | Level 3 | Interest rate contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
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 Basis	'		'
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 Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 3 | Federal agency mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 3 | Commercial mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 3 | Corporate debt securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Level 3 | Equity securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	55		47
Fair Value, Measurements, Recurring | Level 3 | Foreign government fixed income securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	0		0
Fair Value, Measurements, Recurring | Fair Value	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Debt securities	15		12
Other	37	[1]	44	[1]
Total assets	2,472		3,836
Total liabilities	1,436		2,481
Fair Value, Measurements, Recurring | Fair Value | Commodity contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	1,884		3,303
Derivative liabilities	1,354		2,338
Fair Value, Measurements, Recurring | Fair Value | Interest rate contracts	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Derivative Assets	11		3
Derivative liabilities	82		143
Fair Value, Measurements, Recurring | Fair Value | Cash and cash equivalents	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	2		10
Fair Value, Measurements, Recurring | Fair Value | U.S. government and federal agency obligations	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	55		34
Fair Value, Measurements, Recurring | Fair Value | Federal agency mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	58		59
Fair Value, Measurements, Recurring | Fair Value | Commercial mortgage-backed securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	12		9
Fair Value, Measurements, Recurring | Fair Value | Corporate debt securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	60		80
Fair Value, Measurements, Recurring | Fair Value | Equity securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	336		280
Fair Value, Measurements, Recurring | Fair Value | Foreign government fixed income securities	'		'
Fair Value Assets and Liabilities, Measured on Recurring Basis	'		'
Trust fund investments	$2		$2
[1]	Primarily consists of mutual funds held in rabbi trusts for non-qualified deferred compensation plans for certain former employees.

Fair_Value_of_Financial_Instru4

Fair Value of Financial Instruments (Details 3) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Fair Value Asset and Liabilities, Measured on Recurring Basis Unobservable Input, Changes	'		'		'		'
No transfers during the three and six months ended June 30, 2013 and 2013 (Level 1 to Level 2)	$0		$0		$0		$0
No transfers during the three and six months ended June 30, 2013 and 2013 (Level 2 to Level 1)	0		0		0		0
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements	'		'		'		'
Beginning balance	53,000,000		223,000,000		47,000,000		57,000,000
Total gains/(losses) - realized/unrealized:	'		'		'		'
Included in earnings	14,000,000		-9,000,000		-4,000,000		-3,000,000
Included in OCI	0		2,000,000		3,000,000		4,000,000
Included in nuclear decommissioning obligations	5,000,000		3,000,000		7,000,000		3,000,000
Purchases	4,000,000		-109,000,000		-2,000,000		0
Transfers into Level 3	-36,000,000	[1]	-31,000,000	[1]	-9,000,000	[1]	4,000,000	[1]
Transfers out of Level 3	23,000,000	[1]	-20,000,000	[1]	21,000,000	[1]	-6,000,000	[1]
Ending balance	63,000,000		59,000,000		63,000,000		59,000,000
Gains/(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 period end	-7,000,000		-5,000,000		-4,000,000		1,000,000
Debt Securities	'		'		'		'
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements	'		'		'		'
Beginning balance	15,000,000		9,000,000		12,000,000		7,000,000
Total gains/(losses) - realized/unrealized:	'		'		'		'
Included in earnings	0		0		0		0
Included in OCI	0		2,000,000		3,000,000		4,000,000
Included in nuclear decommissioning obligations	0		0		0		0
Purchases	0		0		0		0
Transfers into Level 3	0	[1]	0	[1]	0	[1]	0	[1]
Transfers out of Level 3	0	[1]	0	[1]	0	[1]	0	[1]
Ending balance	15,000,000		11,000,000		15,000,000		11,000,000
Gains/(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 period end	0		0		0		0
Trust Fund Investments	'		'		'		'
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements	'		'		'		'
Beginning balance	50,000,000		43,000,000		47,000,000		42,000,000
Total gains/(losses) - realized/unrealized:	'		'		'		'
Included in earnings	0		0		0		0
Included in OCI	0		0		0		0
Included in nuclear decommissioning obligations	5,000,000		3,000,000		7,000,000		3,000,000
Purchases	0		0		1,000,000		1,000,000
Transfers into Level 3	0	[1]	0	[1]	0	[1]	0	[1]
Transfers out of Level 3	0	[1]	0	[1]	0	[1]	0	[1]
Ending balance	55,000,000		46,000,000		55,000,000		46,000,000
Gains/(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 period end	0		0		0		0
Derivatives	'		'		'		'
Reconciliation of the beginning and ending balances for financial instruments that are recognized at fair value in the consolidated financial statements	'		'		'		'
Beginning balance	-12,000,000	[2]	171,000,000	[2]	-12,000,000	[2]	8,000,000	[2]
Total gains/(losses) - realized/unrealized:	'		'		'		'
Included in earnings	14,000,000	[2]	-9,000,000	[2]	-4,000,000	[2]	-3,000,000	[2]
Included in OCI	0	[2]	0	[2]	0	[2]	0	[2]
Included in nuclear decommissioning obligations	0	[2]	0	[2]	0	[2]	0	[2]
Purchases	4,000,000	[2]	-109,000,000	[2]	-3,000,000	[2]	-1,000,000	[2]
Transfers into Level 3	-36,000,000	[1],[2]	-31,000,000	[1],[2]	-9,000,000	[1],[2]	4,000,000	[1],[2]
Transfers out of Level 3	23,000,000	[1],[2]	-20,000,000	[1],[2]	21,000,000	[1],[2]	-6,000,000	[1],[2]
Ending balance	-7,000,000	[2]	2,000,000	[2]	-7,000,000	[2]	2,000,000	[2]
Gains/(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 period end	($7,000,000)	[2]	($5,000,000)	[2]	($4,000,000)	[2]	$1,000,000	[2]
[1]	Transfers in/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.
[2]	Consists of derivative assets and liabilities, net.

Fair_Value_of_Financial_Instru5

Fair Value of Financial Instruments (Details 4) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012
Concentration of Credit Risk	'		'
Total derivative assets valued with prices provied by models and other valuation techniques (as a percent)	6.00%		'
Total derivative liabilities valued with prices provied by models and other valuation techniques (as a percent)	8.00%		'
Increase in fair value as a result of the credit reserve	($1)		$9
Increase in fair value as a result of the credit reserve, portion recorded in OCI	-1		-4
Increase in fair value as a result of the credit reserve, portion recorded in operating revenue and cost of operations	2		-5
Counterparty credit exposure to a portion of the Company's counterparties	975		'
Collateral held (cash and letters of credit) against counterparty credit exposure to a portion of the Company's counterparties	44		'
Net counterparty credit exposure to a portion of the Company's counterparties	931		'
Company's exposure before collateral is expected to roll off by the end of 2014 (as a percent)	85.00%		'
Net Exposure (as a percent)	100.00%	[1]	'
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	316		'
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	2,300		'
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)	96.00%	[1]	'
Non-rated	'		'
Concentration of Credit Risk	'		'
Net Exposure (as a percent)	4.00%	[1],[2]	'
Financial institutions	'		'
Concentration of Credit Risk	'		'
Net Exposure (as a percent)	58.00%	[1]	'
Utilities, energy merchants, marketers and other	'		'
Concentration of Credit Risk	'		'
Net Exposure (as a percent)	34.00%	[1]	'
ISOs	'		'
Concentration of Credit Risk	'		'
Net Exposure (as a percent)	6.00%	[1]	'
Coal and emissions	'		'
Concentration of Credit Risk	'		'
Net Exposure (as a percent)	2.00%	[1]	'
NRG Yield, Inc.	'		'
Concentration of Credit Risk	'		'
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	$649		'
[1]	Counterparty credit exposure excludes uranium and coal transportation contracts because of the unavailability of market prices.
[2]	For non-rated counterparties, a significant portion are related to ISO and municipal public power entities, which are considered investment grade equivalent ratings based on NRG's internal credit ratings.

Nuclear_Decommissioning_Trust_2

Nuclear Decommissioning Trust Fund (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	$524,000,000	'	$473,000,000
Unrealized Gains	192,000,000	'	151,000,000	[1]
Unrealized Losses	3,000,000	'	0
Proceeds from sales of available-for-sale securities and the related realized gains and losses	'	'	'
Realized gains	10,000,000	8,000,000	'
Proceeds from sale of securities	7,000,000	5,000,000	'
Proceeds from sale of securities	344,000,000	316,000,000	'
Cash and cash equivalents	'	'	'
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	2,000,000	'	10,000,000
Unrealized Gains	0	'	0	[1]
Unrealized Losses	0	'	'
Weighted-average Maturities (In years)	0	'	0
U.S. government and federal agency obligations	'	'	'
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	54,000,000	'	33,000,000
Unrealized Gains	2,000,000	'	2,000,000	[1]
Unrealized Losses	1,000,000	'	'
Weighted-average Maturities (In years)	9	'	10
Federal agency mortgage-backed securities	'	'	'
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	58,000,000	'	59,000,000
Unrealized Gains	1,000,000	'	2,000,000	[1]
Unrealized Losses	1,000,000	'	'
Weighted-average Maturities (In years)	24	'	23
Commercial mortgage-backed securities	'	'	'
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	12,000,000	'	9,000,000
Unrealized Gains	0	'	0	[1]
Unrealized Losses	0	'	'
Weighted-average Maturities (In years)	29	'	30
Corporate debt securities	'	'	'
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	60,000,000	'	80,000,000
Unrealized Gains	2,000,000	'	4,000,000	[1]
Unrealized Losses	1,000,000	'	'
Weighted-average Maturities (In years)	9	'	11
Equity securities	'	'	'
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	336,000,000	'	280,000,000
Unrealized Gains	187,000,000	'	143,000,000	[1]
Unrealized Losses	'	'	'
Weighted-average Maturities (In years)	0	'	0
Foreign government fixed income securities	'	'	'
Nuclear decommissioning trust fund disclosure	'	'	'
Fair Value	2,000,000	'	2,000,000
Unrealized Gains	$0	'	$0	[1]
Weighted-average Maturities (In years)	9	'	6
[1]	There were no unrealized losses as of December 31, 2012.

Accounting_for_Derivative_Inst2

Accounting for Derivative Instruments and Hedging Activities (Details) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value of Derivative Instrument	'	'
Derivative Assets	$1,895	$3,306
Derivative Liabilities	1,436	2,481
Derivatives Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	8	3
Derivative Liabilities	77	129
Derivatives Not Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	1,887	3,303
Derivative Liabilities	1,359	2,352
Interest rate contracts current | Derivatives Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	0	0
Derivative Liabilities	27	29
Interest rate contracts current | Derivatives Not Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	0	0
Derivative Liabilities	5	7
Interest rate contracts long-term | Derivatives Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	8	3
Derivative Liabilities	47	96
Interest rate contracts long-term | Derivatives Not Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	3	0
Derivative Liabilities	3	11
Commodity contracts current | Derivatives Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	0	0
Derivative Liabilities	2	3
Commodity contracts current | Derivatives Not Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	1,389	2,644
Derivative Liabilities	1,030	1,942
Commodity contracts long-term | Derivatives Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	0	0
Derivative Liabilities	1	1
Commodity contracts long-term | Derivatives Not Designated as Cash Flow Hedges	'	'
Fair Value of Derivative Instrument	'	'
Derivative Assets	495	659
Derivative Liabilities	321	392
Short Ton | Emissions	'	'
Volumetric Underlying Derivative Transactions	'	'
Underlying, Derivative	-1,000,000	-1,000,000
Short Ton | Coal	'	'
Volumetric Underlying Derivative Transactions	'	'
Underlying, Derivative	42,000,000	37,000,000
MMbtu | Natural Gas	'	'
Volumetric Underlying Derivative Transactions	'	'
Underlying, Derivative	-215,000,000	-413,000,000
Barrel | Oil	'	'
Volumetric Underlying Derivative Transactions	'	'
Underlying, Derivative	0	1,000,000
MWh | Power	'	'
Volumetric Underlying Derivative Transactions	'	'
Underlying, Derivative	-16,000,000	-14,000,000
Dollars | Interest	'	'
Volumetric Underlying Derivative Transactions	'	'
Derivative, Notional Amount	$1,520	$2,612

Accounting_for_Derivative_Inst3

Accounting for Derivative Instruments and Hedging Activities (Details 2) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid	'	'
Gross Amount of Recognized Derivative Assets	$1,895	$3,306
Cash Collateral (Held)	-122	-271
Gross Amounts of Recognized Derivative Liabilities	-1,436	-2,481
Cash Collateral Posted	288	229
Gross Amounts of Recognized Assets / Liabilities	459	825
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	-130	-346
Net Amount	329	479
Commodity contracts	'	'
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid	'	'
Gross Amount of Recognized Derivative Assets	1,884	3,303
Derivative Instruments	-1,151	-2,024
Cash Collateral (Held)	-195	-374
Net Amount	538	905
Gross Amounts of Recognized Derivative Liabilities	-1,354	-2,338
Derivative Instruments	1,151	2,024
Cash Collateral Posted	65	28
Net Amount	-138	-286
Gross Amounts of Recognized Assets / Liabilities	530	965
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	-130	-346
Net Amount	400	619
Interest rate contracts	'	'
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid	'	'
Gross Amount of Recognized Derivative Assets	11	3
Derivative Instruments	-6	0
Cash Collateral (Held)	0	0
Net Amount	5	3
Gross Amounts of Recognized Derivative Liabilities	-82	-143
Derivative Instruments	6	0
Cash Collateral Posted	0	0
Net Amount	-76	-143
Gross Amounts of Recognized Assets / Liabilities	-71	-140
Derivative Instruments	0	0
Cash Collateral (Held) / Posted	0	0
Net Amount	($71)	($140)

Accounting_for_Derivative_Inst4

Accounting for Derivative Instruments and Hedging Activities (Details 3) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax	'	'	'	'
Accumulated OCI beginning balance	($7)	$43	($31)	$132
Net Income/(Loss)	143	8	-47	61
Mark-to-market of cash flow hedge accounting contracts	-3	-16	40	-37
Accumulated OCI ending balance, net of tax	-23	0	-23	0
Gains/(losses) expected to be realized from OCI during the next 12 months, net of tax	2	66	2	66
Gains/(losses) recognized in income from the ineffective portion of cash flow hedges	1	0	0	-51
Accumulated OCI ending balance, tax	13	12	13	12
Gains/(losses) expected to be realized from OCI during the next 12 months, tax	1	38	1	38
Unrealized mark-to-market results	'	'	'	'
Reversal of previously recognized unrealized losses/(gains) on settled positions related to economic hedges	-48	-85	-80	-160
Reversal of loss positions acquired as part of the acquisition	-82	-15	-269	5
Net unrealized gains/(losses) on open positions related to economic hedges	76	-159	131	-78
Losses on ineffectiveness associated with open positions treated as cash flow hedges	1	0	0	-51
Total unrealized mark-to-market gains/(losses) for economic hedging activities	-53	-259	-218	-284
Reversal of previously recognized unrealized (gains) losses on settled positions related to trading activity	-13	-15	-42	-45
Reversal of Previously Unrecognized Unrealized Gain Loss Acquired as Part of Acquisition Trading Activity	-2	0	-2	0
Net unrealized gains on open positions related to trading activity	26	-3	0	33
Total unrealized mark-to-market gains for trading activity	11	-18	-44	-12
Impact of derivative instruments on statement of operations	'	'	'	'
Total unrealized gains/(losses)	-42	-277	-262	-296
Credit Risk Related Contingent Features	'	'	'	'
Collateral required for contracts with adequate assurance clauses in net liability positions	103	'	103	'
Collateral required for contracts with credit rating contingent features	39	'	39	'
Collateral due on net liability position that has not been called by a certain marginable agreement counterparty	15	'	15	'
Commodity contracts	'	'	'	'
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax	'	'	'	'
Accumulated OCI beginning balance	24	111	41	188
Mark-to-market of cash flow hedge accounting contracts	1	-1	7	-2
Accumulated OCI ending balance, net of tax	10	80	10	80
Gains/(losses) expected to be realized from OCI during the next 12 months, net of tax	11	77	11	77
Gains/(losses) recognized in income from the ineffective portion of cash flow hedges	1	0	0	-51
Impact of derivative instruments on statement of operations	'	'	'	'
Total unrealized gains/(losses)	-42	-277	-262	-296
Commodity contracts | Gains (losses) included in operating revenues	'	'	'	'
Impact of derivative instruments on statement of operations	'	'	'	'
Total unrealized gains/(losses)	-64	-395	-404	-470
Commodity contracts | Gains (losses) included in cost of operations	'	'	'	'
Impact of derivative instruments on statement of operations	'	'	'	'
Total unrealized gains/(losses)	22	118	142	174
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	-31	-68	-72	-56
Mark-to-market of cash flow hedge accounting contracts	-4	-15	33	-35
Accumulated OCI ending balance, net of tax	-33	-80	-33	-80
Gains/(losses) expected to be realized from OCI during the next 12 months, net of tax	-9	-11	-9	-11
Gains/(losses) recognized in income from the ineffective portion of cash flow hedges	0	0	0	0
Impact of derivative instruments on statement of operations	'	'	'	'
Total unrealized gains/(losses)	4	0	10	-12
CVSR | Interest rate contracts	'	'	'	'
Discontinuation of cash flow hedges	'	'	'	'
Loss previously deferred in OCI recognized in earnings resulting from discontinued cash flow hedge accounting	'	'	5	'
Alpine | Interest rate contracts	'	'	'	'
Discontinuation of cash flow hedges	'	'	'	'
Loss previously deferred in OCI recognized in earnings resulting from discontinued cash flow hedge accounting	'	'	4	4
Reclassification out of Accumulated Other Comprehensive Income	'	'	'	'
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax	'	'	'	'
Net Income/(Loss)	-13	-27	-32	-95
Reclassification out of Accumulated Other Comprehensive Income | Commodity contracts	'	'	'	'
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax	'	'	'	'
Net Income/(Loss)	-15	-30	-38	-106
Reclassification out of Accumulated Other Comprehensive Income | Interest rate contracts	'	'	'	'
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax	'	'	'	'
Net Income/(Loss)	$2	$3	$6	$11

Debt_and_Capital_Leases_Debt_a1

Debt and Capital Leases Debt and Capital Leases (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

2 Months Ended

2 Months Ended

2 Months Ended

9 Months Ended

9 Months Ended

1 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

1 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

1 Months Ended

1 Months Ended

1 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

1 Months Ended

1 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

In Millions, unless otherwise specified

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Mar. 31, 2013

Feb. 27, 2013

Feb. 27, 2013

Sep. 30, 2013

Dec. 31, 2012

Feb. 27, 2013

Sep. 30, 2013

Dec. 31, 2012

Feb. 27, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Jun. 04, 2013

Jun. 30, 2013

Mar. 31, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Mar. 31, 2013

Mar. 16, 2012

Mar. 31, 2013

Sep. 30, 2013

Jan. 15, 2013

Mar. 16, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Mar. 31, 2013

Sep. 30, 2013

Mar. 28, 2013

Sep. 30, 2013

Dec. 31, 2012

Mar. 31, 2013

Sep. 30, 2013

Mar. 28, 2013

Mar. 31, 2013

Sep. 30, 2013

Mar. 28, 2013

Mar. 31, 2013

Mar. 28, 2013

Sep. 30, 2013

Mar. 28, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2013

Sep. 30, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Jun. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Jun. 30, 2013

Jun. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Recourse Debt

Recourse Debt

Non Recourse Debt

Non Recourse Debt

Senior Notes Repurchases

Senior Notes Repurchases

Senior notes, due 2018

Senior notes, due 2018

Senior notes, due 2018

8.500% Senior notes, due 2019

8.500% Senior notes, due 2019

8.500% Senior notes, due 2019

Senior notes, due 2020

Senior notes, due 2020

Senior notes, due 2020

7.625% Senior notes, due 2019

7.625% Senior notes, due 2019

Senior notes, due 2021

Senior notes, due 2021

Senior notes, due 2023

Senior notes, due 2023

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Term loan facility, due 2018

Indian River Power LLC, tax-exempt bonds, due 2040 and 2045

Indian River Power LLC, tax-exempt bonds, due 2040 and 2045

Indian River Power LLC, tax-exempt bonds, due 2040

Indian River Power LLC, tax-exempt bonds, due 2045

Dunkirk Power LLC, tax-exempt bonds, due 2042

Dunkirk Power LLC, tax-exempt bonds, due 2042

Fort Bend County, tax-exempt bonds, due 2038 and 2042

Fort Bend County, tax-exempt bonds, due 2038 and 2042

GenOn senior notes, due 2014

GenOn senior notes, due 2014

GenOn senior notes, due 2014

GenOn senior notes, due 2014

GenOn senior notes, due 2017

GenOn senior notes, due 2017

GenOn senior notes, due 2018

GenOn senior notes, due 2018

GenOn senior notes, due 2020

GenOn senior notes, due 2020

GenOn Americas Generation senior notes, due in 2021

GenOn Americas Generation senior notes, due in 2021

GenOn Americas Generation senior notes, due in 2031

GenOn Americas Generation senior notes, due in 2031

GenOn Marsh Landing term loans, due 2017 and 2023

GenOn Marsh Landing term loans, due 2017 and 2023

GenOn Marsh Landing term loan, due 2017

GenOn Marsh Landing term loan, due 2017

GenOn Marsh Landing term loan, due 2023

GenOn Marsh Landing term loan, due 2023

CVSR - High Plains Ranch II LLC, due 2037

CVSR - High Plains Ranch II LLC, due 2037

NRG West Holdings LLC, term loan, due 2023

NRG West Holdings LLC, term loan, due 2023

NRG West Holdings LLC, term loan, due 2023

Agua Caliente Solar LLC, due 2037

Agua Caliente Solar LLC, due 2037

Ivanpah Financing, due 2014 and 2038

Ivanpah Financing, due 2014 and 2038

South Trent Wind LLC, financing agreement, due 2020

South Trent Wind LLC, financing agreement, due 2020

South Trent Wind LLC, financing agreement, due 2020

NRG Peaker Finance Co. LLC, bonds, due 2019

NRG Peaker Finance Co. LLC, bonds, due 2019

NRG Peaker Finance Co. LLC, bonds, due 2019

NRG Energy Center Minneapolis LLC, senior secured notes, due 2013, 2017, and 2025

NRG Energy Center Minneapolis LLC, senior secured notes, due 2013, 2017, and 2025

NRG Energy Center Minneapolis LLC Senior Secured Notes, due 2013

NRG Energy Center Minneapolis LLC Senior Secured Notes, due 2017

NRG Energy Center Minneapolis LLC Senior Secured Notes, due 2025

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013 and 2022

NRG Solar Alpine LLC, due 2013

NRG Solar Alpine LLC, due 2013

NRG Solar Alpine LLC, due 2022

NRG Solar Alpine LLC, due 2022

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

NRG Solar Borrego LLC, due 2024 and 2038

Borrego Financing Agreement, due 2024

Borrego Financing Agreement, due 2024

Borrego Financing Agreement, due 2038

NRG Solar Avra Valley LLC

NRG Solar Avra Valley LLC

NRG Solar Avra Valley LLC

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility

High Desert Facility, due 2013

High Desert Facility, due 2013

High Desert Facility, due 2023

High Desert Facility, due 2023

High Desert Facility, due 2033

Kansas South Facility

Kansas South Facility

Kansas South Facility

Kansas South Facility

Kansas South Facility

Kansas South Facility

Kansas South Facility

Kansas South Facility

Kansas South Facility, due 2013

Kansas South Facility, due 2031

Other (Non-recourse debt)

Other (Non-recourse debt)

Chalk Point capital lease, due 2015

Chalk Point capital lease, due 2015

Other (Capital leases)

Other (Capital leases)

NRG Repowering Holdings LLC Credit Facility

Kansas South

TA - High Desert LLC

Marsh Landing

NRG Yield Inc.

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Term Loan

Term Loan

Term Loan

Term Loan

Term Loan

Term Loan

Term Loan

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Letters of Credit

Term Loan

Construction Loan

Construction Loan

Cash Grant Loan

Cash Grant Loan

Cash Grant Loan

Cash Grant Loan

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Interest Rate Swaps

Interest Rate Swaps

Interest Rate Swaps

Non Recourse Debt

Non Recourse Debt

Letters of Credit

Letters of Credit

Letters of Credit

Term Loan

Term Loan

Term Loan

Term Loan

Term Loan

Fixed Rate Notes

Fixed Rate Notes

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Revolving Credit Facility

Revolving Credit Facility

Revolving Credit Facility

Fixed Rate Notes

Floating Rate Notes

Floating Rate Notes

Bridge Loan

Bridge Loan

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Letters of Credit

Term Loan

Term Loan

Cash Grant Bridge Loan

Cash Grant Bridge Loan

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Non Recourse Debt

Letters of Credit

MW

MW

Letters of Credit

Revolving Credit Facility

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

interest_rate_derivative

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

LIBOR

Debt and Capital Leases

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Long-term debt

$16,699

'

$16,699

'

$15,866

$8,091

$7,818

$8,608

$8,048

'

'

'

$1,130

$1,200

'

$601

$693

'

$1,063

$1,100

$800

$800

$1,128

$1,128

$990

$990

$2,006

$1,573

'

'

'

'

'

'

'

'

'

'

'

$247

$247

'

'

$59

$59

$67

$28

'

'

$0

$617

$787

$800

$785

$801

$624

$631

$504

$509

$435

$437

$500

$390

'

'

'

'

$1,104

$786

$475

$350

'

$764

$640

$1,561

$1,437

$69

$72

'

$176

$173

'

$129

$137

'

'

'

$223

$2

'

$161

'

'

'

$62

'

'

'

'

'

'

'

'

'

$79

$0

'

'

'

'

$34

'

'

'

$45

'

'

'

'

$64

$66

'

$82

$82

$0

'

'

'

$53

$7

'

$22

'

'

'

'

'

'

$59

$59

$0

'

$38

'

$21

'

'

'

$188

$200

'

'

'

'

'

'

'

'

'

Chalk Point capital lease, due 2015

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

'

'

'

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'

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'

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'

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'

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'

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'

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'

'

'

'

'

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'

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'

'

'

'

'

'

'

'

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'

'

'

'

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'

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'

'

'

'

'

'

'

'

'

'

'

'

11

14

3

3

'

'

'

'

'

Subtotal

16,713

'

16,713

'

15,883

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Less current maturities

911

'

911

'

147

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

'

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'

'

'

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'

'

'

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'

'

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'

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'

'

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'

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'

'

'

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'

'

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'

'

'

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'

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'

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'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total long-term debt and capital leases

15,802

'

15,802

'

15,736

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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'

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'

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'

'

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'

'

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'

'

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'

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'

'

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'

'

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'

'

'

'

'

'

'

'

Interest rate, stated rate

'

'

'

'

'

'

'

'

'

'

'

'

7.63%

[1]

'

'

8.50%

[1]

'

'

8.25%

[1]

'

7.63%

[1]

'

7.88%

[1]

'

6.63%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6.00%

[1]

5.38%

[1]

5.88%

[1]

'

4.75%

[1]

'

'

'

7.63%

[1]

'

7.88%

[1]

'

9.50%

[1]

'

9.88%

[1]

'

8.50%

[1]

'

9.13%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7.31%

[1]

'

5.95%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.65%

'

'

5.65%

[1]

'

'

'

'

'

'

'

'

'

5.15%

'

'

'

'

'

'

'

'

5.15%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate, variable basis

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'LIBOR

[1]

'

'

'LIBOR

'

'

'LIBOR

'

'

'LIBOR

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'LIBOR

[1]

'

'LIBOR

[1]

'

'

'

'LIBOR

[1]

'

'

'

'

'

'

'LIBOR

[1]

'

'

'LIBOR

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'LIBOR

[1]

'

'LIBOR

[1]

'

'3 month LIBOR

'

'

'

'

'

'

'

'3 month LIBOR

'

'

'

'

'

'

'LIBOR

[1]

'

'

'LIBOR

[1]

'

'

'

'

'

'3 month LIBOR

'

'

'

'3 month LIBOR

'

'3 month LIBOR

'

'LIBOR

[1]

'

'LIBOR

[1]

'

'

'

'

'

'

'6 month LIBOR

'

'1 month LIBOR

'

'LIBOR

[1]

'LIBOR

[1]

'

'

'

'

'

'

'

'

'

'

'

Interest rate, basis spread on variable rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.50%

[1]

'

'

2.25%

'

'

'

'

'

2.00%

2.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.50%

[1]

'

2.75%

[1]

'

'

'

'

'

'

'

'

'

'

'

2.63%

[1]

'

'

1.07%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2.25%

[1]

'

2.50%

[1]

'

'

'

'

'

'

'

'

'

'

'

2.50%

'

'

'

'

2.50%

[1]

'

'

'

2.25%

[1]

'

'

'

'

'

2.50%

'

'

2.50%

'

2.50%

'

2.50%

[1]

'

2.50%

[1]

'

'

'

'

'

'

2.63%

'

2.00%

2.00%

2.63%

'

'

'

'

'

'

'

'

'

'

'

Interest rate, range, minimum

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.61%

[1]

'

'

'

2.25%

[1]

2.40%

[1]

'

1.12%

[1]

'

'

'

'

'

'

'

'

'

'

7.12%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate, range, maximum

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3.58%

[1]

'

'

'

2.75%

[1]

3.47%

[1]

'

4.26%

[1]

'

'

'

'

'

'

'

'

'

'

7.25%

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate, Chalk Point capital lease

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8.19%

[1]

'

'

'

'

'

'

'

'

Additional borrowings

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

450

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

164

'

62

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt redeemed and re-issued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

407

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Repurchase/redemption price, percentage of face amount (as a percent)

'

'

'

'

'

'

'

'

'

'

'

114.18%

'

'

111.70%

'

'

113.08%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

99.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

106.78%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss on debt extinguishment

1

41

50

41

'

'

'

'

'

28

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3

'

'

'

7

'

'

'

'

'

'

'

'

'

'

'

'

'

11

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Generation Capacity (in MW)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

20

20

'

'

Debt issuance costs

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

'

23

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt instrument, discount on issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum borrowing capacity, amendment, amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

211

211

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

63

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum borrowing capacity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,500

2,500

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

166

'

'

'

68

'

'

'

'

'

'

'

'

'

'

'

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

60

Repurchased/redeemed debt, face value

'

'

'

'

'

'

'

'

'

'

200

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

575

575

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cash paid for senior notes repurchases

'

'

'

'

'

'

'

'

'

'

'

80

'

'

104

'

'

42

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Letters of credit issued and outstanding at period end, amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

37

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

9

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

26

'

Issued letters of credit returned, amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

82

'

'

'

'

Debt instrument, face amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

36

'

'

'

45

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate, escalation percent of basis spread on variable rate (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.25%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.25%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, escalation period of basis spread on variable rate (in years)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'4 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Letters of credit, availability fee, percentage of applicable margin (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of interest rate swaps

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate swaps, minimum percent of outstanding notional amount required to have a fixed interest rate (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

75.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate swaps, fixed interest payment rate equivalent (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.13%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Notional Amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

15

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt instrument, period payment is due after receipt of cash (in days)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'10 days

'

'

'

'

'

'

'

'

'

'

'

'

'10 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of credit facility, maximum borrowing capacity available for issuance of letters of credit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$9

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

As of September 30, 2013, L+ equals 3 month LIBOR plus x%, with the exception of NRG Solar Alpine LLC cash grant loan and NRG Solar Kansas South LLC cash grant bridge loan which are 1 month LIBOR plus x% and NRG Solar Kansas South LLC term loan which is 6 month LIBOR plus x%.

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Investments Accounted for by the Equity Method	'	'
Equity investments in affiliates	$626	$676
GenConn Energy LLC	'	'
Investments Accounted for by the Equity Method	'	'
Economic interest in equity method investments (as a percent)	50.00%	'
Power generation units	2	'
Generation Capacity (in MW)	190	'
Equity investments in affiliates	118	'
Sherbino I Wind Farm LLC	'	'
Investments Accounted for by the Equity Method	'	'
Economic interest in equity method investments (as a percent)	50.00%	'
Equity investments in affiliates	88	'
Texas Coastal Ventures LLC	'	'
Investments Accounted for by the Equity Method	'	'
Economic interest in equity method investments (as a percent)	50.00%	'
Equity investments in affiliates	$63	'

Changes_in_Capital_Structure_D

Changes in Capital Structure (Details)	3 Months Ended			9 Months Ended		0 Months Ended
	Mar. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Sep. 30, 2013	Oct. 18, 2013
				Common Stock	Treasury Stock	Edison Mission Energy
						Subsequent Event
						Common Stock
Common stock authorized (in shares)	'	'	'	'	'	'
Common stock, shares authorized	'	500,000,000	500,000,000	'	'	'
Changes in common stock issued and outstanding (in shares)	'	'	'	'	'	'
Shares issued, balance at the beginning of the year	399,112,616	400,675,096	'	'	'	'
Shares outstanding, balance at the beginning of the year	322,606,898	323,327,568	'	'	'	'
Shares issued from LTIP	'	'	'	1,562,480	'	'
Shares issued under ESPP	'	'	'	130,482	130,482	'
Shares issued, balance at the end of the year	'	400,675,096	'	'	'	'
Shares outstanding, balance at the end of the year	'	323,327,568	'	'	'	'
Changes in treasury stock (in shares)	'	'	'	'	'	'
Treasury shares, balance at the beginning of the year	-76,505,718	-77,347,528	'	'	'	'
Shares issued under ESPP	'	'	'	130,482	130,482	'
Shares repurchased under Capital Allocation Program	972,292	'	'	-972,292	972,292	'
Treasury shares, balance at the beginning of the year	'	-77,347,528	'	'	'	'
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	'	'	'	'	'	12,671,977

Changes_in_Capital_Structure_D1

Changes in Capital Structure (Details 2) (USD $)	3 Months Ended				9 Months Ended		3 Months Ended		12 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Feb. 27, 2013
							Subsequent Event	Scenario, Forecast	Scenario, Forecast	Scenario, Plan [Member]	Scenario, Plan [Member]
Employee Stock Purchase Plan and 2013 Capital Allocation Plan	'	'	'	'	'	'	'	'	'	'	'
NRG's annual common stock dividend, propsed increase for 2013 (as a percent)	'	'	'	'	'	'	'	'	'	'	33.00%
NRG's annual common stock dividend, proposed amount for 2013	'	'	'	'	'	'	'	'	'	$0.48	'
Dividend paid	$0.12	$0.12	$0.09	$0.09	$0.33	$0.09	'	'	'	'	'
Dividend declared	'	'	'	'	'	'	$0.12	'	'	'	'
Shares repurchased under Capital Allocation Program, dollar amount authorized	'	'	'	'	'	'	'	'	$200	'	'
Shares repurchased under Capital Allocation Program	'	'	972,292	'	'	'	'	'	'	'	'
Shares repurchased under Capital Allocation Program, value	'	'	25	'	'	'	'	'	'	'	'
Shares repurchased under Capital Allocation Program, weighted average value per share	'	'	$25.88	'	'	'	'	'	'	'	'
Shares repurchased under Capital Allocation Program, remaining dollar amount authorized	'	'	'	'	'	'	'	$175	'	'	'

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Numerator:	'	'	'	'	'
Net income/(loss) attributable to NRG Energy, Inc.	$124	($1)	($74)	$43	'
Dividends for preferred shares	2	2	7	7	'
Income/(loss) Available for Common Stockholders	$122	($3)	($81)	$36	'
Denominator:	'	'	'	'	'
Weighted average number of common shares outstanding	323	228	323	228	'
Basic earnings per share:	'	'	'	'	'
Earnings/(loss) per weighted average common share — basic	$0.38	($0.01)	($0.25)	$0.16	'
Denominator (diluted earnings per share):	'	'	'	'	'
Incremental shares attributable to the issuance of equity compensation (treasury stock method)	4	0	0	2	'
Total dilutive shares	327	228	323	230	'
Diluted earnings per share:	'	'	'	'	'
Diluted earnings per share attributable to NRG common stockholders	$0.37	($0.01)	($0.25)	$0.16	'
Antidilutive Securities Excluded from Computation of Earnings Per Share	'	'	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share, amount	18	27	26	22	'
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	3.63%	3.63%	3.63%	3.63%	3.63%
Equity compensation plans	'	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share	'	'	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share, amount	2	11	10	6	'
Embedded derivative of 3.625% redeemable perpetual preferred stock	'	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share	'	'	'	'	'
Antidilutive securities excluded from computation of diluted earnings per share, amount	16	16	16	16	'

Segment_Reporting_Details

Segment Reporting (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Segment Reporting Information	'		'		'		'		'
Operating revenues	$3,490		$2,331		$8,500		$6,359		'
Depreciation and amortization	318		239		921		703		'
Equity in earnings/(losses) of unconsolidated affiliates	-5		4		6		26		'
(Loss)/income before income taxes	306		-105		-94		-185		'
Net income/(loss) attributable to NRG Energy, Inc.	124		-1		-74		43		'
Total assets	34,863		'		34,863		'		35,104
Includes loss on debt extinguishment of	1		41		50		41		'
Retail	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	1,994	[1]	1,856	[2]	4,760	[3]	4,492	[4]	'
Depreciation and amortization	37	[1]	41	[2]	105	[3]	126	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	0	[1]	0	[2]	0	[3]	0	[4]	'
(Loss)/income before income taxes	-60	[1]	-300	[2]	231	[3]	504	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	-60	[1]	-300	[2]	231	[3]	504	[4]	'
Total assets	4,296	[1]	'		4,296	[1]	'		'
Includes intersegment sales and derivative gains and losses of	2		3		4		3		'
Conventional Power Generation | Texas	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	881	[1]	877	[2]	1,712	[3]	1,462	[4]	'
Depreciation and amortization	116	[1]	115	[2]	340	[3]	343	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	0	[1]	0	[2]	0	[3]	0	[4]	'
(Loss)/income before income taxes	265	[1]	299	[2]	14	[3]	-202	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	265	[1]	299	[2]	14	[3]	-202	[4]	'
Total assets	11,914	[1]	'		11,914	[1]	'		'
Includes intersegment sales and derivative gains and losses of	910		1,126		1,732		1,287		'
Conventional Power Generation | East	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	1,011	[1]	274	[2]	2,432	[3]	598	[4]	'
Depreciation and amortization	79	[1]	32	[2]	236	[3]	96	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	0	[1]	0	[2]	0	[3]	0	[4]	'
(Loss)/income before income taxes	245	[1]	30	[2]	238	[3]	-31	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	245	[1]	30	[2]	238	[3]	-31	[4]	'
Total assets	8,329	[1]	'		8,329	[1]	'		'
Includes intersegment sales and derivative gains and losses of	55		6		99		51		'
Conventional Power Generation | South Central	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	244	[1]	270	[2]	656	[3]	653	[4]	'
Depreciation and amortization	24	[1]	23	[2]	73	[3]	69	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	1	[1]	0	[2]	3	[3]	0	[4]	'
(Loss)/income before income taxes	17	[1]	19	[2]	17	[3]	0	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	17	[1]	19	[2]	17	[3]	0	[4]	'
Total assets	2,290	[1]	'		2,290	[1]	'		'
Includes intersegment sales and derivative gains and losses of	0		0		16		0		'
Conventional Power Generation | West	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	134		87	[2]	347	[3]	185	[4]	'
Depreciation and amortization	13		3	[2]	37	[3]	8	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	-10		4	[2]	-8	[3]	6	[4]	'
(Loss)/income before income taxes	30		35	[2]	62	[3]	42	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	30		35	[2]	62	[3]	42	[4]	'
Total assets	1,553		'		1,553		'		'
Includes intersegment sales and derivative gains and losses of	0		0		3		0		'
Conventional Power Generation | Other	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	38	[1]	28	[2]	110	[3]	152	[4]	'
Depreciation and amortization	1	[1]	1	[2]	3	[3]	1	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	0	[1]	3	[2]	2	[3]	8	[4]	'
(Loss)/income before income taxes	1	[1]	5	[2]	3	[3]	22	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	1	[1]	5	[2]	2	[3]	18	[4]	'
Total assets	461	[1]	'		461	[1]	'		'
Includes intersegment sales and derivative gains and losses of	15		12		48		55		'
Alternative Energy	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	83	[1]	49	[2]	177	[3]	91	[4]	'
Depreciation and amortization	27	[1]	15	[2]	78	[3]	34	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	-3	[1]	-9	[2]	-7	[3]	-3	[4]	'
(Loss)/income before income taxes	1	[1]	-8	[2]	-48	[3]	-27	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	-21	[1]	-16	[2]	-75	[3]	-45	[4]	'
Total assets	6,162	[1]	'		6,162	[1]	'		'
Includes intersegment sales and derivative gains and losses of	8		10		19		18		'
NRG Yield	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	95	[1]	47	[2]	227	[3]	133	[4]	'
Depreciation and amortization	16	[1]	6	[2]	35	[3]	18	[4]	'
Equity in earnings/(losses) of unconsolidated affiliates	12	[1]	6	[2]	18	[3]	15	[4]	'
(Loss)/income before income taxes	45	[1]	12	[2]	90	[3]	18	[4]	'
Net income/(loss) attributable to NRG Energy, Inc.	31	[1]	4	[2]	76	[3]	8	[4]	'
Total assets	2,331	[1]	'		2,331	[1]	'		'
Includes intersegment sales and derivative gains and losses of	0		0		0		0		'
Corporate	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	0	[1],[5]	4	[2],[6]	9	[3],[7]	11	[4],[6]	'
Depreciation and amortization	5	[1],[5]	3	[2],[6]	14	[3],[7]	8	[4],[6]	'
Equity in earnings/(losses) of unconsolidated affiliates	0	[1],[5]	0	[2],[6]	0	[3],[7]	0	[4],[6]	'
(Loss)/income before income taxes	-217	[1],[5]	-197	[2],[6]	-695	[3],[7]	-511	[4],[6]	'
Net income/(loss) attributable to NRG Energy, Inc.	-375	[1],[5]	-77	[2],[6]	-642	[3],[7]	-251	[4],[6]	'
Total assets	4,863	[1],[5]	'		4,863	[1],[5]	'		'
Includes loss on debt extinguishment of	1		41		50		41		'
Includes intersegment sales and derivative gains and losses of	0		4		9		4		'
Elimination	'		'		'		'		'
Segment Reporting Information	'		'		'		'		'
Operating revenues	-990		-1,161		-1,930		-1,418		'
Depreciation and amortization	0		0		0		0		'
Equity in earnings/(losses) of unconsolidated affiliates	-5		0		-2		0		'
(Loss)/income before income taxes	-21		0		-6		0		'
Net income/(loss) attributable to NRG Energy, Inc.	-9		0		3		0		'
Total assets	($7,336)		'		($7,336)		'		'
[1]	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:$2 $910 $55 $— $— $15 $8 $— $—
[2]	(c) Operating revenues include inter-segment sales and net derivative gains and losses of:$3 $1,126 $6 $— $— $12 $10 $— $4
[3]	(e) Operating revenues include inter-segment sales and net derivative gains and losses of:$4 $1,732 $99 $16 $3 $48 $19 — $9
[4]	(g) Operating revenues include inter-segment sales and net derivative gains and losses of:$3 $1,287 $51 $— $— $55 $18 $— $4
[5]	Includes loss on debt extinguishment of $1 million.
[6]	Includes loss on debt extinguishment of $41 million.
[7]	Includes loss on debt extinguishment of $50 million.

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Effective Tax Rate	'	'	'	'
Income/(loss) before income taxes	$306	($105)	($94)	($185)
Income tax expense/(benefit)	163	-113	-47	-246
Effective tax rate (as a percent)	53.30%	107.60%	50.00%	133.00%
Statutory tax rate (as a percent)	35.00%	35.00%	35.00%	35.00%
Uncertain Tax Benefits	'	'	'	'
Non-current tax liability for uncertain tax benefits	74	'	74	'
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	'	'	1	'
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$17	'	$17	'

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)

1 Months Ended

3 Months Ended

12 Months Ended

61 Months Ended

0 Months Ended

1 Months Ended

4 Months Ended

9 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

13 Months Ended

1 Months Ended

9 Months Ended

0 Months Ended

Mar. 31, 2013

Sep. 30, 2013

Dec. 31, 2008

Mar. 31, 2018

Sep. 30, 2013

Sep. 30, 2013

Mar. 06, 2013

Jul. 31, 2013

Apr. 30, 2013

Apr. 30, 2012

Jun. 30, 2013

Sep. 30, 2012

Jun. 30, 2013

Mar. 31, 2013

Jan. 31, 2013

Feb. 28, 2008

Sep. 30, 2013

Dec. 31, 2011

Sep. 30, 2013

Dec. 31, 2012

Jun. 30, 2013

Jun. 30, 2013

Jul. 31, 2011

Sep. 30, 2013

Apr. 30, 2011

Sep. 30, 2010

Feb. 28, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Nov. 12, 2013

Weeks

Nuclear Event

Non-nuclear Event

Louisiana Generating, LLC

New Source Review

New Source Review

Cheswick Class Action

Ormond Beach Alleged Federal Clean Water Act Violations

Agreement To Acquire All Outstanding Shares of GenOn

Notice of Intent to File Citizens Suit

Notice of Intent to File Citizens Suit

Notice of Intent to File Citizens Suit

Global Warming

Maryland Fly Ash

GenOn Mid-Atlantic

GenOn Mid-Atlantic

GenOn Mid-Atlantic

GenOn Energy

GenOn Energy

GenOn Energy

GenOn Energy

GenOn Mid-Atlantic and GenOn MD Ash Management

GenOn Mid-Atlantic and GenOn MD Ash Management

Energy Plus

Energy Plus

New York

New Jersey

Pennsylvania

Subsequent Event

Months

nov

mi

Lawsuits

permit

Environmental Issue

fly_ash_facility

Maryland Fly Ash

Maryland Fly Ash

Maryland Fly Ash

Texas Franchise Audit

Natural Gas Litigation

Natural Gas Litigation

Natural Gas Litigation

Brandywine Litigation, Coal Combusion Waste

Brandywine Litigation, Coal Combusion Waste

Class Action Related to Sales, Marketing and Business Practices

Class Action Related to Sales, Marketing and Business Practices

Energy Plus

Energy Plus

Energy Plus

Big Cajun II Alleged Opacity Violations

year

facility

companies

Environmental Issue

Environmental Issue

Environmental Issue

legal_cases

Lawsuits

Lawsuits

environmental_advocy_group

Lawsuits

Lawsuits

Class Action Related to Sales, Marketing and Business Practices

Class Action Related to Sales, Marketing and Business Practices

Class Action Related to Sales, Marketing and Business Practices

fly_ash_facility

Lawsuits

Lawsuits

Lawsuits

Loss Contingencies

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Annual Coverage Limit

'

$13,600,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Requirement Per Site

'

375,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Financial Protection Pool Value

'

13,200,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Financial Protection Pool, Maximum Assessment

'

127,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Financial Protection Pool, Maximum Assessment, Adminstrative Fee, As a Percent

'

5.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mutual Property Insurance Total Property Coverage

'

'

'

'

2,750,000,000

1,500,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mutual Property Insurance Additional Blanket Policy Property Coverage

'

1,000,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Mutual Property Insurance Individual Maximum Property Coverage Limit

'

1,750,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Additional Mutual Lost Revenue Insurance Weekly Maximum

'

1,980,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Accidental Outage Maximum Recovery For Lost Revenues

'

'

'

'

215,600,000

144,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Financial Protection Pool Maximum Annual Assessment

'

19,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Forty-Four Percent Maximum Assessment

'

44.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Financial Protection Pool Nuclear Operator Maximum Annual Assessment

'

8,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Nuclear Insurance Financial Protection Pool Nuclear Operator Total Assessment

'

112,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Twenty-Three Weeks Waiting Period

'

8

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Industry Mutual Insurance Company Multiplier

'

10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Twenty-Four Months

'

24

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number Of Years Board Of Directors Of Industry Mutual Insurance Company Can Adjust Policy After Policy Expires

'

6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Civil Penalties

3,500,000

'

'

'

'

'

3,500,000

'

'

'

'

'

100,000

'

'

'

'

1,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Loss in Period

'

'

'

10,500,000

'

'

10,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Range of Possible Loss, Maximum

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

400,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

number of companies also included in lawsuit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

23

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Number of NOVs Issued

'

'

'

'

'

'

'

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Facilities

'

'

'

'

'

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Litigation Settlement, Amount

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

47,000

Litigation Settlement, Review Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'90 days

Distance From Facility of People who Own Property

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum Civil Penalties which May Be Assumed

'

'

200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency Obligation, Legal Fees

'

'

'

'

'

'

'

'

'

'

79,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency Obligation, Supplemental Environmental Projects

'

'

'

'

'

'

'

'

'

'

65,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency Obligation, Monitoring Costs

'

'

'

'

'

'

'

'

'

'

15,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Fly Ash Facilities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Requested Period of Time for Open Disposal Cells to be Closed and Capped

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'1 year

'

'

'

'

'

'

'

Number of Environmental Advocacy Groups, Intervening Parties to Litigation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

'

'

'

'

'

Civil Penalties, Accrued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

600,000

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency Accrual, at Carrying Value

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

47,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Number of Plaintiffs

'

'

'

'

'

'

'

'

'

'

'

8

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6

2

2

2

'

Loss Contingency, Claims Settled and Dismissed, Number

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1

4

'

'

'

6

'

'

'

'

'

Loss Contingency, Pending Claims, Number

'

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

5

'

'

'

'

'

'

'

'

Number of Permits that Regulate Polution Discharge Elimination

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Loss Contingency, Number of Days to Comply with Discharge Violation

'

'

'

'

'

'

'

'

'

'

'

'

'

'60 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Income Tax Examination, Penalties and Interest Accrued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

72,000,000

'

'

'

'

'

'

'

'

'

'

'

Income Tax Examination, Interest Accrued

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

29,000,000

'

'

'

'

'

'

'

'

'

'

'

Tax Adjustments, Settlements, and Unusual Provisions

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$11,000,000

'

'

'

'

'

'

'

'

'

'

'

Regulatory_Matters_Details

Regulatory Matters (Details) (USD $)	1 Months Ended
In Millions, unless otherwise specified	31-May-10	Jul. 05, 2012	Dec. 31, 2011
	orders	owners
Regulatory Matters Disclosure [Abstract]	'	'	'
Number of Significant Orders Issued by Authority	2	'	'
SECA charges owed by BP Energy	'	'	$22
Regulatory Charges Settled by Third Party	'	24	'
Number of PJM Transmission Owners Who Filed Motion	'	3	'
Regulatory Charges Settled by Third Party, Additional	'	$1	'

Environmental_Matters_Details

Environmental Matters (Details) (USD $)	1 Months Ended	12 Months Ended	61 Months Ended
	Mar. 31, 2013	Dec. 31, 2008	Mar. 31, 2018	Sep. 30, 2013
Environmental Matters Disclosure [Abstract]	'	'	'	'
Estimated environmental capital expenditures from 2013 through 2017	'	'	'	$530,000,000
Estimated environmental capital expenditures from 2013 through 2017, attributable to GenOn	'	'	'	223,000,000
Minimum Civil Penalties which May Be Assumed	'	200,000	'	'
Civil Penalties	3,500,000	'	'	'
Loss Contingency, Loss in Period	'	'	$10,500,000	'

Condensed_Consolidating_Financ2

Condensed Consolidating Financial Information (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Debt Instrument	'	'
Long-term debt	$16,699	$15,866
Recourse Debt	'	'
Debt Instrument	'	'
Long-term debt	8,091	7,818
Senior Notes [Member] | Recourse Debt	'	'
Debt Instrument	'	'
Long-term debt	$5,700	'

Condensed_Consolidating_Financ3

Condensed Consolidating Financial Information (Details 2) (USD $)	3 Months Ended					9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2013		Sep. 30, 2012
Operating Revenues	'		'		'	'		'
Total operating revenues	$3,490		$2,331		'	$8,500		$6,359
Operating Costs and Expenses	'		'		'	'		'
Cost of operations	2,355		1,740		'	6,179		4,660
Depreciation and amortization	318		239		'	921		703
Selling, general and administrative	229		224		'	671		613
Acquisition-related transaction and integration costs	26		18		'	95		18
Development activity expenses	27		24		'	63		52
Costs and Expenses	2,955		2,245		'	7,929		6,046
Operating Income (Loss)	535		86		'	571		313
Other Income/(Expense)	'		'		'	'		'
Equity in earnings/(losses) of consolidated subsidiaries	0		0		'	0		0
Equity in (losses)/earnings of unconsolidated affiliates	-5		4		'	6		26
Other income, net	5		9		'	9		12
Loss on debt extinguishment	-1		-41		'	-50		-41
Interest expense	-228		-163		'	-630		-495
Total other expense	-229		-191		'	-665		-498
(Loss)/income before income taxes	306		-105		'	-94		-185
Income tax expense/(benefit)	163		-113		'	-47		-246
Net Income/(Loss)	143		8		'	-47		61
Less: Net income attributable to noncontrolling interest	19		9		'	27		18
Net income/(loss) attributable to NRG Energy, Inc.	124		-1		'	-74		43
Other Comprehensive Income/(Loss), net of tax	'		'		'	'		'
Unrealized (loss)/gain on derivatives, net	-16		-43		'	8		-132
Foreign currency translation adjustments, net	5		1		'	-14		-1
Reclassification adjustment for translation gain realized upon sale of Schkopau, net of income tax expense of $0, $6, $0 and $6	0		-11		'	0		-11
Available-for-sale securities, net	0		2		2	2		2
Defined benefit plan, net	0		0		'	25		0
Other comprehensive (loss)/income	-11		-51		'	21		-142
Comprehensive income/(loss)	132		-43		'	-26		-81
Comprehensive income attributable to noncontrolling interest	18		9		'	26		18
Comprehensive income/(loss) attributable to NRG Energy, Inc.	114		-52		'	-52		-99
Dividends for preferred shares	-2		-2		'	-7		-7
Comprehensive Income/(Loss) Available for Common Stockholders	112		-54		'	-59		-106
Guarantor Subsidiaries	'		'		'	'		'
Operating Revenues	'		'		'	'		'
Total operating revenues	2,464		2,237		'	6,225		6,058
Operating Costs and Expenses	'		'		'	'		'
Cost of operations	1,792		1,715		'	4,697		4,512
Depreciation and amortization	213		217		'	624		647
Selling, general and administrative	116		154		'	341		387
Acquisition-related transaction and integration costs	0		0		'	0		0
Development activity expenses	0		0		'	0		0
Costs and Expenses	2,121		2,086		'	5,662		5,546
Operating Income (Loss)	343		151		'	563		512
Other Income/(Expense)	'		'		'	'		'
Equity in earnings/(losses) of consolidated subsidiaries	-25		-10		'	-4		6
Equity in (losses)/earnings of unconsolidated affiliates	-10		4		'	-8		6
Other income, net	5		0		'	7		0
Loss on debt extinguishment	0		0		'	0		0
Interest expense	-3		5		'	-13		21
Total other expense	-33		-11		'	-18		-9
(Loss)/income before income taxes	310		140		'	545		503
Income tax expense/(benefit)	126		67		'	212		193
Net Income/(Loss)	184		73		'	333		310
Less: Net income attributable to noncontrolling interest	0		0		'	0		0
Net income/(loss) attributable to NRG Energy, Inc.	184		73		'	333		310
Other Comprehensive Income/(Loss), net of tax	'		'		'	'		'
Unrealized (loss)/gain on derivatives, net	-13		-43		'	-54		-122
Foreign currency translation adjustments, net	0		0		'	0		0
Reclassification adjustment for translation gain realized upon sale of Schkopau, net of income tax expense of $0, $6, $0 and $6	'		'		'	'		0
Available-for-sale securities, net	'		0		'	0		0
Defined benefit plan, net	'		'		'	0		'
Other comprehensive (loss)/income	-13		-43		'	-54		-122
Comprehensive income/(loss)	171		30		'	279		188
Comprehensive income attributable to noncontrolling interest	0		0		'	0		0
Comprehensive income/(loss) attributable to NRG Energy, Inc.	171		30		'	279		188
Dividends for preferred shares	0		0		'	0		0
Comprehensive Income/(Loss) Available for Common Stockholders	171		30		'	279		188
Non-Guarantor Subsidiaries	'		'		'	'		'
Operating Revenues	'		'		'	'		'
Total operating revenues	1,019		120		'	2,394		353
Operating Costs and Expenses	'		'		'	'		'
Cost of operations	566		47		'	1,593		186
Depreciation and amortization	102		20		'	288		48
Selling, general and administrative	70		0		'	173		6
Acquisition-related transaction and integration costs	13		0		'	54		0
Development activity expenses	14		14		'	24		22
Costs and Expenses	765		81		'	2,132		262
Operating Income (Loss)	254		39		'	262		91
Other Income/(Expense)	'		'		'	'		'
Equity in earnings/(losses) of consolidated subsidiaries	-5		1		'	-9		-11
Equity in (losses)/earnings of unconsolidated affiliates	10		0		'	16		20
Other income, net	3		2		'	5		4
Loss on debt extinguishment	-1		0		'	-12		0
Interest expense	-88		21		'	-229		60
Total other expense	-81		-18		'	-229		-47
(Loss)/income before income taxes	173		21		'	33		44
Income tax expense/(benefit)	59		-27		'	-10		-122
Net Income/(Loss)	114		48		'	43		166
Less: Net income attributable to noncontrolling interest	32		9		'	40		18
Net income/(loss) attributable to NRG Energy, Inc.	82		39		'	3		148
Other Comprehensive Income/(Loss), net of tax	'		'		'	'		'
Unrealized (loss)/gain on derivatives, net	-8		-14		'	41		-33
Foreign currency translation adjustments, net	4		0		'	-11		-2
Reclassification adjustment for translation gain realized upon sale of Schkopau, net of income tax expense of $0, $6, $0 and $6	'		'		'	'		-11
Available-for-sale securities, net	'		0		'	0		0
Defined benefit plan, net	'		'		'	-25		'
Other comprehensive (loss)/income	-4		-25		'	55		-46
Comprehensive income/(loss)	110		23		'	98		120
Comprehensive income attributable to noncontrolling interest	29		9		'	39		18
Comprehensive income/(loss) attributable to NRG Energy, Inc.	81		14		'	59		102
Dividends for preferred shares	0		0		'	0		0
Comprehensive Income/(Loss) Available for Common Stockholders	81		14		'	59		102
NRG Energy, Inc.	'		'		'	'		'
Operating Revenues	'		'		'	'		'
Total operating revenues	0		0		'	0		0
Operating Costs and Expenses	'		'		'	'		'
Cost of operations	-6		1		'	1		7
Depreciation and amortization	3		2		'	9		8
Selling, general and administrative	39		73		'	164		227
Acquisition-related transaction and integration costs	13		18		'	41		18
Development activity expenses	13		10		'	39		30
Costs and Expenses	62		104		'	254		290
Operating Income (Loss)	-62		-104		'	-254		-290
Other Income/(Expense)	'		'		'	'		'
Equity in earnings/(losses) of consolidated subsidiaries	309		121		'	363		463
Equity in (losses)/earnings of unconsolidated affiliates	0		0		'	0		0
Other income, net	1		7		'	3		8
Loss on debt extinguishment	0		-41		'	-38		-41
Interest expense	-137		137		'	-388		414
Total other expense	173		-50		'	-60		16
(Loss)/income before income taxes	111		-154		'	-314		-274
Income tax expense/(benefit)	-22		-153		'	-249		-317
Net Income/(Loss)	133		-1		'	-65		43
Less: Net income attributable to noncontrolling interest	9		0		'	9		0
Net income/(loss) attributable to NRG Energy, Inc.	124		-1		'	-74		43
Other Comprehensive Income/(Loss), net of tax	'		'		'	'		'
Unrealized (loss)/gain on derivatives, net	17		-54		'	9		-145
Foreign currency translation adjustments, net	1		1		'	-3		1
Reclassification adjustment for translation gain realized upon sale of Schkopau, net of income tax expense of $0, $6, $0 and $6	'		'		'	'		0
Available-for-sale securities, net	'		2		'	2		2
Defined benefit plan, net	'		'		'	0		'
Other comprehensive (loss)/income	18		-51		'	8		-142
Comprehensive income/(loss)	151		-52		'	-57		-99
Comprehensive income attributable to noncontrolling interest	9		0		'	9		0
Comprehensive income/(loss) attributable to NRG Energy, Inc.	142		-52		'	-66		-99
Dividends for preferred shares	-2		-2		'	-7		-7
Comprehensive Income/(Loss) Available for Common Stockholders	140		-54		'	-73		-106
Eliminations	'		'		'	'		'
Operating Revenues	'		'		'	'		'
Total operating revenues	7	[1]	-26	[1]	'	-119	[1]	-52	[1]
Operating Costs and Expenses	'		'		'	'		'
Cost of operations	3	[1]	-23	[1]	'	-112	[1]	-45	[1]
Depreciation and amortization	0	[1]	0	[1]	'	0	[1]	0	[1]
Selling, general and administrative	4	[1]	-3	[1]	'	-7	[1]	-7	[1]
Acquisition-related transaction and integration costs	0	[1]	0	[1]	'	0	[1]	0	[1]
Development activity expenses	0	[1]	0		'	0	[1]	0	[1]
Costs and Expenses	7	[1]	-26	[1]	'	-119	[1]	-52	[1]
Operating Income (Loss)	0	[1]	0	[1]	'	0	[1]	0	[1]
Other Income/(Expense)	'		'		'	'		'
Equity in earnings/(losses) of consolidated subsidiaries	-279	[1]	-112	[1]	'	-350	[1]	-458	[1]
Equity in (losses)/earnings of unconsolidated affiliates	-5	[1]	0	[1]	'	-2	[1]	0	[1]
Other income, net	-4	[1]	0	[1]	'	-6	[1]	0	[1]
Loss on debt extinguishment	0	[1]	0	[1]	'	0	[1]	0	[1]
Interest expense	0	[1]	0		'	0	[1]	0	[1]
Total other expense	-288	[1]	-112	[1]	'	-358	[1]	-458	[1]
(Loss)/income before income taxes	-288	[1]	-112	[1]	'	-358	[1]	-458	[1]
Income tax expense/(benefit)	0	[1]	0		'	0	[1]	0	[1]
Net Income/(Loss)	-288	[1]	-112	[1]	'	-358	[1]	-458	[1]
Less: Net income attributable to noncontrolling interest	-22	[1]	0		'	-22	[1]	0	[1]
Net income/(loss) attributable to NRG Energy, Inc.	-266	[1]	-112	[1]	'	-336	[1]	-458	[1]
Other Comprehensive Income/(Loss), net of tax	'		'		'	'		'
Unrealized (loss)/gain on derivatives, net	-12	[1]	68	[1]	'	12	[1]	168	[1]
Foreign currency translation adjustments, net	0	[1]	0	[1]	'	0	[1]	0	[1]
Reclassification adjustment for translation gain realized upon sale of Schkopau, net of income tax expense of $0, $6, $0 and $6	'		'		'	'		0	[1]
Available-for-sale securities, net	'		0	[1]	'	0	[1]	0	[1]
Defined benefit plan, net	'		'		'	0	[1]	'
Other comprehensive (loss)/income	-12	[1]	68	[1]	'	12	[1]	168	[1]
Comprehensive income/(loss)	-300	[1]	-44	[1]	'	-346	[1]	-290	[1]
Comprehensive income attributable to noncontrolling interest	-20	[1]	0	[1]	'	-22	[1]	0	[1]
Comprehensive income/(loss) attributable to NRG Energy, Inc.	-280	[1]	-44	[1]	'	-324	[1]	-290	[1]
Dividends for preferred shares	0	[1]	0	[1]	'	0	[1]	0	[1]
Comprehensive Income/(Loss) Available for Common Stockholders	($280)	[1]	($44)	[1]	'	($324)	[1]	($290)	[1]
[1]	All significant intercompany transactions have been eliminated in consolidation.

Condensed_Consolidating_Financ4

Condensed Consolidating Financial Information (Details 3) (USD $)	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2012		Dec. 31, 2011
In Millions, unless otherwise specified
Current Assets	'		'		'		'
Cash and cash equivalents	$2,129		$2,087		$1,610		$1,105
Funds deposited by counterparties	122		271		'		'
Restricted cash	307		217		'		'
Accounts receivable-trade, net	1,366		1,061		'		'
Inventory	861		911		'		'
Derivative instruments	1,389		2,644		'		'
Deferred income taxes	0		56		'		'
Cash collateral paid in support of energy risk management activities	288		229		'		'
Renewable energy grant receivable	345		58		'		'
Prepayments and other current assets	442		401		'		'
Total current assets	7,249		7,935		'		'
Net property, plant and equipment	20,600		20,241		'		'
Other Assets	'		'		'		'
Investment in subsidiaries	0		0		'		'
Equity investments in affiliates	626		676		'		'
Capital leases and notes receivable, less current portion	76		79		'		'
Goodwill	1,953		1,956		'		'
Intangible assets, net	1,141		1,200		'		'
Nuclear decommissioning trust fund	524		473		'		'
Deferred income taxes	1,499		1,282		'		'
Derivative instruments	506		662		'		'
Other non-current assets	689		600		'		'
Total other assets	7,014		6,928		'		'
Total assets	34,863		35,104		'		'
Current Liabilities	'		'		'		'
Current portion of long-term debt and capital leases	911		147		'		'
Accounts payable	1,140		1,171		'		'
Accounts payable — affiliate	0		0		'		'
Derivative instruments	1,064		1,981		'		'
Deferred income taxes	112		0		'		'
Cash collateral received in support of energy risk management activities	122		271		'		'
Accrued expenses and other current liabilities	1,033		1,085		'		'
Total current liabilities	4,382		4,655		'		'
Other Liabilities	'		'		'		'
Long-term debt and capital leases	15,802		15,736		'		'
Nuclear decommissioning reserve	290		354		'		'
Nuclear decommissioning trust liability	303		273		'		'
Deferred income taxes	50		55		'		'
Derivative instruments	372		500		'		'
Out-of-market contracts	1,157		1,231		'		'
Other non-current liabilities	1,377		1,553		'		'
Total non-current liabilities	19,351		19,702		'		'
Total Liabilities	23,733		24,357		'		'
3.625% convertible perpetual preferred stock	249		249		'		'
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	3.63%		3.63%		3.63%		'
Total Stockholders' Equity	10,881		10,498		'		'
Total Liabilities and Stockholders' Equity	34,863		35,104		'		'
Guarantor Subsidiaries	'		'		'		'
Current Assets	'		'		'		'
Cash and cash equivalents	23		78		11		44
Funds deposited by counterparties	0		131		'		'
Restricted cash	18		11		'		'
Accounts receivable-trade, net	1,132		807		'		'
Inventory	406		472		'		'
Derivative instruments	914		2,058		'		'
Deferred income taxes	'		-153		'		'
Cash collateral paid in support of energy risk management activities	253		81		'		'
Renewable energy grant receivable	0		0		'		'
Prepayments and other current assets	4,103		2,966		'		'
Total current assets	6,849		6,451		'		'
Net property, plant and equipment	9,651		9,905		'		'
Other Assets	'		'		'		'
Investment in subsidiaries	108		244		'		'
Equity investments in affiliates	18		33		'		'
Capital leases and notes receivable, less current portion	0		3		'		'
Goodwill	1,941		1,944		'		'
Intangible assets, net	988		1,042		'		'
Nuclear decommissioning trust fund	524		473		'		'
Deferred income taxes	0		-915		'		'
Derivative instruments	202		149		'		'
Other non-current assets	80		85		'		'
Total other assets	3,861		3,058		'		'
Total assets	20,361		19,414		'		'
Current Liabilities	'		'		'		'
Current portion of long-term debt and capital leases	1		1		'		'
Accounts payable	678		541		'		'
Accounts payable — affiliate	6		-55		'		'
Derivative instruments	887		1,726		'		'
Deferred income taxes	369		'		'		'
Cash collateral received in support of energy risk management activities	0		131		'		'
Accrued expenses and other current liabilities	283		354		'		'
Total current liabilities	2,224		2,698		'		'
Other Liabilities	'		'		'		'
Long-term debt and capital leases	316		310		'		'
Nuclear decommissioning reserve	290		354		'		'
Nuclear decommissioning trust liability	303		273		'		'
Deferred income taxes	886		0		'		'
Derivative instruments	279		312		'		'
Out-of-market contracts	162		180		'		'
Other non-current liabilities	510		618		'		'
Total non-current liabilities	2,746		2,047		'		'
Total Liabilities	4,970		4,745		'		'
3.625% convertible perpetual preferred stock	0		0		'		'
Total Stockholders' Equity	15,391		14,669		'		'
Total Liabilities and Stockholders' Equity	20,361		19,414		'		'
Non-Guarantor Subsidiaries	'		'		'		'
Current Assets	'		'		'		'
Cash and cash equivalents	1,110		1,258		223		85
Funds deposited by counterparties	122		140		'		'
Restricted cash	278		196		'		'
Accounts receivable-trade, net	234		254		'		'
Inventory	455		439		'		'
Derivative instruments	491		604		'		'
Deferred income taxes	'		10		'		'
Cash collateral paid in support of energy risk management activities	35		148		'		'
Renewable energy grant receivable	344		58		'		'
Prepayments and other current assets	283		-57		'		'
Total current assets	3,352		3,050		'		'
Net property, plant and equipment	10,822		10,235		'		'
Other Assets	'		'		'		'
Investment in subsidiaries	-108		-102		'		'
Equity investments in affiliates	724		633		'		'
Capital leases and notes receivable, less current portion	66		74		'		'
Goodwill	12		12		'		'
Intangible assets, net	172		177		'		'
Nuclear decommissioning trust fund	0		0		'		'
Deferred income taxes	784		1,829		'		'
Derivative instruments	307		515		'		'
Other non-current assets	239		305		'		'
Total other assets	2,196		3,443		'		'
Total assets	16,370		16,728		'		'
Current Liabilities	'		'		'		'
Current portion of long-term debt and capital leases	890		137		'		'
Accounts payable	436		584		'		'
Accounts payable — affiliate	1,973		1,421		'		'
Derivative instruments	193		271		'		'
Deferred income taxes	-264		'		'		'
Cash collateral received in support of energy risk management activities	122		140		'		'
Accrued expenses and other current liabilities	478		488		'		'
Total current liabilities	3,828		3,041		'		'
Other Liabilities	'		'		'		'
Long-term debt and capital leases	7,965		8,459		'		'
Nuclear decommissioning reserve	0		0		'		'
Nuclear decommissioning trust liability	0		0		'		'
Deferred income taxes	-836		55		'		'
Derivative instruments	96		190		'		'
Out-of-market contracts	1,026		1,082		'		'
Other non-current liabilities	631		800		'		'
Total non-current liabilities	8,882		10,586		'		'
Total Liabilities	12,710		13,627		'		'
3.625% convertible perpetual preferred stock	0		0		'		'
Total Stockholders' Equity	3,660		3,101		'		'
Total Liabilities and Stockholders' Equity	16,370		16,728		'		'
NRG Energy, Inc.	'		'		'		'
Current Assets	'		'		'		'
Cash and cash equivalents	996		751		1,376		976
Funds deposited by counterparties	0		0		'		'
Restricted cash	11		10		'		'
Accounts receivable-trade, net	0		0		'		'
Inventory	0		0		'		'
Derivative instruments	0		0		'		'
Deferred income taxes	'		199		'		'
Cash collateral paid in support of energy risk management activities	0		0		'		'
Renewable energy grant receivable	1		0		'		'
Prepayments and other current assets	-3,414		-2,518		'		'
Total current assets	-2,406		-1,558		'		'
Net property, plant and equipment	149		121		'		'
Other Assets	'		'		'		'
Investment in subsidiaries	18,218		17,655		'		'
Equity investments in affiliates	10		10		'		'
Capital leases and notes receivable, less current portion	255		531		'		'
Goodwill	0		0		'		'
Intangible assets, net	33		33		'		'
Nuclear decommissioning trust fund	0		0		'		'
Deferred income taxes	715		368		'		'
Derivative instruments	0		0		'		'
Other non-current assets	370		210		'		'
Total other assets	19,601		18,807		'		'
Total assets	17,344		17,370		'		'
Current Liabilities	'		'		'		'
Current portion of long-term debt and capital leases	20		15		'		'
Accounts payable	26		46		'		'
Accounts payable — affiliate	-1,572		-1,366		'		'
Derivative instruments	0		2		'		'
Deferred income taxes	7		'		'		'
Cash collateral received in support of energy risk management activities	0		0		'		'
Accrued expenses and other current liabilities	272		243		'		'
Total current liabilities	-1,247		-1,060		'		'
Other Liabilities	'		'		'		'
Long-term debt and capital leases	7,766		7,496		'		'
Nuclear decommissioning reserve	0		0		'		'
Nuclear decommissioning trust liability	0		0		'		'
Deferred income taxes	0		0		'		'
Derivative instruments	0		0		'		'
Out-of-market contracts	0		0		'		'
Other non-current liabilities	236		135		'		'
Total non-current liabilities	8,002		7,631		'		'
Total Liabilities	6,755		6,571		'		'
3.625% convertible perpetual preferred stock	249		249		'		'
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	3.63%		3.63%		'		'
Total Stockholders' Equity	10,340		10,550		'		'
Total Liabilities and Stockholders' Equity	17,344		17,370		'		'
Eliminations	'		'		'		'
Current Assets	'		'		'		'
Cash and cash equivalents	0	[1]	0	[1]	0	[1]	0	[1]
Funds deposited by counterparties	0	[1]	0	[1]	'		'
Restricted cash	0	[1]	0	[1]	'		'
Accounts receivable-trade, net	0	[1]	0	[1]	'		'
Inventory	0	[1]	0	[1]	'		'
Derivative instruments	-16	[1]	-18	[1]	'		'
Deferred income taxes	'		0	[1]	'		'
Cash collateral paid in support of energy risk management activities	0	[1]	0	[1]	'		'
Renewable energy grant receivable	0		0	[1]	'		'
Prepayments and other current assets	-530	[1]	10	[1]	'		'
Total current assets	-546	[1]	-8	[1]	'		'
Net property, plant and equipment	-22	[1]	-20	[1]	'		'
Other Assets	'		'		'		'
Investment in subsidiaries	-18,218	[1]	-17,797	[1]	'		'
Equity investments in affiliates	-126	[1]	0	[1]	'		'
Capital leases and notes receivable, less current portion	-245	[1]	-529	[1]	'		'
Goodwill	0	[1]	0	[1]	'		'
Intangible assets, net	-52	[1]	-52	[1]	'		'
Nuclear decommissioning trust fund	0	[1]	0	[1]	'		'
Deferred income taxes	0	[1]	0	[1]	'		'
Derivative instruments	-3	[1]	-2	[1]	'		'
Other non-current assets	0	[1]	0	[1]	'		'
Total other assets	-18,644	[1]	-18,380	[1]	'		'
Total assets	-19,212	[1]	-18,408	[1]	'		'
Current Liabilities	'		'		'		'
Current portion of long-term debt and capital leases	0	[1]	-6	[1]	'		'
Accounts payable	0	[1]	0	[1]	'		'
Accounts payable — affiliate	-407	[1]	0	[1]	'		'
Derivative instruments	-16	[1]	-18	[1]	'		'
Deferred income taxes	0	[1]	'		'		'
Cash collateral received in support of energy risk management activities	0	[1]	0	[1]	'		'
Accrued expenses and other current liabilities	0	[1]	0	[1]	'		'
Total current liabilities	-423	[1]	-24	[1]	'		'
Other Liabilities	'		'		'		'
Long-term debt and capital leases	-245	[1]	-529	[1]	'		'
Nuclear decommissioning reserve	0	[1]	0	[1]	'		'
Nuclear decommissioning trust liability	0	[1]	0	[1]	'		'
Deferred income taxes	0	[1]	0	[1]	'		'
Derivative instruments	-3	[1]	-2	[1]	'		'
Out-of-market contracts	-31	[1]	-31	[1]	'		'
Other non-current liabilities	0	[1]	0	[1]	'		'
Total non-current liabilities	-279	[1]	-562	[1]	'		'
Total Liabilities	-702	[1]	-586	[1]	'		'
3.625% convertible perpetual preferred stock	0	[1]	0	[1]	'		'
Total Stockholders' Equity	-18,510	[1]	-17,822	[1]	'		'
Total Liabilities and Stockholders' Equity	($19,212)	[1]	($18,408)	[1]	'		'
[1]	All significant intercompany transactions have been eliminated in consolidation.

Condensed_Consolidating_Financ5

Condensed Consolidating Financial Information (Details 4) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Cash Flows from Operating Activities	'		'		'		'
Net Income/(Loss)	$143		$8		($47)		$61
Adjustments to reconcile net (loss)/income to net cash provided by operating activities:	'		'		'		'
Distributions and equity in (earnings)/losses of unconsolidated affiliates and consolidated subsidiaries	'		'		23		8
Depreciation and amortization	318		239		921		703
Provision for bad debts	'		'		49		40
Amortization of nuclear fuel	'		'		27		29
Amortization of financing costs and debt discount/premiums	'		'		-22		25
Adjustment to loss and loss on debt extinguishment	'		'		-15		8
Amortization of intangibles and out-of-market contracts	'		'		75		108
Amortization of unearned equity compensation	'		'		32		27
Changes in deferred income taxes and liability for uncertain tax benefits	'		'		39		-261
Changes in nuclear decommissioning trust liability	'		'		25		25
Changes in derivative instruments	'		'		189		360
Changes in collateral deposits supporting energy risk management activities	'		'		-59		213
Cash used by changes in other working capital	'		'		-406		-285
Net Cash (Used)/Provided by Operating Activities	'		'		823		1,058
Cash Flows from Investing Activities	'		'		'		'
Intercompany loans to subsidiaries	'		'		0		0
Acquisitions of businesses, net of cash acquired	'		'		-374		-40
Capital expenditures	'		'		-1,581		-2,474
Increase in restricted cash, net	'		'		-67		-96
Increase in restricted cash - U.S. DOE projects	'		'		-20		151
Decrease/(increase) in notes receivable	'		'		-22		-22
Investments in nuclear decommissioning trust fund securities	'		'		-369		-341
Proceeds from sales of nuclear decommissioning trust fund securities	'		'		344		316
Proceeds from renewable energy grants	'		'		52		49
Payments for (Proceeds from) Productive Assets	'		'		13		137
Other	'		'		-7		-9
Net Cash (Used)/Provided by Investing Activities	'		'		-2,031		-2,329
Cash Flows from Financing Activities	'		'		'		'
Proceeds from intercompany loans	'		'		0		0
Payment of intercompany dividends	'		'		'		0
Payment of dividends to common and preferred stockholders	'		'		-113		-28
Payment for treasury stock	'		'		-25		0
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	'		'		177		-65
Contributions and sale proceeds from noncontrolling interest in subsidiaries	'		'		504		316
Proceeds from issuance of long-term debt	'		'		1,605		2,541
Proceeds from issuance of common stock	'		'		14		0
Payment of debt issuance costs	'		'		-43		-30
Payments for short and long-term debt	'		'		-868		-955
Net Cash (Used)/Provided by Financing Activities	'		'		1,251		1,779
Effect of exchange rate changes on cash and cash equivalents	'		'		-1		-3
Net (Decrease)/Increase in Cash and Cash Equivalents	'		'		42		505
Cash and Cash Equivalents at Beginning of Period	'		'		2,087		1,105
Cash and Cash Equivalents at End of Period	2,129		1,610		2,129		1,610
Guarantor Subsidiaries	'		'		'		'
Cash Flows from Operating Activities	'		'		'		'
Net Income/(Loss)	184		73		333		310
Adjustments to reconcile net (loss)/income to net cash provided by operating activities:	'		'		'		'
Depreciation and amortization	213		217		624		647
Net Cash (Used)/Provided by Operating Activities	'		'		1,334		1,942
Cash Flows from Investing Activities	'		'		'		'
Intercompany loans to subsidiaries	'		'		-1,158		-1,686
Acquisitions of businesses, net of cash acquired	'		'		0		0
Capital expenditures	'		'		-154		183
Increase in restricted cash, net	'		'		-7		2
Increase in restricted cash - U.S. DOE projects	'		'		0		0
Decrease/(increase) in notes receivable	'		'		2		0
Investments in nuclear decommissioning trust fund securities	'		'		-369		341
Proceeds from sales of nuclear decommissioning trust fund securities	'		'		344		316
Proceeds from renewable energy grants	'		'		0		3
Payments for (Proceeds from) Productive Assets	'		'		13		133
Other	'		'		7		-13
Net Cash (Used)/Provided by Investing Activities	'		'		-1,322		-1,747
Cash Flows from Financing Activities	'		'		'		'
Proceeds from intercompany loans	'		'		0		0
Payment of intercompany dividends	'		'		'		172
Payment of dividends to common and preferred stockholders	'		'		0		0
Payment for treasury stock	'		'		0		'
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	'		'		-67		65
Contributions and sale proceeds from noncontrolling interest in subsidiaries	'		'		0		0
Proceeds from issuance of long-term debt	'		'		0		9
Proceeds from issuance of common stock	'		'		0		'
Payment of debt issuance costs	'		'		0		0
Payments for short and long-term debt	'		'		0		0
Net Cash (Used)/Provided by Financing Activities	'		'		-67		-228
Effect of exchange rate changes on cash and cash equivalents	'		'		0		0
Net (Decrease)/Increase in Cash and Cash Equivalents	'		'		-55		-33
Cash and Cash Equivalents at Beginning of Period	'		'		78		44
Cash and Cash Equivalents at End of Period	23		11		23		11
Non-Guarantor Subsidiaries	'		'		'		'
Cash Flows from Operating Activities	'		'		'		'
Net Income/(Loss)	114		48		43		166
Adjustments to reconcile net (loss)/income to net cash provided by operating activities:	'		'		'		'
Depreciation and amortization	102		20		288		48
Net Cash (Used)/Provided by Operating Activities	'		'		135		177
Cash Flows from Investing Activities	'		'		'		'
Intercompany loans to subsidiaries	'		'		4		416
Acquisitions of businesses, net of cash acquired	'		'		-59		-17
Capital expenditures	'		'		-1,388		2,241
Increase in restricted cash, net	'		'		-61		94
Increase in restricted cash - U.S. DOE projects	'		'		-18		-113
Decrease/(increase) in notes receivable	'		'		-16		-20
Investments in nuclear decommissioning trust fund securities	'		'		0		0
Proceeds from sales of nuclear decommissioning trust fund securities	'		'		0		0
Proceeds from renewable energy grants	'		'		52		46
Payments for (Proceeds from) Productive Assets	'		'		0		0
Other	'		'		-1		8
Net Cash (Used)/Provided by Investing Activities	'		'		-1,487		-1,805
Cash Flows from Financing Activities	'		'		'		'
Proceeds from intercompany loans	'		'		0		0
Payment of intercompany dividends	'		'		'		6
Payment of dividends to common and preferred stockholders	'		'		0		0
Payment for treasury stock	'		'		0		'
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	'		'		244		0
Contributions and sale proceeds from noncontrolling interest in subsidiaries	'		'		504		316
Proceeds from issuance of long-term debt	'		'		1,120		1,526
Proceeds from issuance of common stock	'		'		0		'
Payment of debt issuance costs	'		'		-9		16
Payments for short and long-term debt	'		'		-654		-51
Net Cash (Used)/Provided by Financing Activities	'		'		1,205		1,769
Effect of exchange rate changes on cash and cash equivalents	'		'		-1		-3
Net (Decrease)/Increase in Cash and Cash Equivalents	'		'		-148		138
Cash and Cash Equivalents at Beginning of Period	'		'		1,258		85
Cash and Cash Equivalents at End of Period	1,110		223		1,110		223
NRG Energy, Inc.	'		'		'		'
Cash Flows from Operating Activities	'		'		'		'
Net Income/(Loss)	133		-1		-65		43
Adjustments to reconcile net (loss)/income to net cash provided by operating activities:	'		'		'		'
Depreciation and amortization	3		2		9		8
Net Cash (Used)/Provided by Operating Activities	'		'		-1,800		-883
Cash Flows from Investing Activities	'		'		'		'
Intercompany loans to subsidiaries	'		'		1,154		0
Acquisitions of businesses, net of cash acquired	'		'		-315		-23
Capital expenditures	'		'		-39		50
Increase in restricted cash, net	'		'		1		0
Increase in restricted cash - U.S. DOE projects	'		'		-2		-38
Decrease/(increase) in notes receivable	'		'		-8		-2
Investments in nuclear decommissioning trust fund securities	'		'		0		0
Proceeds from sales of nuclear decommissioning trust fund securities	'		'		0		0
Proceeds from renewable energy grants	'		'		0		0
Payments for (Proceeds from) Productive Assets	'		'		0		4
Other	'		'		-13		14
Net Cash (Used)/Provided by Investing Activities	'		'		778		-47
Cash Flows from Financing Activities	'		'		'		'
Proceeds from intercompany loans	'		'		1,154		1,270
Payment of intercompany dividends	'		'		'		0
Payment of dividends to common and preferred stockholders	'		'		-113		28
Payment for treasury stock	'		'		-25		'
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	'		'		0		0
Contributions and sale proceeds from noncontrolling interest in subsidiaries	'		'		0		0
Proceeds from issuance of long-term debt	'		'		485		1,006
Proceeds from issuance of common stock	'		'		14		'
Payment of debt issuance costs	'		'		-34		14
Payments for short and long-term debt	'		'		-214		-904
Net Cash (Used)/Provided by Financing Activities	'		'		1,267		1,330
Effect of exchange rate changes on cash and cash equivalents	'		'		0		0
Net (Decrease)/Increase in Cash and Cash Equivalents	'		'		245		400
Cash and Cash Equivalents at Beginning of Period	'		'		751		976
Cash and Cash Equivalents at End of Period	996		1,376		996		1,376
Eliminations	'		'		'		'
Cash Flows from Operating Activities	'		'		'		'
Net Income/(Loss)	-288	[1]	-112	[1]	-358	[1]	-458	[1]
Adjustments to reconcile net (loss)/income to net cash provided by operating activities:	'		'		'		'
Depreciation and amortization	0	[1]	0	[1]	0	[1]	0	[1]
Net Cash (Used)/Provided by Operating Activities	'		'		1,154	[1]	-178	[1]
Cash Flows from Investing Activities	'		'		'		'
Intercompany loans to subsidiaries	'		'		0	[1]	1,270	[1]
Acquisitions of businesses, net of cash acquired	'		'		0	[1]	0	[1]
Capital expenditures	'		'		0	[1]	0	[1]
Increase in restricted cash, net	'		'		0	[1]	0	[1]
Increase in restricted cash - U.S. DOE projects	'		'		0	[1]	0	[1]
Decrease/(increase) in notes receivable	'		'		0	[1]	0	[1]
Investments in nuclear decommissioning trust fund securities	'		'		0	[1]	0	[1]
Proceeds from sales of nuclear decommissioning trust fund securities	'		'		0	[1]	0	[1]
Proceeds from renewable energy grants	'		'		0	[1]	0	[1]
Payments for (Proceeds from) Productive Assets	'		'		0	[1]	0	[1]
Other	'		'		0	[1]	0	[1]
Net Cash (Used)/Provided by Investing Activities	'		'		0	[1]	1,270	[1]
Cash Flows from Financing Activities	'		'		'		'
Proceeds from intercompany loans	'		'		-1,154	[1]	-1,270	[1]
Payment of intercompany dividends	'		'		'		-178	[1]
Payment of dividends to common and preferred stockholders	'		'		0	[1]	0	[1]
Payment for treasury stock	'		'		0	[1]	'
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	'		'		0	[1]	0	[1]
Contributions and sale proceeds from noncontrolling interest in subsidiaries	'		'		0	[1]	0	[1]
Proceeds from issuance of long-term debt	'		'		0	[1]	0	[1]
Proceeds from issuance of common stock	'		'		0		'
Payment of debt issuance costs	'		'		0	[1]	0	[1]
Payments for short and long-term debt	'		'		0	[1]	0	[1]
Net Cash (Used)/Provided by Financing Activities	'		'		-1,154	[1]	-1,092	[1]
Effect of exchange rate changes on cash and cash equivalents	'		'		0	[1]	0	[1]
Net (Decrease)/Increase in Cash and Cash Equivalents	'		'		0	[1]	0	[1]
Cash and Cash Equivalents at Beginning of Period	'		'		0	[1]	0	[1]
Cash and Cash Equivalents at End of Period	$0	[1]	$0	[1]	$0	[1]	$0	[1]
[1]	All significant intercompany transactions have been eliminated in consolidation.