NRG Energy (NRG) 10-Q 8 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 30, 2015
Document And Entity Information [Abstract]
Entity Registrant Name	NRG ENERGY, INC.
Entity Central Index Key	1013871
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		333,494,559
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Operating Revenues
Total operating revenues	$3,826	[1]	$3,486	[2]
Operating Costs and Expenses
Cost of operations	3,062		2,737
Depreciation and amortization	395		335
Selling, general and administrative	263		222
Acquisition-related transaction and integration costs	10		12
Development activity expenses	34		19
Total operating costs and expenses	3,764		3,325
Gain on postretirement benefits curtailment and sale of assets	14		19
Operating Income	76		180
Other Income/(Expense)
Equity in (loss)/earnings of unconsolidated affiliates	-3		7
Other income, net	19		11
Loss on debt extinguishment	0		-41
Interest expense	-301		-255
Total other expense	-285		-278
Loss Before Income Taxes	-209		-98
Income tax benefit	-73		-31
Net Loss	-136		-67
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	-16		-11
Net Loss Attributable to NRG Energy, Inc.	-120		-56
Dividends for preferred shares	5		2
Loss Available for Common Stockholders	($125)		($58)
Loss per Share Attributable to NRG Energy, Inc. Common Stockholders
Weighted average number of common shares outstanding - basic and diluted	336		324
Loss per Weighted Average Common Share — Basic and Diluted	($0.37)		($0.18)
Dividends Per Common Share	$0.15		$0.12
[1]	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:$246 $— $— $— $— $33 $— $279
[2]	(b) Operating revenues include inter-segment sales and net derivative gains and losses of:$113 $2 $— $— $— $26 $— $141

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Income/(Loss) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net Loss	($136)	($67)
Other Comprehensive (Loss)/Income, net of tax
Unrealized loss on derivatives, net of income tax benefit of $6 and $3	-12	-9
Foreign currency translation adjustments, net of income tax (benefit)/expense of $(7) and $2	-11	6
Available-for-sale securities, net of income tax (benefit)/expense of $(4) and $2	-1	6
Defined benefit plans, net of tax expense of $4 and $0	7	2
Other comprehensive (loss)/income	-17	5
Comprehensive Loss	-153	-62
Less: Comprehensive loss attributable to noncontrolling interest and redeemable noncontrolling interests	29	15
Comprehensive Loss Attributable to NRG Energy, Inc.	-124	-47
Dividends for preferred shares	5	2
Comprehensive Loss Available for Common Stockholders	($129)	($49)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statement of Comprehensive Loss Income (Parenthetical) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Unrealized gain/loss on derivatives, income tax benefit	($6)	($3)
Foreign currency translation adjustments, income tax benefit	-7	2
Available-for-sale securities, income tax expense	-4	2
Defined benefit plans, income tax expense	($4)	$0

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Current Assets
Cash and cash equivalents	$2,164	$2,116
Funds deposited by counterparties	68	72
Restricted cash	443	457
Accounts receivable — trade, less allowance for doubtful accounts of $21 and $23	1,179	1,322
Inventory	1,109	1,247
Derivative instruments	2,029	2,425
Cash collateral paid in support of energy risk management activities	400	187
Deferred income taxes	188	174
Renewable energy grant receivable, net	68	135
Prepayments and other current assets	474	447
Total current assets	8,122	8,582
Property, plant and equipment, net of accumulated depreciation of $8,264 and $7,890	22,276	22,367
Other Assets
Equity investments in affiliates	772	771
Notes receivable, less current portion	67	72
Goodwill	2,520	2,574
Intangible assets, net of accumulated amortization of $1,511 and $1,402	2,491	2,567
Nuclear decommissioning trust fund	586	585
Derivative instruments	591	480
Deferred income taxes	1,484	1,406
Non-current assets held-for-sale	17	17
Other non-current assets	1,404	1,244
Total other assets	9,932	9,716
Total Assets	40,330	40,665
Current Liabilities
Current portion of long-term debt and capital leases	465	474
Accounts payable	1,045	1,060
Derivative instruments	1,884	2,054
Cash collateral received in support of energy risk management activities	68	72
Accrued expenses and other current liabilities	1,047	1,199
Total current liabilities	4,509	4,859
Other Liabilities
Long-term debt and capital leases	20,050	19,900
Nuclear decommissioning reserve	314	310
Nuclear decommissioning trust liability	328	333
Deferred income taxes	20	21
Derivative instruments	650	438
Out-of-market contracts, net of accumulated amortization of $585 and $562	1,221	1,244
Other non-current liabilities	1,549	1,574
Total non-current liabilities	24,132	23,820
Total Liabilities	28,641	28,679
2.822% convertible perpetual preferred stock	293	291
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount	19	19
Stockholders’ Equity
Common stock	4	4
Additional paid-in capital	8,362	8,327
Retained earnings	3,413	3,588
Less treasury stock, at cost — 81,865,411 and 78,843,552 shares, respectively	-2,059	-1,983
Accumulated other comprehensive loss	-191	-174
Noncontrolling interest	1,848	1,914
Total Stockholders’ Equity	11,377	11,676
Total Liabilities and Stockholders’ Equity	$40,330	$40,665

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Accounts receivable - trade, allowance for doubtful accounts	$21	$23
Property, plant and equipment, accumulated depreciation	8,261	7,890
Intangible assets, accumulated amortization	1,511	1,402
Accumulated Amortization of Out of Market Contracts	$585	$562
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	2.82%	2.82%
Treasury stock, shares (in shares)	81,865,411	78,843,552

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements Of Cash Flows (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash Flows from Operating Activities
Net Loss	($136)	($67)
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Distributions and equity in earnings of unconsolidated affiliates	32	-2
Depreciation and amortization	395	335
Provision for bad debts	15	21
Amortization of nuclear fuel	13	11
Amortization of financing costs and debt discount/premiums	-4	-5
Adjustment for debt extinguishment	0	19
Amortization of intangibles and out-of-market contracts	19	13
Amortization of unearned equity compensation	11	8
Changes in deferred income taxes and liability for uncertain tax benefits	-83	-111
Changes in nuclear decommissioning trust liability	-3	5
Changes in derivative instruments	261	525
Changes in collateral deposits supporting energy risk management activities	-213	-407
Gain on postretirement benefits curtailment and sale of assets	-14	-19
Cash used by changes in other working capital	-33	65
Net Cash Provided by Operating Activities	260	391
Cash Flows from Investing Activities
Acquisitions of businesses, net of cash acquired	-1	-218
Capital expenditures	-252	-237
(Increase)/decrease in restricted cash, net	-11	3
Decrease in restricted cash to support equity requirements for U.S. DOE funded projects	25	56
Decrease in notes receivable	5	1
Investments in nuclear decommissioning trust fund securities	-193	-188
Proceeds from the sale of nuclear decommissioning trust fund securities	196	183
Proceeds from renewable energy grants and state rebates	2	387
Proceeds from sale of assets, net of cash disposed of	0	77
Cash proceeds to fund cash grant bridge loan payment	0	57
Other	-41	3
Net Cash (Used)/Provided by Investing Activities	-270	124
Cash Flows from Financing Activities
Payment of dividends to common and preferred stockholders	-51	-41
Payment for treasury stock	-79	0
Net receipts/(payments for) from settlement of acquired derivatives that include financing elements	40	-223
Proceeds from issuance of long-term debt	248	1,564
Contributions to, net of distributions from, noncontrolling interest in subsidiaries	-25	9
Proceeds from issuance of common stock	1	3
Payment of debt issuance costs	0	-23
Payments for short and long-term debt	-94	-873
Net Cash Provided by Financing Activities	40	416
Effect of exchange rate changes on cash and cash equivalents	18	2
Net Increase in Cash and Cash Equivalents	48	933
Cash and Cash Equivalents at Beginning of Period	2,116	2,254
Cash and Cash Equivalents at End of Period	$2,164	$3,187

Basis_of_Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]	Basis of Presentation
	NRG Energy, Inc., or NRG or the Company, is a competitive power company, which produces, sells and delivers energy and energy products and services in major competitive power markets primarily in the U.S. while positioning itself as a leader in the way residential, industrial and commercial consumers think about and use energy products and services. NRG is responding to a consumer-driven change to the U.S. energy industry by offering cleaner, smarter and ultimately more portable energy while enabling personal energy choice, building on the strength of one of the nation’s largest and most diverse competitive power generation portfolios. The Company owns and operates approximately 51,000 MWs of generation; engages in the trading of wholesale energy, capacity and related products; transacts in and trades fuel and transportation services; and directly sells energy, services, and innovative, sustainable products and services to retail customers under the name “NRG” and various other retail brand names owned by NRG.
	The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with the SEC's regulations for interim financial information and with the instructions to Form 10-Q. Accordingly, they do not include all of the information and notes required by generally accepted accounting principles for complete financial statements. The following notes should be read in conjunction with the accounting policies and other disclosures as set forth in the notes to the consolidated financial statements in the Company's 2014 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 March 31, 2015, and the results of operations, comprehensive income/(loss) and cash flows for the three months ended March 31, 2015, and 2014.
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the U.S. 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.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies
	Other Cash Flow Information
	NRG’s investing activities exclude capital expenditures of $40 million which were accrued and unpaid at March 31, 2015.
	Noncontrolling Interest
	The following table reflects the changes in NRG's noncontrolling interest balance:
		(In millions)
	Balance as of December 31, 2014	$	1,914
	Sale of assets to NRG Yield, Inc.	(27		)
	Distributions to noncontrolling interest	(24		)
	Non-cash increase to noncontrolling interest	14
	Comprehensive loss attributable to noncontrolling interest	(29		)
	Balance as of March 31, 2015	$	1,848
	NRG RPV Holdco 1 LLC
	In April 2015, NRG and NRG Yield, Inc. announced the formation of a partnership that will invest in and hold operating portfolios of residential solar assets developed by NRG Home Solar, including: (i) an existing, unlevered portfolio of over 2,200 leases across nine states representing approximately 17 MW with a weighted average remaining lease term of approximately 17 years which NRG Yield, Inc. invested $26 million in April 2015; (ii) an in-development, tax equity financed portfolio of between 6,000 to 7,000 leases across at least 10 states representing approximately 48 MW with a lease term of 20 years; and (iii) an in-development tax equity financed portfolio of 5,500 to 6,500 leases representing approximately 42 MW with a lease term of 20 years. As part of the agreement, NRG will periodically monetize its residential leases through equity investments by NRG Yield, Inc. in NRG RPV Holdco 1 LLC. NRG will retain a 5% residual economic interest in the portfolio and act as managing member of the partnership. Allocations of income and cash will be 5% to NRG and 95% to NRG Yield, Inc. over the contracted life of the investments. Once NRG Yield, Inc. reaches its expected return on its investment, which is expected to be achieved consistent with the expiry of the remaining lease term, allocations of income and cash thereafter will be 95% to NRG and 5% to NRG Yield, Inc. NRG also has an option to purchase NRG Yield, Inc.'s interest at fair value after the flip date occurs. NRG Yield, Inc. has committed to invest up to an additional $150 million of cash contributions into the partnership over time, excluding the $26 million noted above.
	Redeemable Noncontrolling Interest in Subsidiaries
	Redeemable noncontrolling interest in subsidiaries represents third-party interests in the net assets under certain arrangements that the Company has entered into to finance the cost of solar energy systems under operating leases and wind facilities eligible for certain tax credits.  To the extent that the third-party has the right to redeem their interests for cash or other assets, the Company has included the noncontrolling interest attributable to the third party as a component of temporary equity in the mezzanine section of the consolidated balance sheet. During the three months ended March 31, 2015, changes in redeemable noncontrolling interest were immaterial and resulted from contributions from and allocated losses attributable to redeemable noncontrolling interests. As of March 31, 2015 and December 31, 2014, the Company's redeemable noncontrolling interest balance was $19 million.
	Gain on Postretirement Benefits Curtailment
	During the first quarter of 2015, the Company recognized a gain of $14 million related to the curtailment of certain of the Company's postretirement plans.
	Recent Accounting Developments
	ASU 2015-03 — In April 2015, the FASB issued ASU No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, or ASU No. 2015-03. The amendments of ASU No. 2015-03 were issued to reduce complexity in the balance sheet presentation of debt issuance costs. ASU No. 2015-03 requires that debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of debt liability, consistent with debt discounts or premiums. The recognition and measurement guidance for debt issuance costs are not affected by the amendments in this standard. The guidance in ASU No. 2015-03 is effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. Early adoption is permitted for financial statements that have not been previously issued. The adoption of this standard is not expected to have a material impact on the Company's balance sheets on a gross basis and will have no impact on net assets.
	ASU 2015-02 — In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis, or ASU No. 2015-02. The amendments of ASU No. 2015-02 were issued in an effort to minimize situations under previously existing guidance in which a reporting entity was required to consolidate another legal entity in which that reporting entity did not have: (1) the ability through contractual rights to act primarily on its own behalf; (2) ownership of the majority of the legal entity's voting rights; or (3) the exposure to a majority of the legal entity's economic benefits. ASU No. 2015-02 affects reporting entities that are required to evaluate whether they should consolidate certain legal entities. All legal entities are subject to reevaluation under the revised consolidation model. The guidance in ASU No. 2015-02 is effective for periods beginning after December 15, 2015. Early adoption is permitted. The Company adopted the standard effective January 1, 2015 and the adoption of this standard did not impact the Company's results of operations, cash flows or financial position.
	ASU 2014-16 — In November 2014, the FASB issued ASU No. 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share Is More Akin to Debt or to Equity, or ASU No. 2014-16. The amendments of ASU No. 2014-16 clarify how U.S. GAAP should be applied in determining whether the nature of a host contract is more akin to debt or equity and in evaluating whether the economic characteristics and risks of an embedded feature are "clearly and closely related" to its host contract. The guidance in ASU No. 2014-16 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. The Company adopted the standard effective January 1, 2015 and the adoption of this standard did not impact the Company's results of operations, cash flows or financial position.
	ASU 2014-09 — In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), or ASU No. 2014-09. The amendments of ASU No. 2014-09 complete the joint effort between the FASB and the International Accounting Standards Board, or IASB, to develop a common revenue standard for U.S. GAAP and International Financial Reporting Standards, or IFRS, and to improve financial reporting. The guidance in ASU No. 2014-09 provides that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for the goods or services provided and establishes the following steps to be applied by an entity: (1) identify the contract with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies the performance obligation. The guidance of ASU No. 2014-09 is effective for annual reporting periods beginning after December 15, 2016, including interim periods therein. Early adoption is not permitted. The Company is currently evaluating the impact of the standard on the Company's results of operations, cash flows and financial position.

Business_Acquisitions_and_Disp

Business Acquisitions and Dispositions	3 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	Business Acquisitions and Dispositions
	The Company has completed the following business acquisitions and dispositions that are material to the Company's financial statements:
	2015 Dispositions
	Sale of Assets to NRG Yield, Inc.
	On January 2, 2015, the Company sold the following facilities to NRG Yield, Inc.: Walnut Creek, the Tapestry projects (Buffalo Bear, Pinnacle and Taloga) and Laredo Ridge. NRG Yield, Inc. paid total cash consideration of $489 million, including $9 million of working capital adjustments, plus assumed project level debt of $737 million. The sale was recorded as a transfer of entities under common control and the related assets were transferred at carrying value of $405 million.
	2014 Acquisitions and Dispositions
	Sale of Sabine
	On December 2, 2014, the Company, through its subsidiaries GenOn Sabine (Delaware), Inc. and GenOn Sabine (Texas), Inc., completed the sale of its 50% interest in Sabine to Bayou Power, LLC, an affiliate of Rockland Capital, LLC. Sabine owns a 105 MW natural gas-fired cogeneration facility located in Texas. The Company received cash consideration of $35 million at closing. A gain of $18 million was recognized as a result of the transaction and recorded as a gain on sale of equity-method investments within the Company's consolidated statements of operations.
	Acquisition of Alta Wind
	On August 12, 2014, NRG Yield, Inc., through its subsidiary Yield Operating, completed the acquisition of 100% of the membership interests of Alta Wind Asset Management Holdings, LLC, Alta Wind Company, LLC, Alta Wind X Holding Company, LLC, and Alta Wind XI Holding Company, LLC, which collectively own seven wind facilities that total 947 MWs located in Tehachapi, California and a portfolio of land leases, or the Alta Wind Assets. Power generated by the Alta Wind facilities is sold to Southern California Edison under long-term power purchase agreements, with 21 years of remaining contract life for Alta I-V. The Alta X and XI power purchase agreements begin in 2016 with a term of 22 years and currently sell energy and renewable energy credits on a merchant basis.
	The purchase price of the Alta Wind Assets was $923 million, which was comprised of purchase price of $870 million and $53 million paid for working capital balances. In order to fund the purchase price of the acquisition, NRG Yield, Inc. issued 12,075,000 shares of its Class A common stock on July 29, 2014, for net proceeds of $630 million. In addition, on August 5, 2014, Yield Operating issued $500 million in aggregate principal amount at par of 5.375% senior notes due August 2024. Interest on the notes is payable semi-annually on February 15 and August 15 of each year, and commenced on February 15, 2015. The notes are senior unsecured obligations of Yield Operating and are guaranteed by NRG Yield LLC, Yield Operating’s parent company, and by certain of Yield Operating’s wholly owned subsidiaries.
	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 initial accounting for the business combination is not complete because the evaluation necessary to assess the fair values of certain net assets acquired is still in process. The provisional amounts are subject to revision until the evaluations are completed to the extent that additional information is obtained about the facts and circumstances that existed as of the acquisition date. 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. The following table summarizes the provisional amounts recognized for assets acquired and liabilities assumed as of December 31, 2014, as well as adjustments made through March 31, 2015. The purchase price of $923 million was provisionally allocated as follows:
		Acquisition Date Fair Value at December 31, 2014		Measurement period adjustments			Revised Acquisition Date
		(In millions)
	Assets
	Cash	$	22	$	—		$	22
	Current and non-current assets	49		(2		)	47
	Property, plant and equipment	1,304		6			1,310
	Intangible assets	1,177		(6		)	1,171
	Total assets acquired	2,552		(2		)	2,550
	Liabilities
	Debt	1,591		—			1,591
	Current and non-current liabilities	38		(2		)	36
	Total liabilities assumed	1,629		(2		)	1,627
	Net assets acquired	$	923	$	—		$	923
	Disposition of 50% Interest in Petra Nova Parish Holdings LLC
	On July 3, 2014, the Company, through its wholly owned subsidiary Petra Nova Holdings LLC, sold 50% of its interest in Petra Nova Parish Holdings LLC to JX Nippon Oil Exploration (EOR) Limited, JX Nippon, a wholly owned subsidiary of JX Nippon Oil & Gas Exploration Corporation.  As a result of the sale, the Company no longer has a controlling interest in and has deconsolidated Petra Nova Parish Holdings LLC as of the date of the sale. On July 7, 2014, the Company made its initial capital contribution into the partnership of $35 million, which was funded with a portion of the sale proceeds of $76 million. On March 3, 2014, Petra Nova CCS I LLC, a wholly owned subsidiary of Petra Nova Parish Holdings LLC, entered into a fixed-price agreement to build and operate a CCF at the W.A. Parish facility with a consortium of Mitsubishi Heavy Industries America, Inc. and TIC - The Industrial Company.  Notice to proceed for the construction on the CCF was issued on July 15, 2014, and commercial operation is expected in late 2016.
	Petra Nova Parish Holdings LLC also owns a 75 MW peaking unit at W.A. Parish, which achieved commercial operations on June 26, 2013. The peaking unit will be converted into a cogeneration facility to provide power and steam to the CCF.  The project is being financed by: (i) up to $167 million from a U.S. DOE CCPI grant, (ii) $250 million in loans provided by the Japan Bank for International Cooperation and Mizuho Bank, Ltd., and (iii) approximately $300 million in equity contributions from each of the Company and JX Nippon. NRG’s contribution will include investments already made during the development of the project.
	Sale of Assets to NRG Yield, Inc.
	On June 30, 2014, the Company sold the following facilities to NRG Yield, Inc.: High Desert, Kansas South, and El Segundo Energy Center. NRG Yield, Inc. paid total cash consideration of $357 million, which represents a base purchase price of $349 million and $8 million of working capital adjustments, plus assumed project level debt of approximately $612 million. The sale was recorded as a transfer of entities under common control and the related assets were transferred at carrying value of $236 million.
	Acquisition of Dominion's Competitive Electric Retail Business
	On March 31, 2014, the Company acquired the competitive retail electricity business of Dominion. The acquisition of Dominion's competitive retail electricity business increased NRG’s retail portfolio by approximately 540,000 customers in the aggregate by the end of 2014. The acquisition supports NRG's ongoing efforts to expand the Company's retail footprint in the Northeast and to grow its retail position in Texas. The Company paid approximately $192 million as cash consideration for the acquisition, including $165 million of purchase price and $27 million paid for working capital balances, which was funded by cash on hand. The purchase price was allocated to the following: $40 million to accounts receivable-trade, $64 million to customer relationships, $9 million to trade names, $14 million to current assets, $21 million to derivative assets, $47 million to current and non-current liabilities, and goodwill of $91 million of which $8 million is deductible for U.S. income tax purposes in future periods. The factors that resulted in goodwill arising from the acquisition include the revenues associated with new customers in new regions and through the synergies associated with combining a new retail business with the Company's existing retail and generation assets. The assets acquired and liabilities assumed are included within the NRG Home Retail segment. The accounting for the Dominion acquisition was completed as of March 30, 2015, at which point the provisional fair values became final with no material changes.
	EME Acquisition
	On April 1, 2014, the Company acquired substantially all of the assets of EME.  EME, through its subsidiaries and affiliates, owned or leased and operated a portfolio of approximately 8,000 MW consisting of wind energy facilities and coal- and gas-fired generating facilities. The Company paid an aggregate purchase price of $3.5 billion, which was funded through the issuance of 12,671,977 shares of NRG common stock on April 1, 2014, the issuance of $700 million in newly-issued corporate debt and cash on hand. The Company also assumed non-recourse debt of approximately $1.2 billion.
	In connection with the transaction, NRG agreed to certain conditions with the parties to the POJO sale-leaseback transaction subject to which an NRG subsidiary assumed the POJO leveraged leases and NRG guaranteed the remaining payments under each lease, which total $405 million through 2034. 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 comply with environmental regulations, as discussed further in Note 15, Environmental Matters.
	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 accounting for the EME acquisition was completed as of March 31, 2015, at which point the fair values became final. The following table summarizes the provisional amounts recognized for assets acquired and liabilities assumed as of December 31, 2014, as well as adjustments made through March 31, 2015, when the allocation became final. Measurement period adjustments primarily reflect the tax impact of the acquisition date fair values and final estimates for asset retirement obligations. The purchase price of $3.5 billion was allocated as follows:
		Acquisition Date Fair Value at December 31, 2014		Measurement period adjustments			Revised Acquisition Date
		(In millions)
	Assets
	Cash	$	1,422	$	—		$	1,422
	Current assets	724		72			796
	Property, plant and equipment	2,438		(3		)	2,435
	Intangible assets	172		—			172
	Goodwill	334		(56		)	278
	Non-current assets	773		—			773
	Total assets acquired	5,863		13			5,876
	Liabilities
	Current and non-current liabilities	629		13			642
	Out-of-market contracts and leases	159		—			159
	Long-term debt	1,249		—			1,249
	Total liabilities assumed	2,037		13			2,050
	Less: noncontrolling interest	352		—			352
	Net assets acquired	$	3,474	$	—		$	3,474

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2015
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 2014 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 March 31, 2015				As of December 31, 2014
		Carrying Amount		Fair Value		Carrying Amount		Fair Value
		(In millions)
	Assets:
	Notes receivable (a)	$	86	$	86	$	91	$	91
	Liabilities:
	Long-term debt, including current portion	$	20,509	$	20,679	$	20,366	$	20,361
	(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 2 within the fair value hierarchy. The fair value of debt securities, non publicly-traded long-term debt and certain notes receivable of the Company are based on expected future cash flows discounted at market interest rates, or current interest rates for similar instruments with equivalent credit quality and are classified as Level 3 within the fair value hierarchy.
	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 March 31, 2015
		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	$	—	$	—	$	18	$	18
	Available-for-sale securities	24		—		—		24
	Other (a)	20		—		11		31
	Nuclear trust fund investments:
	Cash and cash equivalents	5		—		—		5
	U.S. government and federal agency obligations	50		3		—		53
	Federal agency mortgage-backed securities	—		71		—		71
	Commercial mortgage-backed securities	—		24		—		24
	Corporate debt securities	—		84		—		84
	Equity securities	293		—		54		347
	Foreign government fixed income securities	—		2		—		2
	Other trust fund investments:
	U.S. government and federal agency obligations	1		—		—		1
	Derivative assets:
	Commodity contracts	998		1,358		264		2,620
	Total assets	$	1,391	$	1,542	$	347	$	3,280
	Derivative liabilities:
	Commodity contracts	$	964	$	1,142	$	230	$	2,336
	Interest rate contracts	—		198		—		198
	Total liabilities	$	964	$	1,340	$	230	$	2,534
	(a) Consists primarily of mutual funds held in a Rabbi Trust for non-qualified deferred compensation plans for certain former employees and a total return swap that does not meet the definition of a derivative.
		As of December 31, 2014
		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	$	—	$	—	$	18	$	18
	Available-for-sale securities	30		—		—		30
	Other (a)	21		—		11		32
	Nuclear trust fund investments:
	Cash and cash equivalents	14		—		—		14
	U.S. government and federal agency obligations	44		3		—		47
	Federal agency mortgage-backed securities	—		74		—		74
	Commercial mortgage-backed securities	—		25		—		25
	Corporate debt securities	—		78		—		78
	Equity securities	292		—		52		344
	Foreign government fixed income securities	—		3		—		3
	Other trust fund investments:
	U.S. government and federal agency obligations	1		—		—		1
	Derivative assets:
	Commodity contracts	1,078		1,515		309		2,902
	Interest rate contracts	—		2		—		2
	Equity contracts	—		—		1		1
Total assets	$	1,480	$	1,700	$	391	$	3,571
Derivative liabilities:
Commodity contracts	$	1,004	$	1,093	$	230	$	2,327
Interest rate contracts	—		165		—		165
Total liabilities	$	1,004	$	1,258	$	230	$	2,492
(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 months ended March 31, 2015, and 2014 between Levels 1 and 2. The following tables reconcile, for the three months ended March 31, 2015, and 2014, 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 March 31, 2015
(In millions)	Debt Securities		Other		Trust Fund Investments		Derivatives(a)			Total
Beginning balance	$	18	$	11	$	52	$	80		$	161
Total gains/(losses) — realized/unrealized:
Included in earnings	—		—		—		(55		)	(55		)
Included in nuclear decommissioning obligation	—		—		2		—			2
Purchases	—		—		—		(4		)	(4		)
Transfers into Level 3 (b)	—		—		—		15			15
Transfers out of Level 3 (b)	—		—		—		(2		)	(2		)
Ending balance as of March 31, 2015	$	18	$	11	$	54	$	34		$	117
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 March 31, 2015	$	—	$	—	$	—	(20		)	$	(20	)
(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 March 31, 2014
(In millions)	Debt Securities		Other		Trust Fund Investments		Derivatives(a)			Total
Beginning balance	$	16	$	10	$	56	$	13		$	95
Total gains/(losses) — realized/unrealized:
Included in earnings	—		1		—		16			17
Included in OCI	2		—		—		—			2
Purchases	—		—		—		(21		)	(21		)
Contracts acquired in Dominion acquisition	—		—		—		3			3
Transfers into Level 3 (b)	—		—		—		18			18
Transfers out of Level 3 (b)	—		—		—		(6		)	(6		)
Ending balance as of March 31, 2014	$	18	$	11	$	56	$	23		$	108
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 March 31, 2014	—		—		—		19			19
(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 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. 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 March 31, 2015, contracts valued with prices provided by models and other valuation techniques make up 10% of the total derivative assets and 9% 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. As of March 31, 2015, the credit reserve resulted in a $5 million increase in fair value which is composed of a $3 million gain in OCI and a $2 million gain in operating revenue and cost of operations. As of March 31, 2014, the credit reserve was not a material amount.
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 2014 Form 10-K, the following is a discussion of the concentration of credit risk for the Company's contractual obligations. Credit risk relates to the risk of loss resulting from non-performance or non-payment by counterparties pursuant to the terms of their contractual obligations. NRG is exposed to counterparty credit risk through various activities including wholesale sales, fuel purchases and retail supply arrangements, and retail customer credit risk through its retail load activities.
Counterparty Credit Risk
The Company's counterparty credit risk policies are disclosed in its 2014 Form 10-K. As of March 31, 2015, counterparty credit exposure, excluding credit risk exposure under certain long term agreements, was $842 million and NRG held collateral (cash and letters of credit) against those positions of $84 million, resulting in a net exposure of $763 million. Approximately 91% of the Company's exposure before collateral is expected to roll off by the end of 2016. 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	48	%
Utilities, energy merchants, marketers and other	32
ISOs	20
Total as of March 31, 2015	100	%
	Net Exposure (a)
Category	(% of Total)
Investment grade	96	%
Non-rated (b)	2
Non-investment grade	2
Total as of March 31, 2015	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 $290 million as of March 31, 2015. 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, Gulf Coast load obligations, wind and solar PPAs, and a coal supply agreement. As external sources or observable market quotes are not available to estimate such exposure, the Company estimates its credit exposure for these contracts based on various techniques including, but not limited to, internal models based on a fundamental analysis of the market and extrapolation of observable market data with similar characteristics. Based on these valuation techniques, as of March 31, 2015, aggregate credit risk exposure managed by NRG to these counterparties was approximately $3.3 billion, including $2.3 billion 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 and other technology and market factors, which NRG is unable to predict. In the case of the coal supply agreement, NRG holds a lien against the underlying asset which significantly reduces the risk of loss.
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 March 31, 2015, the Company believes its retail customer credit exposure was diversified across many customers and various industries, as well as government entities.

Nuclear_Decommissioning_Trust_

Nuclear Decommissioning Trust Fund	3 Months Ended
	Mar. 31, 2015
Nuclear Decommissioning Trust Fund Disclosure [Abstract]
Nuclear Decommissioning Trust Fund	Nuclear Decommissioning Trust Fund
	This footnote should be read in conjunction with the complete description under Note 6, Nuclear Decommissioning Trust Fund, to the Company's 2014 Form 10-K.
	NRG's Nuclear Decommissioning Trust Fund assets are comprised of securities classified as available-for-sale and recorded at fair value based on actively quoted market prices. NRG accounts for the Nuclear Decommissioning Trust Fund in accordance with ASC 980, Regulated Operations, because the Company's nuclear decommissioning activities are subject to approval by the PUCT with regulated rates that are designed to recover all decommissioning costs and that can be charged to and collected from the ratepayers per PUCT mandate. Since the Company is in compliance with PUCT rules and regulations regarding decommissioning trusts and the cost of decommissioning is the responsibility of the Texas ratepayers, not NRG, all realized and unrealized gains or losses (including other-than-temporary impairments) related to the Nuclear Decommissioning Trust Fund are recorded to 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 March 31, 2015							As of December 31, 2014
	(In millions, except otherwise noted)	Fair Value		Unrealized Gains		Unrealized Losses		Weighted-average Maturities (In years)	Fair Value		Unrealized Gains		Unrealized Losses		Weighted-average Maturities (In years)
	Cash and cash equivalents	$	5	$	—	$	—	—	$	14	$	—	$	—	—
	U.S. government and federal agency obligations	53		3		—		10	47		2		—		11
	Federal agency mortgage-backed securities	71		2		—		24	74		2		—		25
	Commercial mortgage-backed securities	24		—		1		30	25		—		1		30
	Corporate debt securities	84		2		—		10	78		2		1		11
	Equity securities	347		211		—		—	344		211		—		—
	Foreign government fixed income securities	2		—		—		15	3		1		—		16
	Total	$	586	$	218	$	1		$	585	$	218	$	2
	The following table summarizes proceeds from sales of available-for-sale securities and the related realized gains and losses from these sales. The cost of securities sold is determined on the specific identification method.
		Three months ended March 31,
		2015		2014
		(In millions)
	Realized gains	$	6	$	3
	Realized losses	2		1
	Proceeds from sale of securities	196		183

Accounting_for_Derivative_Inst

Accounting for Derivative Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 2015
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 2014 Form 10-K.
	Energy-Related Commodities
	As of March 31, 2015, NRG had energy-related derivative instruments extending through 2024. The Company voluntarily de-designated all remaining commodity cash flow hedges as of January 1, 2014, and prospectively marked these derivatives to market through the income statement.
	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 March 31, 2015, the Company had interest rate derivative instruments on non-recourse debt extending through 2032, most 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 category, excluding those derivatives that qualified for the NPNS exception as of March 31, 2015, and December 31, 2014. 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
			March 31, 2015				December 31, 2014
	Category	Units	(In millions)
	Emissions	Short Ton	4				2
	Coal	Short Ton	48				57
	Natural Gas	MMBtu	(35		)		(58		)
	Oil	Barrel	1				1
	Power	MWh	(52		)		(56		)
	Capacity	MW/Day	(1		)		—
	Interest	Dollars	$	3,399			$	3,440
	Equity	Shares	2				2
	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
		March 31, 2015				December 31, 2014				March 31, 2015				December 31, 2014
		(In millions)
	Derivatives designated as cash flow hedges:
	Interest rate contracts current	$	—			$	—			$	51			$	55
	Interest rate contracts long-term	—				2				97				74
	Commodity contracts current	—				—				—				—
	Commodity contracts long-term	—				—				—				—
	Total derivatives designated as cash flow hedges	—				2				148				129
	Derivatives not designated as cash flow hedges:
	Interest rate contracts current	—				—				9				8
	Interest rate contracts long-term	—				—				41				28
	Commodity contracts current	2,029				2,425				1,824				1,991
	Commodity contracts long-term	591				477				512				336
	Equity contracts long-term	—				1				—				—
	Total derivatives not designated as cash flow hedges	2,620				2,903				2,386				2,363
	Total derivatives	$	2,620			$	2,905			$	2,534			$	2,492
	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 March 31, 2015		(In millions)
	Commodity contracts:
	Derivative assets		$	2,620			$	(2,092	)		$	(64	)		$	464
	Derivative liabilities		(2,336		)		2,092				55				(189		)
	Total commodity contracts		284				—				(9		)		275
	Interest rate contracts:
	Derivative liabilities		(198		)		—				—				(198		)
	Total derivative instruments		$	86			$	—			$	(9	)		$	77
			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, 2014		(In millions)
	Commodity contracts:
	Derivative assets		$	2,902			$	(2,155	)		$	(72	)		$	675
	Derivative liabilities		(2,327		)		2,155				27				(145		)
	Total commodity contracts		575				—				(45		)		530
	Interest rate contracts:
	Derivative assets		2				(2		)		—				—
	Derivative liabilities		(165		)		2				—				(163		)
	Total interest rate contracts		(163		)		—				—				(163		)
	Equity contracts:
	Derivative assets		1				—				—				1
	Total derivative instruments		$	413			$	—			$	(45	)		$	368
Accumulated Other Comprehensive Loss
The following table summarizes the effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax:
	Three months ended March 31, 2015
	Energy Commodities				Interest Rate				Total
	(In millions)
Accumulated OCI beginning balance	$	(1	)		$	(67	)		$	(68	)
Reclassified from accumulated OCI to income:
Due to realization of previously deferred amounts	—				2				2
Mark-to-market of cash flow hedge accounting contracts	—				(18		)		(18		)
Accumulated OCI ending balance, net of $50 tax	$	(1	)		$	(83	)		$	(84	)
Losses expected to be realized from OCI during the next 12 months, net of $7 tax	$	(1	)		$	(13	)		$	(14	)
	Three months ended March 31, 2014
	Energy Commodities				Interest Rate				Total
	(In millions)
Accumulated OCI beginning balance	$	(1	)		$	(22	)		$	(23	)
Reclassified from accumulated OCI to income:
Due to realization of previously deferred amounts	—				(1		)		(1		)
Mark-to-market of cash flow hedge accounting contracts	—				(8		)		(8		)
Accumulated OCI ending balance, net of $17 tax	$	(1	)		$	(31	)		$	(32	)
Losses expected to be realized from OCI during the next 12 months, net of $7 tax	$	(1	)		$	(13	)		$	(14	)
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. There was no ineffectiveness for the three months ended March 31, 2015 and 2014.
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 March 31,
	2015				2014
Unrealized mark-to-market results	(In millions)
Reversal of previously recognized unrealized (gains)/losses on settled positions related to economic hedges	$	(114	)		$	3
Reversal of acquired gain positions related to economic hedges	(26		)		(78		)
Net unrealized losses on open positions related to economic hedges	(138		)		(193		)
Total unrealized mark-to-market losses for economic hedging activities	(278		)		(268		)
Reversal of previously recognized unrealized gains on settled positions related to trading activity	(21		)		—
Reversal of acquired gain positions related to trading activity	(7		)		(1		)
Net unrealized gains on open positions related to trading activity	6				16
Total unrealized mark-to-market (losses)/gains for trading activity	(22		)		15
Total unrealized losses	$	(300	)		$	(253	)
	Three months ended March 31,
	2015				2014
	(In millions)
Unrealized losses included in operating revenues	$	(109	)		$	(316	)
Unrealized (losses)/gains included in cost of operations	(191		)		63
Total impact to statement of operations — energy commodities	$	(300	)		$	(253	)
Total impact to statement of operations — interest rate contracts	$	(14	)		$	(4	)
The reversals of acquired gain or loss positions were valued based upon the forward prices on the acquisition date. The roll-off amounts were offset by realized gains or losses at the settled prices and are reflected in revenue or cost of operations during the same period.
For the three months ended March 31, 2015, the $138 million unrealized loss from open economic hedge positions was primarily the result of a decrease in value of forward purchases of coal due to decreases in coal prices.
For the three months ended March 31, 2014, the $193 million unrealized loss from open economic hedge positions was primarily the result of a decrease in value of forward sales of natural gas and electricity due to an increase in forward natural gas and power prices.
Credit Risk Related Contingent Features
Certain of the Company's hedging agreements contain provisions that require the Company to post additional collateral if the counterparty determines that there has been deterioration in credit quality, generally termed “adequate assurance” under the agreements, or 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 March 31, 2015, was $131 million. The collateral required for contracts with credit rating contingent features as of March 31, 2015, 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 $8 million as of March 31, 2015.
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	3 Months Ended
	Mar. 31, 2015
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 12, Debt and Capital Leases, to the Company's 2014 Form 10-K. Long-term debt and capital leases consisted of the following:
	(In millions, except rates)	March 31, 2015		December 31, 2014		Current interest rate % (a)
	Recourse debt:
	Senior notes, due 2018	$	1,130	$	1,130	7.625
	Senior notes, due 2020	1,063		1,063		8.25
	Senior notes, due 2021	1,128		1,128		7.875
	Senior notes, due 2022	1,100		1,100		6.25
	Senior notes, due 2023	990		990		6.625
	Senior notes, due 2024	1,000		1,000		6.25
	Term loan facility, due 2018	1,978		1,983		L+2.00
	Tax-exempt bonds	434		406		4.125 - 6.00
	Subtotal NRG recourse debt	8,823		8,800
	Non-recourse debt:
	GenOn senior notes	2,121		2,133		7.875 - 9.875
	GenOn Americas Generation senior notes	926		929		8.500 - 9.125
	GenOn Other	60		60		various
	Subtotal GenOn debt (non-recourse to NRG)	3,107		3,122
	NRG Yield Operating LLC Senior Notes, due 2024	500		500		5.375
	NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2019	195		—		L+2.25
	NRG Yield, Inc. Convertible Senior Notes, due 2019	327		326		3.5
	NRG West Holdings LLC, due 2023 (El Segundo Energy Center)	484		506		L+2.25 - L+2.875
	NRG Marsh Landing, due 2017 and 2023	457		464		L+1.75 - L+1.875
	Alta Wind I - V lease financing arrangements, due 2034 and 2035	1,036		1,036		5.696-7.015
	Alta Wind X, due 2021	300		300		L+2.00
	Alta Wind XI, due 2021	191		191		L+2.00
	Walnut Creek, term loans due 2023	384		391		L+1.625
	Tapestry Wind LLC, due 2021	188		192		L+1.625
	Laredo Ridge Wind LLC, due 2026	107		108		L+1.875
	NRG Solar Alpine LLC, due 2022	162		163		L+1.750
	NRG Energy Center Minneapolis LLC, due 2017 and 2025	119		121		5.95 - 7.25
	NRG Yield - other	487		489		various
	Subtotal NRG Yield debt (non-recourse to NRG)	4,937		4,787
	Ivanpah Financing, due 2033 and 2038	1,179		1,187		2.285 - 4.256
	Agua Caliente Solar LLC, due 2037	907		898		2.395 - 3.633
	CVSR High Plains Ranch II LLC, due 2037	802		815		2.339 - 3.775
	Viento Funding II, Inc., due 2023	196		196		L+2.75
	NRG Peaker Finance Co. LLC, bonds due 2019	101		100		L+1.07
	Cedro Hill Wind LLC, due 2025	108		111		L+3.125
	NRG - other	349		350		various
	Subtotal NRG non-recourse debt	3,642		3,657
	Subtotal non-recourse debt (including GenOn and NRG Yield)	11,686		11,566
	Subtotal long-term debt (including current maturities)	20,509		20,366
	Capital leases:
	Chalk Point capital lease, due 2015	3		5		8.19
	Other	3		3		various
	Subtotal long-term debt and capital leases (including current maturities)	20,515		20,374
	Less current maturities	465		474
	Total long-term debt and capital leases	$	20,050	$	19,900
	(a) As of March 31, 2015, L+ equals 3 month LIBOR plus x%, with the exception of the Viento Funding II term loan which is 6 month LIBOR plus x% and the NRG West Holdings LLC term loan, NRG Marsh Landing term loan, Walnut Creek term loan, and NRG Yield Operating LLC Revolving Credit facility which are 1 month LIBOR plus x%.
	NRG Recourse Debt
	Senior Notes
	Issuance of 2022 Senior Notes
	On January 27, 2014, NRG issued $1.1 billion in aggregate principal amount at par of 6.25% senior notes due 2022. The notes are senior unsecured obligations of NRG and are guaranteed by certain of its subsidiaries. Interest is payable semi-annually beginning on July 15, 2014, until the maturity date of July 15, 2022. The proceeds were utilized to redeem the 8.5% and 7.625% 2019 Senior Notes, as described below, and to fund the acquisition of EME.
	Redemptions of 8.5% and 7.625% 2019 Senior Notes
	On February 10, 2014, the Company redeemed $308 million of its 8.5% 2019 Senior Notes and $91 million of its 7.625% 2019 Senior Notes through a tender offer, at an average early redemption percentage of 106.992% and 105.500%, respectively. A $33 million loss on debt extinguishment of the 8.5% and 7.625% 2019 Senior Notes was recorded during the three months ended March 31, 2014, primarily consisting of the premiums paid on the redemption and the write-off of previously deferred financing costs.
	NRG Non-Recourse Debt
	The Company has non-recourse debt that is secured by acquired or developed projects that are held in several of its subsidiaries.  In the event of a bankruptcy, receivership, liquidation or similar event involving a subsidiary, the assets of such subsidiary would be used to satisfy claims of creditors of the subsidiary, including liabilities under the non-recourse debt associated with such subsidiaries, rather than the creditors of NRG. As described in Note 3, Business Acquisitions and Dispositions, through the Company's acquisitions of EME on April 1, 2014 and Alta Wind on August 12, 2014, the Company acquired approximately $1.2 billion and $1.6 billion of non-recourse debt respectively.
	High Lonesome Mesa Facility
	Prior to the Company's acquisition of EME, an intercompany tax credit agreement related to the High Lonesome Mesa facility was terminated. The termination resulted in an event of default under the project financing arrangement. As a result, the balance under the project financing arrangement is classified as current and the lender can request repayment at any time. The facility is secured by the assets of High Lonesome Mesa and is non-recourse to NRG.
	NRG Yield, Inc. Convertible Notes
	During the first quarter of 2014, NRG Yield, Inc. closed on its offering of $345 million aggregate principal amount of 3.50% Convertible Senior Notes due 2019, or the NRG Yield Convertible Notes. The NRG Yield Convertible Notes are convertible, under certain circumstances, into NRG Yield, Inc. Class A common stock, cash or a combination thereof at an initial conversion price of $46.55 per Class A common share, which is equivalent to an initial conversion rate of approximately 21.4822 shares of Class A common stock per $1,000 principal amount of NRG Yield Convertible Notes. Interest on the NRG Yield Convertible Notes is payable semi-annually in arrears on February 1 and August 1 of each year, commencing on August 1, 2014. The NRG Yield Convertible Notes mature on February 1, 2019, unless earlier repurchased or converted in accordance with their terms. Prior to the close of business on the business day immediately preceding August 1, 2018, the NRG Yield Convertible Notes will be convertible only upon the occurrence of certain events and during certain periods, and thereafter, at any time until the close of business on the second scheduled trading day immediately preceding the maturity date. The notes are accounted for in accordance with ASC 470-20. Under ASC 470-20, issuers of convertible debt instruments that may be settled in cash upon conversion, including partial cash settlement, are required to separately account for the liability (debt) and equity (conversion option) components. The equity component, the $23 million conversion option value, was recorded to NRG's noncontrolling interest for NRG Yield, Inc. with the offset to debt discount. The debt discount will be amortized to interest expense over the term of the notes.
	NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility
	NRG Yield LLC and Yield Operating entered into a senior secured revolving credit facility, which provides a revolving line of credit of $60 million. On April 25, 2014, NRG Yield LLC and Yield Operating amended the revolving credit facility to increase the available line of credit to $450 million and extend its maturity to April 2019. The revolving credit facility can be used for cash or for the issuance of letters of credit. On January 2, 2015, NRG Yield borrowed $210 million under the revolving credit facility to fund the acquisition of Walnut Creek, Laredo Ridge and the Tapestry projects. On February 2, 2015, NRG Yield made an optional repayment of $15 million of principal. In addition, there were $36 million of letters of credit issued under the revolving credit facility as of March 31, 2015.
Peakers
On February 21, 2014, NRG Peaker Finance Company LLC elected to redeem approximately $30 million of the outstanding bonds at a redemption price equal to the principal amount plus a redemption premium, accrued and unpaid interest, swap breakage, and other fees, totaling approximately $35 million in connection with the removal of Bayou Cove Peaking Power LLC from the peaker financing collateral package, which also involved limited commitments for certain repairs on other assets that were funded concurrently with the December 10, 2013, debt service payment. On March 3, 2014, Bayou Cove Peaking Power LLC sold Bayou Cove Unit 1, which the Company continues to manage and operate.

Variable_Interest_Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2015
Variable Interest Entities Disclosure [Abstract]
Variable Interest Entity	Variable Interest Entities, or VIEs
	Entities that are not Consolidated
	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 consolidated subsidiary, Yield Operating, the Company owns a 50% interest in GenConn, 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 $112 million as of March 31, 2015.
	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 $81 million as of March 31, 2015.
	Entities that are Consolidated
	Capistrano Wind Partners — Through the acquisition of EME, the Company has a controlling financial interest in Capistrano Wind Partners, whose Class B preferred equity interest are held by outside investors. Capistrano Wind Partners holds 100% ownership in five projects generating 411 MW of wind capacity. The five wind projects include Cedro Hill located in Texas, Mountain Wind Power I, located in Wyoming, Mountain Wind Power II located in Wyoming, Crofton Bluffs located in Nebraska, and Broken Bow I located in Nebraska.
	Under the terms of the Capistrano Wind Partners formation documents, the holders of the Class B preferred equity interests receive 100% of the cash available for distribution, up to a scheduled amount to target a certain return and thereafter cash distributions are shared. The Company retains indirect beneficial ownership of the wind projects and retains responsibilities for managing the operations of Capistrano Wind Partners. Accordingly, the Company consolidates these projects. The Company does not consolidate Capistrano Wind Partners for tax purposes.
	The summarized financial information for Capistrano Wind Holdings consisted of the following:
	(In millions)	March 31, 2015
	Current assets	$	28
	Net property, plant and equipment	578
	Other long-term assets	137
	Total assets	743
	Current liabilities	36
	Long-term debt	180
	Other long-term liabilities	154
	Total liabilities	370
	Noncontrolling interests	348
	Net assets less noncontrolling interests	$	25

Changes_in_Capital_Structure

Changes in Capital Structure	3 Months Ended
	Mar. 31, 2015
Changes in Capital Structure Disclosure [Abstract]
Changes in Capital Structure	Changes in Capital Structure
	As of March 31, 2015, and December 31, 2014, the Company had 500,000,000 shares of common stock authorized. The following table reflects the changes in NRG's common stock issued and outstanding:
		Issued		Treasury			Outstanding
	Balance as of December 31, 2014	415,506,176		(78,843,552	)		336,662,624
	Shares issued under LTIPs	1,176,486		—			1,176,486
	Shares issued under ESPP	—		124,625			124,625
	Shares repurchased under Capital Allocation Program	—		(3,146,484	)		(3,146,484	)
	Balance as of March 31, 2015	416,682,662		(81,865,411	)		334,817,251
	Employee Stock Purchase Plan
	As of March 31, 2015, there were 1,435,427 shares of treasury stock available for issuance under the ESPP.
	NRG Common Stock Dividends
	The following table lists the dividends paid during the three months ended March 31, 2015:
		First Quarter 2015
	Dividends per Common Share	$	0.145
	On April 20, 2015, NRG declared a quarterly dividend on the Company's common stock of $0.145 per share, payable May 15, 2015, to stockholders of record as of May 1, 2015, representing $0.58 on an annualized basis.
	The Company's common stock dividends are subject to available capital, market conditions, and compliance with associated laws, regulations and other contractual obligations.
	2015 Capital Allocation Program
	In December 2014, the Company was authorized to repurchase $100 million of its common stock under the 2015 Capital Allocation Program. In March 2015, the Company was authorized to repurchase an additional $100 million of its common stock under the 2015 Capital Allocation Program, for a total share repurchase of $200 million. In addition, in the second quarter of 2015, the Company's board of directors authorized the repurchase of an additional $81 million of the Company's common stock.
	The following table reflects the repurchases made under the 2015 Capital Allocation Program:
			Total number of shares purchased		Average price paid per share (a)				Amounts paid for shares purchased  (in millions) (a)
	2015 Capital Allocation Program
	Dec-14		1,624,360		$	26.95			$	44
	Jan-15		1,755,976		25.19				44
	Feb-15		468,854		25.46				12
	Mar-15		921,654		24.92				23
	Total Repurchases - First Quarter 2015		3,146,484						79
	Apr-15		1,328,329		24.47				33
	Total Repurchases under 2015 Capital Allocation Program		6,099,173		—				$	156
	(a) The average price paid per share and amounts paid for shares purchased excludes the commissions of $0.015 per share paid in connection with the share repurchase.

Earnings_Per_Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	Loss Per Share
	Basic loss per common share is computed by dividing net 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 loss per share is computed in a manner consistent with that of basic loss per share while giving effect to all potentially dilutive common shares that were outstanding during the period. The reconciliation of NRG's basic and diluted loss per share is shown in the following table:
		Three months ended March 31,
	(In millions, except per share data)	2015				2014
	Basic and diluted loss per share attributable to NRG Energy, Inc. common stockholders
	Net loss attributable to NRG Energy, Inc.	$	(120	)		$	(56	)
	Dividends for preferred shares	5				2
	Loss available for common stockholders	$	(125	)		$	(58	)
	Weighted average number of common shares outstanding - basic and diluted	336				324
	Loss per weighted average common share — basic and diluted	$	(0.37	)		$	(0.18	)
	The following table summarizes NRG’s outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company’s diluted loss per share:
		Three months ended March 31,
	(In millions of shares)	2015			2014
	Equity compensation plans	7			8
	Embedded derivative of 2.822% redeemable perpetual preferred stock(a)	16			16
	Total	23			24
	(a) As of March 31, 2014, the redeemable perpetual preferred stock had an interest rate of 3.625%.

Segment_Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2015
Segment Reporting Disclosure [Abstract]
Segment Reporting	Segment Reporting
	Effective in December 2014, 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 segregated as follows: NRG Business, which includes conventional power generation, the carbon capture business and energy services; NRG Home, which includes NRG Home Retail, consisting of residential retail services and products, and NRG Home Solar, which includes the installation and leasing of residential solar systems and the sale of solar energy services; NRG Renew, which includes solar and wind assets, excluding those in the NRG Yield segment; NRG Yield; and corporate activities.  NRG Yield includes certain of the Company's contracted generation assets. On January 2, 2015, NRG Yield, Inc. acquired three projects from the Company: Walnut Creek formerly in the NRG Business segment, the Tapestry projects (Buffalo Bear, Pinnacle and Taloga) and Laredo Ridge, both formerly in the NRG Renew segment. As the transaction was accounted for as a transfer of entities under common control, all historical periods have been recast to reflect this change. The Company's corporate segment includes international business and electric vehicle services. Intersegment sales are accounted for at market.
					NRG Home
	(In millions)	NRG Business(a)			Retail(a)		Solar(a)			NRG Renew(a)			NRG Yield(a)			Corporate(a)			Eliminations			Total
	Three months ended March 31, 2015	(in millions)
	Operating revenues(a)	$	2,506		$	1,311	$	5		$	110		$	180		$	(7	)	$	(279	)	$	3,826
	Depreciation and amortization	233			30		6			65			54			7			—			395
	Equity in (loss)/earnings of unconsolidated affiliates	(4		)	—		—			—			1			(1		)	1			(3		)
	Income/(loss) before income taxes	29			104		(45		)	(61		)	(20		)	(217		)	1			(209		)
	Net income/(loss) attributable to NRG Energy, Inc.	$	29		$	104	$	(45	)	$	(50	)	$	(11	)	$	(142	)	$	(5	)	(120		)
	Total assets as of March 31, 2015	$	28,744		$	6,270	$	178		$	7,155		$	6,595		$	31,493		$	(40,105	)	$	40,330
	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	246		$	—	$	—		$	—		$	—		$	33		$	—		$	279
					NRG Home
	(In millions)	NRG Business(b)			Retail(b)		Solar(b)			NRG Renew(b)(c)			NRG Yield(b)			Corporate(b)(c)			Eliminations			Total
	Three months ended March 31, 2014	(in millions)
	Operating revenues(b)	$	2,346		$	1,082	$	2		$	53		$	140		$	4		$	(141	)	$	3,486
	Depreciation and amortization	225			30		1			49			24			6			—			335
	Equity in earnings/(loss) of unconsolidated affiliates	5			—		—			(3		)	1			2			2			7
	(Loss)/income before income taxes	(6		)	185		(2		)	(65		)	29			(239		)	—			(98		)
	Net (loss)/income attributable to NRG Energy, Inc.	$	(6	)	$	185	$	(2	)	$	(48	)	$	22		$	(209	)	$	2		(56		)
	(b) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	113		$	2	$	—		$	—		$	—		$	26		$	—		$	141
	(c) Includes loss on debt extinguishment of:	$	—		$	—	$	—		$	(1	)	$	—		$	(40	)	$	—		$	(41	)

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Effective Tax Rate
	The income tax provision consisted of the following:
		Three months ended March 31,
	(In millions except otherwise noted)	2015			2014
	Loss before income taxes	$	(209	)	$	(98	)
	Income tax benefit	(73		)	(31		)
	Effective tax rate	34.9		%	31.6		%
	For the three months ended March 31, 2015, NRG's overall effective tax rate was different than the statutory rate of 35% primarily due to the impact of production tax credits generated from our wind assets partially offset by non-taxable equity earnings and tax expense attributable to consolidated partnerships.
	For the three months ended March 31, 2014, NRG's overall effective tax rate was different than the statutory rate of 35% primarily due to the impact of non-taxable equity earnings, production tax credits and the impact of state and local income taxes.
	Uncertain Tax Benefits
	As of March 31, 2015, NRG has recorded a non-current tax liability of $55 million for uncertain tax benefits from positions taken on various state income tax returns, including accrued interest. For the three months ended March 31, 2015, NRG accrued an insignificant amount of interest relating to the uncertain tax benefits. As of March 31, 2015, NRG had cumulative interest and penalties related to these uncertain tax benefits of $6 million . The Company recognizes interest and penalties related to uncertain tax benefits in income tax expense.
	NRG is subject to examination by taxing authorities for income tax returns filed in the U.S. federal jurisdiction and various state and foreign jurisdictions including operations located in Australia. The Company is not subject to U.S. federal income tax examinations for years prior to 2011. With few exceptions, state and local income tax examinations are no longer open for years before 2009. 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	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	This footnote should be read in conjunction with the complete description under Note 22, Commitments and Contingencies, to the Company's 2014 Form 10-K.
	Commitments
	First Lien Structure
	NRG has granted first liens to certain counterparties on a substantial portion of the Company's assets, excluding assets acquired in the GenOn and EME (including Midwest Generation) acquisitions, assets held by NRG Yield, Inc. and NRG's assets that have project-level financing, to reduce the amount of cash collateral and letters of credit that it would otherwise be required to post from time to time to support its obligations under out-of-the-money hedge agreements for forward sales of power or MWh equivalents. The Company's lien counterparties may have a claim on NRG's assets to the extent market prices exceed the hedged price. As of March 31, 2015, hedges under the first liens were in-the-money for NRG on a counterparty aggregate basis.
	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.
	Midwest Generation Asbestos Liabilities — The Company, through its subsidiary, Midwest Generation, may be subject to potential asbestos liabilities as a result of its acquisition of EME. The Company is currently analyzing the scope of potential liability as it may relate to Midwest Generation. The Company believes that it has established an adequate reserve to deal with these cases.
	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 Mirant's 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 Mirant's 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 several lawsuits, certain 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 was handling four of the five cases, granted the defendants' motion for summary judgment and dismissed all claims against GenOn in those cases. The plaintiffs appealed to the U.S. Court of Appeals for the Ninth Circuit which reversed the decision of the District Court. On August 26, 2013, GenOn along with the other defendants in the lawsuit filed a petition for a writ of certiorari to the U.S. Supreme Court challenging the Court of Appeals' decision. On July 1, 2014, the U.S. Supreme Court granted the petition. On April 21, 2015, the U.S. Supreme Court affirmed the Ninth Circuit’s holding that plaintiffs’ state antitrust law claims are not field-preempted.  The U.S. Supreme Court left open whether the claims were preempted on the basis of conflict preemption and directed that the case be sent to the U.S. District Court for the District of Nevada for further proceedings.
	In September 2012, the State of Nevada Supreme Court, which was 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 a writ of certiorari to the U.S. Supreme Court. In June 2013, the U.S. Supreme Court denied the petition for a writ of certiorari, thereby ending one of the five lawsuits. GenOn has agreed to indemnify CenterPoint against certain losses relating to these lawsuits.
	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 District 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 Court of Appeals reversed the decision of the District Court. On September 3, 2013, the Company filed a petition for rehearing with the Court of Appeals which was subsequently denied. In February 2014, the Company filed a petition for a writ of certiorari to the U.S. Supreme Court seeking review and reversal of the Court of Appeals' decision. On June 2, 2014, the U.S. Supreme Court denied the petition for a writ of certiorari. Following the U.S. Supreme Court's denial of GenOn’s petition for a writ of certiorari, the case continued to be litigated before the U.S. District Court for the Western District of Pennsylvania. After briefing by the parties on GenOn's motion to strike class allegations in the complaint, the court granted GenOn's motion, but allowed the plaintiffs the opportunity to re-file their complaint. On February 3, 2015, plaintiffs sought leave to file an amended complaint, which the Company is contesting.
	Energy Plus Holdings — On August 7, 2012, Energy Plus Holdings received a subpoena from the NYAG which generally sought information and business records related to Energy Plus Holdings' sales, marketing and business practices. Energy Plus Holdings provided documents and information to the NYAG. Energy Plus Holdings continues to cooperate and discuss a resolution of these issues with the NYAG.
	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 GenOn Mid-Atlantic 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 GenOn Mid-Atlantic a similar letter with respect to the Chalk Point and Dickerson generating facilities, threatening to sue within 60 days if the generating facilities were not brought 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 CWA and Maryland environmental laws related to water. The lawsuit is ongoing and seeks injunctive relief and civil penalties in excess of $100,000. The Company does not expect the resolution of this matter to have a material impact on the Company's consolidated financial position, results of operations, or cash flows.
	Midwest Generation New Source Review Litigation — In August 2009, the EPA and the Illinois Attorney General, or the Government Plaintiffs, filed a complaint, or the Governments’ Complaint, in the U.S. District Court for the Northern District of Illinois alleging violations of CAA PSD requirements by Midwest Generation arising from maintenance, repair or replacement projects at six Illinois coal-fired electric generating stations performed by Midwest Generation or ComEd, a prior owner of the stations, including alleged failures to obtain PSD construction permits and to comply with BACT requirements. The Government Plaintiffs also alleged violations of opacity and PM standards at the Midwest Generation plants. Finally, the Government Plaintiffs alleged that Midwest Generation violated certain operating permit requirements under Title V of the CAA allegedly arising from such claimed PSD, opacity and PM emission violations. In addition to seeking penalties of up to $37,500 per violation, per day, the complaint seeks an injunction ordering Midwest Generation to install controls sufficient to meet BACT emission rates at the units subject to the complaint and other remedies, which could go well beyond the requirements of the CPS. Several environmental groups intervened as plaintiffs in this litigation and filed a complaint, or the Intervenors’ Complaint, which alleged opacity, PM and related Title V violations. Midwest Generation filed a motion to dismiss nine of the ten PSD counts in the Governments’ Complaint, and to dismiss the tenth PSD count to the extent the Governments’ Complaint sought civil penalties for that count. The trial court granted the motion in March 2010.
	In June 2010, the Government Plaintiffs and Intervenors each filed an amended complaint. The Governments’ Amended Complaint again alleged that Midwest Generation violated PSD (based upon the same projects as alleged in their original complaint, but adding allegations that the Company was liable as the “successor” to ComEd), Title V and opacity and PM standards. It named EME and ComEd as additional defendants and alleged PSD violations (again, premised on the same projects) against them. The Intervenors’ Amended Complaint named only Midwest Generation as a defendant and alleged Title V and opacity/PM violations, as well as one of the ten PSD violations alleged in the Governments’ Amended Complaint. Midwest Generation again moved to dismiss all but one of the Government Plaintiffs’ PSD claims and the related Title V claims. Midwest Generation also filed a motion to dismiss the PSD claim in the Intervenors’ Amended Complaint and the related Title V claims. In March 2011, the trial court granted Midwest Generation’s partial motion to dismiss the Government Plaintiffs’ PSD claims. The trial court denied Midwest Generation’s motion to dismiss the PSD claim asserted in the Intervenors’ Amended Complaint, but noted that the plaintiffs would be required to convince the court that the statute of limitations should be equitably tolled. The trial court did not address other counts in the amended complaints that allege violations of opacity and PM emission limitations under the Illinois State Implementation Plan and related Title V claims. The trial court also granted the motions to dismiss the PSD claims asserted against EME and ComEd.
	Following the trial court ruling, the Government Plaintiffs appealed the trial court’s dismissals of their PSD claims, including the dismissal of nine of the ten PSD claims against Midwest Generation and of the PSD claims against the other defendants. Those PSD claim dismissals were affirmed by the U.S. Court of Appeals for the Seventh Circuit in July 2013. In addition, in 2012, all but one of the environmental groups that had intervened in the case dismissed their claims without prejudice. As a result, only one environmental group remains a plaintiff intervenor in the case. The Company does not expect the resolution of this matter to have a material impact on the Company’s consolidated financial position, results of operations or cash flows.

Regulatory_Matters

Regulatory Matters	3 Months Ended
	Mar. 31, 2015
Regulatory Matters Disclosure [Abstract]
Regulatory Matters	Regulatory Matters
	This footnote should be read in conjunction with the complete description under Note 23, Regulatory Matters, to the Company's 2014 Form 10-K.
	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.
	National
	Court Rejects FERC's Jurisdiction Over Demand Response — On May 23, 2014, the U.S. Court of Appeals for the District of Columbia Circuit vacated FERC’s rules (known as Order No. 745) that allowed demand response resources to participate in FERC-jurisdictional energy markets. The Court of Appeals held that the Federal Power Act does not authorize FERC to exercise jurisdiction over demand response and that instead demand response is part of the retail market over which the states have jurisdiction. The specific order being challenged related to energy market compensation, but this ruling also calls into question whether demand response will be permitted to participate in the capacity markets in the future. Parties including the U.S. Solicitor General have filed petitions for a writ of certiorari with the U.S. Supreme Court. On May 4, 2015, the U.S. Supreme Court granted certiorari on two questions: first, on whether the FPA gives FERC jurisdiction over demand response, and second, whether FERC’s Order No. 745 correctly determined the level of compensation paid to generators participating in the energy markets. The eventual outcome of this proceeding could result in refunds of payments made for non-jurisdictional services and resettlement of wholesale markets, but it is not possible to predict the outcome or estimate the impact on the Company at this time.
	East Region
	Montgomery County Station Power Tax — On December 20, 2013, the Company received a letter from Montgomery County, Maryland requesting payment of an energy tax for the consumption of station power at the Dickerson Facility over the previous three years.  Montgomery County seeks payment in the amount of $22 million, which includes tax, interest and penalties.  The Company is disputing the applicability of the tax. On December 17, 2014, the Maryland Tax Court heard oral arguments from the parties. Subsequently, post hearing briefs were filed. The decision is pending.

Environmental_Matters

Environmental Matters	3 Months Ended
	Mar. 31, 2015
Environmental Matters Disclosure [Abstract]
Environmental Matters	Environmental Matters
	This footnote should be read in conjunction with the complete description under Note 24, Environmental Matters, to the Company's 2014 Form 10-K.
	NRG is subject to a wide range of environmental laws in the development, construction, ownership and operation of projects. These laws generally require that governmental permits and approvals be obtained before construction and during operation of power plants. NRG is also subject to laws and regulations surrounding the protection of wildlife, including migratory birds, eagles and threatened and endangered species. Environmental laws 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 GHG, as well as combustion byproducts, water discharge and use, and threatened and endangered species. In general, future laws are expected to require the addition of emissions controls or other environmental controls or to impose certain restrictions on the operations of the Company's facilities, which could have a material effect on the Company's operations.
	The EPA finalized CSAPR in 2011, which was intended to replace CAIR in January 2012. In December 2011, the U.S. Court of Appeals for the District of Columbia Circuit stayed the implementation of CSAPR and then issued an opinion in August 2012 vacating CSAPR and keeping CAIR in place until the EPA could replace it. On April 29, 2014, the U.S. Supreme Court reversed and remanded the D.C. Circuit's decision. In October 2014, the D.C. Circuit lifted the stay of CSAPR. In response, the EPA issued an interim final rule in November 2014 to amend the CSAPR compliance dates. Accordingly, CSAPR replaced CAIR on January 1, 2015. On February 25, 2015, the D.C. Circuit held oral argument regarding several unresolved legal issues and the Company expects a decision in the second quarter of 2015. While NRG cannot predict the final outcome of the ongoing litigation, the Company believes its investment in pollution controls and cleaner technologies coupled with planned plant retirements should leave the fleet well positioned for compliance.
	In December 2014, the EPA proposed making the NAAQS for ozone more stringent. The EPA anticipates promulgating a more stringent ozone NAAQS by October 2015. A more stringent NAAQS would obligate the states to develop plans to reduce NOx (an ozone precursor), which might affect some of the Company's units.
	In February 2012, the EPA promulgated standards to control emissions of HAPs from coal and oil-fired electric generating units. The rule established limits for mercury, non-mercury metals, certain organics and acid gases, which limits must be met beginning in April 2015 (with some units getting a 1-year extension). In November 2014, the U.S. Supreme Court agreed to review the D.C. Circuit decision that denied the petitions seeking to vacate MATS but the review is limited to whether the EPA unreasonably refused to consider costs in determining whether it is appropriate to regulate HAPs emitted by electric generating units. Oral argument in the U.S. Supreme Court occurred in March 2015, and the Company expects a decision in the second quarter of 2015.
	In January 2014, the EPA re-proposed the NSPS for CO2 emissions from new fossil-fuel-fired electric generating units that had been previously proposed in April 2012. The re-proposed standards are 1,000 pounds of CO2 per MWh for large gas units and 1,100 pounds of CO2 per MWh for coal units and small gas units. Proposed standards are in effect until a final rule is published or another rule is re-proposed. In June 2014, the EPA proposed a rule that would require states to develop CO2 standards that would apply to existing fossil-fueled generating facilities. Specifically, the EPA proposed state-specific rate-based goals for CO2 emissions, as well as guidelines for states to follow in developing plans to achieve the state-specific goals. The EPA anticipates finalizing both of these rules in the summer of 2015.
	Water
	In August 2014, the EPA finalized the regulation regarding the use of water for once through cooling at existing facilities to address impingement and entrainment concerns. NRG anticipates that more stringent requirements will be incorporated into some of its water discharge permits over the next several years.
	Byproducts, Wastes, Hazardous Materials and Contamination
	In April 2015, the EPA finalized the rule regulating byproducts of coal combustion (e.g., ash and gypsum) as solid wastes under the RCRA. In 2010, the EPA had proposed two alternatives. Under the first proposal, these byproducts would be regulated as solid wastes. Under the second proposal, these byproducts would have been regulated as “special wastes” in a manner similar to the regulation of hazardous waste with an exception for certain types of beneficial use of these byproducts. The second alternative would have imposed significantly more stringent requirements and materially increased the cost of disposal of coal combustion byproducts. The Company is evaluating the impact of the new rule on its results of operations, financial condition and cash flows.
	East Region
	Maryland Environmental Regulations — In December 2014, MDE proposed in the Maryland Register a regulation regarding NOx emissions from coal-fired electric generating units, which if finalized would have required by 2020 the Company (at each of the three Dickerson coal-fired units and the Chalk Point coal-fired unit that does not have an SCR) to (1) install and operate an SCR; (2) retire the unit; or (3) convert the fuel source from coal to natural gas. Earlier this year, a new administration decided not to finalize the regulation as proposed. Later this year, the Company expects MDE to propose revised regulations to address future NOx reductions, which when finalized may negatively affect certain of the Company’s coal-fired units in Maryland.
	Environmental Capital Expenditures
	Based on current (and in some cases proposed) rules, technology and preliminary plans based on some proposed rules, NRG estimates that environmental capital expenditures from 2015 through 2019 required to comply with environmental laws will be approximately $614 million which includes $57 million for GenOn and $440 million for Midwest Generation. 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; (iii) NOx controls for Sayreville and Gilbert; and (iv) DSI/ESP upgrades at Waukegan and Powerton to satisfy the IL CPS and the Joliet gas conversion.

Condensed_Consolidating_Financ

Condensed Consolidating Financial Information	3 Months Ended
	Mar. 31, 2015
Condensed Consolidating Financial Information Disclosure [Abstract]
Condensed Consolidating Financial Information	Condensed Consolidating Financial Information
	As of March 31, 2015, the Company had outstanding $6.4 billion of Senior Notes due from 2018 - 2024, 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 and NRG Yield, Inc. and its subsidiaries.
	Unless otherwise noted below, each of the following guarantor subsidiaries fully and unconditionally guaranteed the Senior Notes as of March 31, 2015:
	Ace Energy, Inc.	NEO Freehold-Gen LLC	NRG Operating Services, Inc.
	Allied Warranty LLC	NEO Power Services Inc.	NRG Oswego Harbor Power Operations Inc.
	Arthur Kill Power LLC	New Genco GP, LLC	NRG PacGen Inc.
	Astoria Gas Turbine Power LLC	Norwalk Power LLC	NRG Portable Power LLC
	Bayou Cove Peaking Power, LLC	NRG Affiliate Services Inc.	NRG Power Marketing LLC
	BidURenergy, Inc.	NRG Artesian Energy LLC	NRG Reliability Solutions LLC
	Cabrillo Power I LLC	NRG Arthur Kill Operations Inc.	NRG Renter's Protection LLC
	Cabrillo Power II LLC	NRG Astoria Gas Turbine Operations Inc.	NRG Retail LLC
	Carbon Management Solutions LLC	NRG Bayou Cove LLC	NRG Retail Northeast LLC
	Cirro Group, Inc.	NRG Business Solutions LLC	NRG Rockford Acquisition LLC
	Cirro Energy Services, Inc.	NRG Cabrillo Power Operations Inc.	NRG Saguaro Operations Inc.
	Clean Edge Energy LLC	NRG California Peaker Operations LLC	NRG Security LLC
	Conemaugh Power LLC	NRG Cedar Bayou Development Company, LLC	NRG Services Corporation
	Connecticut Jet Power LLC	NRG Connected Home LLC	NRG SimplySmart Solutions LLC
	Cottonwood Development LLC	NRG Connecticut Affiliate Services Inc.	NRG South Central Affiliate Services Inc.
	Cottonwood Energy Company LP	NRG Construction LLC	NRG South Central Generating LLC
	Cottonwood Generating Partners I LLC	NRG Curtailment Solutions LLC	NRG South Central Operations Inc.
	Cottonwood Generating Partners II LLC	NRG Development Company Inc.	NRG South Texas LP
	Cottonwood Generating Partners III LLC	NRG Devon Operations Inc.	NRG Texas C&I Supply LLC
	Cottonwood Technology Partners LP	NRG Dispatch Services LLC	NRG Texas Gregory LLC
	Devon Power LLC	NRG Distributed Generation PR LLC	NRG Texas Holding Inc.
	Dunkirk Power LLC	NRG Dunkirk Operations Inc.	NRG Texas LLC
	Eastern Sierra Energy Company LLC	NRG El Segundo Operations Inc.	NRG Texas Power LLC
	El Segundo Power, LLC	NRG Energy Efficiency-L LLC	NRG Warranty Services LLC
	El Segundo Power II LLC	NRG Energy Efficiency-P LLC	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 International Inc.	ONSITE Energy, Inc.
	Energy Plus Natural Gas LLC	NRG Energy Services LLC	Oswego Harbor Power LLC
	Energy Protection Insurance Company	NRG Generation Holdings, Inc.	RE Retail Receivables, LLC
	Everything Energy LLC	NRG Home & Business Solutions LLC	Reliant Energy Northeast LLC
	Forward Home Security LLC	NRG Home Services LLC	Reliant Energy Power Supply, LLC
	GCP Funding Company, LLC	NRG Home Solutions LLC	Reliant Energy Retail Holdings, LLC
	Green Mountain Energy	NRG Home Solutions Product LLC	Reliant Energy Retail Services, LLC
	Green Mountain Energy Co LLC	NRG Homer City Services LLC	RERH Holdings LLC
	Gregory Partners, LLC	NRG Huntley Operations Inc.	Saguaro Power LLC
	Gregory Power Partners LLC	NRG HQ DC LLC	Somerset Operations Inc.
	Huntley Power LLC	NRG Identity Protect LLC	Somerset Power LLC
	Independence Energy Alliance LLC	NRG Ilion Limited Partnership	Texas Genco Financing Corp.
	Independence Energy Group LLC	NRG Ilion LP LLC	Texas Genco GP, LLC
	Independence Energy Natural Gas LLC	NRG International LLC	Texas Genco Holdings, Inc.
	Indian River Operations Inc.	NRG Maintenance Services LLC	Texas Genco LP, LLC
	Indian River Power LLC	NRG Mextrans Inc.	Texas Genco Operating Services, LLC
	Keystone Power LLC	NRG MidAtlantic Affiliate Services Inc.	Texas Genco Services, LP
	Langford Wind Power, LLC	NRG Middletown Operations Inc.	US Retailers LLC
	Louisiana Generating LLC	NRG Montville Operations Inc.	Vienna Operations Inc.
	Meriden Gas Turbines LLC	NRG New Roads Holdings LLC	Vienna Power LLC
	Middletown Power LLC	NRG North Central Operations Inc.	WCP (Generation) Holdings LLC
	Montville Power LLC	NRG Northeast Affiliate Services Inc.	West Coast Power LLC
	NEO Corporation	NRG Norwalk Harbor Operations Inc.
	NRG conducts much of its business through and derives much of its income from its subsidiaries. Therefore, the Company's ability to make required payments with respect to its indebtedness and other obligations depends on the financial results and condition of its subsidiaries and NRG's ability to receive funds from its subsidiaries. There are no restrictions on the ability of any of the guarantor subsidiaries to transfer funds to NRG. However, there may be restrictions for certain non-guarantor subsidiaries.
	The following condensed consolidating financial information presents the financial information of NRG Energy, Inc., the guarantor subsidiaries and the non-guarantor subsidiaries in accordance with Rule 3-10 under the SEC Regulation S-X. The financial information may not necessarily be indicative of results of operations or financial position had the guarantor subsidiaries or non-guarantor subsidiaries operated as independent entities.
	In this presentation, NRG Energy, Inc. consists of parent company operations. Guarantor subsidiaries and non-guarantor subsidiaries of NRG are reported on an equity basis. For companies acquired, the fair values of the assets and liabilities acquired have been presented on a push-down accounting basis.
	NRG ENERGY, INC. AND SUBSIDIARIES
	CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS
	For the Three Months Ended March 31, 2015
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Operating Revenues
Total operating revenues	$	2,563		$	1,303		$	—		$	(40	)	$	3,826
Operating Costs and Expenses
Cost of operations	2,104			995			12			(49		)	3,062
Depreciation and amortization	204			186			5			—			395
Selling, general and administrative	102			101			60			—			263
Acquisition-related transaction and integration costs	—			2			8			—			10
Development activity expenses	—			15			19			—			34
Total operating costs and expenses	2,410			1,299			104			(49		)	3,764
Gain on postretirement benefits curtailment	—			14			—			—			14
Operating Income/(Loss)	153			18			(104		)	9			76
Other Income/(Expense)
Equity in earnings of consolidated subsidiaries	(13		)	(8		)	50			(29		)	—
Equity in earnings of unconsolidated affiliates	—			(4		)	(1		)	2			(3		)
Other income, net	1			17			1			—			19
Loss on debt extinguishment	—			—			—			—			—
Interest expense	(4		)	(158		)	(139		)	—			(301		)
Total other expense	(16		)	(153		)	(89		)	(27		)	(285		)
Income/(Loss) Before Income Taxes	137			(135		)	(193		)	(18		)	(209		)
Income tax expense/(benefit)	54			(60		)	(67		)	—			(73		)
Net Income/(Loss)	83			(75		)	(126		)	(18		)	(136		)
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	—			(21		)	(6		)	11			(16		)
Net Income/(Loss) Attributable to	$	83		$	(54	)	$	(120	)	$	(29	)	$	(120	)
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 March 31, 2015
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Net Income/(Loss)	$	83		$	(75	)	$	(126	)	$	(18	)	$	(136	)
Other Comprehensive Income/(Loss), net of tax
Unrealized (loss)/gain on derivatives, net	(7		)	11			(16		)	—			(12		)
Foreign currency translation adjustments, net	—			(9		)	(2		)	—			(11		)
Available-for-sale securities, net	—			(1		)	—			—			(1		)
Defined benefit plan, net	(3		)	(1		)	11			—			7
Other comprehensive (loss)/income	(10		)	—			(7		)	—			(17		)
Comprehensive Income/(Loss)	73			(75		)	(133		)	(18		)	(153		)
Less: Comprehensive income/(loss) attributable to noncontrolling interest and redeemable noncontrolling interest	—			(34		)	(6		)	11			(29		)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	73			(41		)	(127		)	(29		)	(124		)
Dividends for preferred shares	—			—			5			—			5
Comprehensive Income/(Loss) Available for Common Stockholders	$	73		$	(41	)	$	(132	)	$	(29	)	$	(129	)
(a)	All significant intercompany transactions have been eliminated in consolidation.
NRG ENERGY, INC. AND SUBSIDIARIES
CONDENSED CONSOLIDATING BALANCE SHEETS
March 31, 2015
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
ASSETS	(In millions)
Current Assets
Cash and cash equivalents	$	13		$	1,378		$	773		$	—		$	2,164
Funds deposited by counterparties	39			29			—			—			68
Restricted cash	14			427			2			—			443
Accounts receivable, net	936			240			3			—			1,179
Inventory	505			604			—			—			1,109
Derivative instruments	1,480			938			—			(389		)	2,029
Cash collateral paid in support of energy risk management activities	246			154			—			—			400
Accounts receivable - affiliate	8,656			2,103			(5,750		)	(5,002		)	7
Deferred income taxes	—			93			95			—			188
Renewable energy grant receivable	—			68			—			—			68
Prepayments and other current assets	148			319			—			—			467
Total current assets	12,037			6,353			(4,877		)	(5,391		)	8,122
Net property, plant and equipment	8,260			13,847			194			(25		)	22,276
Other Assets
Investment in subsidiaries	422			2,542			21,907			(24,871		)	—
Equity investments in affiliates	(18		)	841			39			(90		)	772
Notes receivable, less current portion	—			58			221			(212		)	67
Goodwill	2,072			448			—			—			2,520
Intangible assets, net	859			1,637			1			(6		)	2,491
Nuclear decommissioning trust fund	586			—			—			—			586
Derivative instruments	318			321			1			(49		)	591
Deferred income tax	(61		)	652			893			—			1,484
Non-current assets held-for-sale	—			17			—			—			17
Other non-current assets	112			681			611			—			1,404
Total other assets	4,290			7,197			23,673			(25,228		)	9,932
Total Assets	$	24,587		$	27,397		$	18,990		$	(30,644	)	$	40,330
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities
Current portion of long-term debt and capital leases	$	1		$	445		$	231		$	(212	)	$	465
Accounts payable	645			358			42			—			1,045
Accounts payable — affiliate	2,336			2,853			(576		)	(4,613		)	—
Derivative instruments	1,439			834			—			(389		)	1,884
Cash collateral received in support of energy risk management activities	39			29			—			—			68
Accrued expenses and other current liabilities	233			496			318			—			1,047
Total current liabilities	4,693			5,015			15			(5,214		)	4,509
Other Liabilities
Long-term debt and capital leases	308			11,456			8,286			—			20,050
Nuclear decommissioning reserve	314			—			—			—			314
Nuclear decommissioning trust liability	328			—			—			—			328
Deferred income taxes	1,284			(1,039		)	(225		)	—			20
Derivative instruments	369			330			—			(49		)	650
Out-of-market contracts	107			1,114			—			—			1,221
Other non-current liabilities	490			767			292			—			1,549
Total non-current liabilities	3,200			12,628			8,353			(49		)	24,132
Total liabilities	7,893			17,643			8,368			(5,263		)	28,641
2.822% convertible perpetual preferred stock	—			—			293			—			293
Redeemable noncontrolling interest in subsidiaries	—			19			—			—			19
Stockholders’ Equity	16,694			9,735			10,329			(25,381		)	11,377
Total Liabilities and Stockholders’ Equity	$	24,587		$	27,397		$	18,990		$	(30,644	)	$	40,330
(a)	All significant intercompany transactions have been eliminated in consolidation.
NRG ENERGY, INC. AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
For the Three Months Ended March 31, 2015
(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	$	820		$	(430	)	$	(539	)	$	409		$	260
Cash Flows from Investing Activities
(Payments for)/proceeds from intercompany loans to subsidiaries	(737		)	328			409			—			—
Acquisition of businesses, net of cash acquired	—			(1		)	—			—			(1		)
Capital expenditures	(89		)	(157		)	(6		)	—			(252		)
Increase in restricted cash, net	—			(11		)	—			—			(11		)
Decrease/(increase) in restricted cash — U.S. DOE projects	—			24			1			—			25
Decrease in notes receivable	—			5			—			—			5
Investments in nuclear decommissioning trust fund securities	(193		)	—			—			—			(193		)
Proceeds from sales of nuclear decommissioning trust fund securities	196			—			—			—			196
Proceeds from renewable energy grants	—			2			—			—			2
Other	(2		)	(2		)	(37		)	—			(41		)
Net Cash Used by Investing Activities	(825		)	188			367			—			(270		)
Cash Flows from Financing Activities
Proceeds/(payments) from intercompany loans	—			—			409			(409		)	—
Payment of dividends to common and preferred stockholders	—			—			(51		)	—			(51		)
Payment for treasury stock	—			—			(79		)	—			(79		)
Net payments for settlement of acquired derivatives that include financing elements	—			40			—			—			40
Proceeds from issuance of long-term debt	—			221			27			—			248
Contributions to, net of distributions from, noncontrolling interest in subsidiaries	—			(25		)	—			—			(25		)
Proceeds from issuance of common stock	—			—			1			—			1
Payments for short and long-term debt	—			(89		)	(5		)	—			(94		)
Net Cash Provided by Financing Activities	—			147			302			(409		)	40
Effect of exchange rate changes on cash and cash equivalents	—			18			—			—			18
Net (Decrease)/Increase in Cash and Cash Equivalents	(5		)	(77		)	130			—			48
Cash and Cash Equivalents at Beginning of Period	18			1,455			643			—			2,116
Cash and Cash Equivalents at End of Period	$	13		$	1,378		$	773		$	—		$	2,164
(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 March 31, 2014
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Operating Revenues
Total operating revenues	$	2,279		$	1,251		$	—		$	(44	)	$	3,486
Operating Costs and Expenses
Cost of operations	1,797			974			(4		)	(30		)	2,737
Depreciation and amortization	198			134			3			—			335
Selling, general and administrative	101			57			64			—			222
Acquisition-related transaction and integration costs	—			1			11			—			12
Development activity expenses	—			10			9			—			19
Total operating costs and expenses	2,096			1,176			83			(30		)	3,325
Gain on sale of assets	—			19			—			—			19
Operating Income/(Loss)	183			94			(83		)	(14		)	180
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	49			(6		)	115			(158		)	—
Equity in earnings of unconsolidated affiliates	4			1			—			2			7
Other income, net	1			4			7			(1		)	11
Loss on debt extinguishment	—			(9		)	(32		)	—			(41		)
Interest expense	(6		)	(107		)	(143		)	1			(255		)
Total other income/(expense)	48			(117		)	(53		)	(156		)	(278		)
Income/(Loss) Before Income Taxes	231			(23		)	(136		)	(170		)	(98		)
Income tax expense/(benefit)	63			(10		)	(84		)	—			(31		)
Net Loss	168			(13		)	(52		)	(170		)	(67		)
Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	—			(3		)	4			(12		)	(11		)
Net Income/(Loss) Attributable to NRG Energy, Inc.	$	168		$	(10	)	$	(56	)	$	(158	)	$	(56	)
(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 March 31, 2014
(Unaudited)
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
	(In millions)
Net Income/(Loss)	$	168		$	(13	)	$	(52	)	$	(170	)	$	(67	)
Other Comprehensive (Loss)/Income, net of tax
Unrealized gain/(loss) on derivatives, net	6			(6		)	5			(14		)	(9		)
Foreign currency translation adjustments, net	—			6			—			—			6
Available-for-sale securities, net	—			—			4			2			6
Defined benefit plan	2			—			—			—			2
Other comprehensive income/(loss)	8			—			9			(12		)	5
Comprehensive Income/(Loss)	176			(13		)	(43		)	(182		)	(62		)
Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	—			(5		)	4			(14		)	(15		)
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	176			(8		)	(47		)	(168		)	(47		)
Dividends for preferred shares	—			—			2			—			2
Comprehensive Income/(Loss) Available for Common Stockholders	$	176		$	(8	)	$	(49	)	$	(168	)	$	(49	)
(a)	All significant intercompany transactions have been eliminated in consolidation.
NRG ENERGY, INC. AND SUBSIDIARIES
CONDENSED CONSOLIDATING BALANCE SHEETS
December 31, 2014
	Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
							(Note Issuer)
ASSETS	(In millions)
Current Assets
Cash and cash equivalents	$	18		$	1,455		$	643		$	—		$	2,116
Funds deposited by counterparties	9			63			—			—			72
Restricted cash	5			451			1			—			457
Accounts receivable, net	924			392			6			—			1,322
Inventory	537			710			—			—			1,247
Derivative instruments	1,657			1,209			—			(441		)	2,425
Accounts receivable - affiliate	7,449			1,988			(5,991		)	(3,437		)	9
Cash collateral paid in support of energy risk management activities	114			73			—			—			187
Renewable energy grant receivable	—			134			1			—			135
Prepayments and other current assets	94			175			343			—			612
Total current assets	10,807			6,650			(4,997		)	(3,878		)	8,582
Net Property, Plant and Equipment	8,344			13,877			171			(25		)	22,367
Other Assets
Investment in subsidiaries	140			2,293			23,410			(25,843		)	—
Equity investments in affiliates	(18		)	891			—			(102		)	771
Capital leases and notes receivable, less current portion	1			60			109			(98		)	72
Goodwill	1,921			653			—			—			2,574
Intangible assets, net	765			1,806			2			(6		)	2,567
Nuclear decommissioning trust fund	585			—			—			—			585
Deferred income taxes	(247		)	816			837			—			1,406
Derivative instruments	242			288			1			(51		)	480
Non-current assets held for sale	—			17			—			—			17
Other non-current assets	113			623			508			—			1,244
Total other assets	3,502			7,447			24,867			(26,100		)	9,716
Total Assets	$	22,653		$	27,974		$	20,041		$	(30,003	)	$	40,665
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities
Current portion of long-term debt and capital leases	$	1		$	444		$	127		$	(98	)	$	474
Accounts payable	598			416			46			—			1,060
Accounts payable — affiliate	1,588			2,447			(598		)	(3,437		)	—
Deferred Income Taxes	7			—			(7		)	—			—
Derivative instruments	1,532			963			—			(441		)	2,054
Cash collateral received in support of energy risk management activities	9			63			—			—			72
Accrued expenses and other current liabilities	283			498			418			—			1,199
Total current liabilities	4,018			4,831			(14		)	(3,976		)	4,859
Other Liabilities
Long-term debt and capital leases	307			11,226			8,367			—			19,900
Nuclear decommissioning reserve	310			—			—			—			310
Nuclear decommissioning trust liability	333			—			—			—			333
Deferred income taxes	1,036			(1,012		)	(3		)	—			21
Derivative instruments	248			241			—			(51		)	438
Out-of-market contracts	111			1,133			—			—			1,244
Other non-current liabilities	465			795			314			—			1,574
Total non-current liabilities	2,810			12,383			8,678			(51		)	23,820
Total Liabilities	6,828			17,214			8,664			(4,027		)	28,679
2.822% Preferred Stock	—			—			291			—			291
Redeemable noncontrolling interest in subsidiaries	—			19			—			—			19
Stockholders’ Equity	15,825			10,741			11,086			(25,976		)	11,676
Total Liabilities and Stockholders’ Equity	$	22,653		$	27,974		$	20,041		$	(30,003	)	$	40,665
(a)	All significant intercompany transactions have been eliminated in consolidation.
NRG ENERGY, INC. AND SUBSIDIARIES
CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
For the Three Months Ended March 31, 2014
(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 by Operating Activities	$	446		$	430		$	(886	)	$	401		$	391
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	(405		)	4			401			—			—
Acquisition of businesses, net of cash acquired	—			(25		)	(193		)	—			(218		)
Capital expenditures	(73		)	(162		)	(2		)	—			(237		)
(Increase)/decrease in restricted cash, net	—			3			—			—			3
Increase in restricted cash — U.S. DOE projects	(4		)	60			—			—			56
Decrease/(increase) in notes receivable	—			1			—			—			1
Investments in nuclear decommissioning trust fund securities	(188		)	—			—			—			(188		)
Proceeds from sales of nuclear decommissioning trust fund securities	183			—			—			—			183
Proceeds from renewable energy grants	—			387			—			—			387
Proceeds from sale of assets	—			—			77			—			77
Cash proceeds to fund cash grant bridge loan payment	—			57			—			—			57
Other	7			(4		)	—			—			3
Net Cash (Used)/Provided by Investing Activities	(480		)	321			283			—			124
Cash Flows from Financing Activities
Proceeds from intercompany loans	—			—			401			(401		)	—
Payment of dividends to preferred stockholders	—			—			(41		)	—			(41		)
Net (payment for)/receipts from settlement of acquired derivatives that include financing elements	—			(223		)	—			—			(223		)
Proceeds from issuance of long-term debt	—			464			1,100			—			1,564
Proceeds from issuance of common stock	—			—			3			—			3
Sale proceeds and other contributions from noncontrolling interest in subsidiaries	—			9			—			—			9
Payment of debt issuance costs	—			(9		)	(14		)	—			(23		)
Payments for short and long-term debt	—			(405		)	(468		)	—			(873		)
Net Cash (Used)/Provided by Financing Activities	—			(164		)	981			(401		)	416
Effect of exchange rate changes on cash and cash equivalents	—			2			—			—			2
Net (Decrease)/Increase in Cash and Cash Equivalents	(34		)	589			378			—			933
Cash and Cash Equivalents at Beginning of Period	56			870			1,328			—			2,254
Cash and Cash Equivalents at End of Period	$	22		$	1,459		$	1,706		$	—		$	3,187
(a)	All significant intercompany transactions have been eliminated in consolidation.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Business Description and Basis of Presentation [Text Block]	The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with the SEC's regulations for interim financial information and with the instructions to Form 10-Q. Accordingly, they do not include all of the information and notes required by generally accepted accounting principles for complete financial statements. The following notes should be read in conjunction with the accounting policies and other disclosures as set forth in the notes to the consolidated financial statements in the Company's 2014 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 March 31, 2015, and the results of operations, comprehensive income/(loss) and cash flows for the three months ended March 31, 2015, and 2014.
Reclassification, Policy [Policy Text Block]	Reclassifications
	Certain prior year amounts have been reclassified for comparative purposes. The reclassifications did not affect results from operations or cash flows.
Use of Estimates (Policy)	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the U.S. 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.
Cash Flow, Supplemental Disclosures [Text Block]	Other Cash Flow Information
	NRG’s investing activities exclude capital expenditures of $40 million which were accrued and unpaid at March 31, 2015
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Developments
	ASU 2015-03 — In April 2015, the FASB issued ASU No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs, or ASU No. 2015-03. The amendments of ASU No. 2015-03 were issued to reduce complexity in the balance sheet presentation of debt issuance costs. ASU No. 2015-03 requires that debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of debt liability, consistent with debt discounts or premiums. The recognition and measurement guidance for debt issuance costs are not affected by the amendments in this standard. The guidance in ASU No. 2015-03 is effective for financial statements issued for fiscal years beginning after December 15, 2015, and interim periods within those fiscal years. Early adoption is permitted for financial statements that have not been previously issued. The adoption of this standard is not expected to have a material impact on the Company's balance sheets on a gross basis and will have no impact on net assets.
	ASU 2015-02 — In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis, or ASU No. 2015-02. The amendments of ASU No. 2015-02 were issued in an effort to minimize situations under previously existing guidance in which a reporting entity was required to consolidate another legal entity in which that reporting entity did not have: (1) the ability through contractual rights to act primarily on its own behalf; (2) ownership of the majority of the legal entity's voting rights; or (3) the exposure to a majority of the legal entity's economic benefits. ASU No. 2015-02 affects reporting entities that are required to evaluate whether they should consolidate certain legal entities. All legal entities are subject to reevaluation under the revised consolidation model. The guidance in ASU No. 2015-02 is effective for periods beginning after December 15, 2015. Early adoption is permitted. The Company adopted the standard effective January 1, 2015 and the adoption of this standard did not impact the Company's results of operations, cash flows or financial position.
	ASU 2014-16 — In November 2014, the FASB issued ASU No. 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share Is More Akin to Debt or to Equity, or ASU No. 2014-16. The amendments of ASU No. 2014-16 clarify how U.S. GAAP should be applied in determining whether the nature of a host contract is more akin to debt or equity and in evaluating whether the economic characteristics and risks of an embedded feature are "clearly and closely related" to its host contract. The guidance in ASU No. 2014-16 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. The Company adopted the standard effective January 1, 2015 and the adoption of this standard did not impact the Company's results of operations, cash flows or financial position.
	ASU 2014-09 — In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), or ASU No. 2014-09. The amendments of ASU No. 2014-09 complete the joint effort between the FASB and the International Accounting Standards Board, or IASB, to develop a common revenue standard for U.S. GAAP and International Financial Reporting Standards, or IFRS, and to improve financial reporting. The guidance in ASU No. 2014-09 provides that an entity should recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for the goods or services provided and establishes the following steps to be applied by an entity: (1) identify the contract with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies the performance obligation. The guidance of ASU No. 2014-09 is effective for annual reporting periods beginning after December 15, 2016, including interim periods therein. Early adoption is not permitted. The Company is currently evaluating the impact of the standard on the Company's results of operations, cash flows and financial position.
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 in December 2014, 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 segregated as follows: NRG Business, which includes conventional power generation, the carbon capture business and energy services; NRG Home, which includes NRG Home Retail, consisting of residential retail services and products, and NRG Home Solar, which includes the installation and leasing of residential solar systems and the sale of solar energy services; NRG Renew, which includes solar and wind assets, excluding those in the NRG Yield segment; NRG Yield; and corporate activities.  NRG Yield includes certain of the Company's contracted generation assets. On January 2, 2015, NRG Yield, Inc. acquired three projects from the Company: Walnut Creek formerly in the NRG Business segment, the Tapestry projects (Buffalo Bear, Pinnacle and Taloga) and Laredo Ridge, both formerly in the NRG Renew segment. As the transaction was accounted for as a transfer of entities under common control, all historical periods have been recast to reflect this change. The Company's corporate segment includes international business and electric vehicle services. Intersegment sales are accounted for at market.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Schedule of Change in Noncontrolling Interest	Noncontrolling Interest
	The following table reflects the changes in NRG's noncontrolling interest balance:
		(In millions)
	Balance as of December 31, 2014	$	1,914
	Sale of assets to NRG Yield, Inc.	(27		)
	Distributions to noncontrolling interest	(24		)
	Non-cash increase to noncontrolling interest	14
	Comprehensive loss attributable to noncontrolling interest	(29		)
	Balance as of March 31, 2015	$	1,848

Business_Acquisitions_and_Disp1

Business Acquisitions and Dispositions (Tables)	3 Months Ended
	Mar. 31, 2015
EME [Member]
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The purchase price of $3.5 billion was allocated as follows:
		Acquisition Date Fair Value at December 31, 2014		Measurement period adjustments			Revised Acquisition Date
		(In millions)
	Assets
	Cash	$	1,422	$	—		$	1,422
	Current assets	724		72			796
	Property, plant and equipment	2,438		(3		)	2,435
	Intangible assets	172		—			172
	Goodwill	334		(56		)	278
	Non-current assets	773		—			773
	Total assets acquired	5,863		13			5,876
	Liabilities
	Current and non-current liabilities	629		13			642
	Out-of-market contracts and leases	159		—			159
	Long-term debt	1,249		—			1,249
	Total liabilities assumed	2,037		13			2,050
	Less: noncontrolling interest	352		—			352
	Net assets acquired	$	3,474	$	—		$	3,474
Alta Wind Holdings [Member]
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following table summarizes the provisional amounts recognized for assets acquired and liabilities assumed as of December 31, 2014, as well as adjustments made through March 31, 2015. The purchase price of $923 million was provisionally allocated as follows:
		Acquisition Date Fair Value at December 31, 2014		Measurement period adjustments			Revised Acquisition Date
		(In millions)
	Assets
	Cash	$	22	$	—		$	22
	Current and non-current assets	49		(2		)	47
	Property, plant and equipment	1,304		6			1,310
	Intangible assets	1,177		(6		)	1,171
	Total assets acquired	2,552		(2		)	2,550
	Liabilities
	Debt	1,591		—			1,591
	Current and non-current liabilities	38		(2		)	36
	Total liabilities assumed	1,629		(2		)	1,627
	Net assets acquired	$	923	$	—		$	923

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
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 March 31, 2015				As of December 31, 2014
		Carrying Amount		Fair Value		Carrying Amount		Fair Value
		(In millions)
	Assets:
	Notes receivable (a)	$	86	$	86	$	91	$	91
	Liabilities:
	Long-term debt, including current portion	$	20,509	$	20,679	$	20,366	$	20,361
	(a) Includes the current portion of notes receivable which is recorded in prepayments and other current assets on the Company's consolidated balance sheets.
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 March 31, 2015
		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	$	—	$	—	$	18	$	18
	Available-for-sale securities	24		—		—		24
	Other (a)	20		—		11		31
	Nuclear trust fund investments:
	Cash and cash equivalents	5		—		—		5
	U.S. government and federal agency obligations	50		3		—		53
	Federal agency mortgage-backed securities	—		71		—		71
	Commercial mortgage-backed securities	—		24		—		24
	Corporate debt securities	—		84		—		84
	Equity securities	293		—		54		347
	Foreign government fixed income securities	—		2		—		2
	Other trust fund investments:
	U.S. government and federal agency obligations	1		—		—		1
	Derivative assets:
	Commodity contracts	998		1,358		264		2,620
	Total assets	$	1,391	$	1,542	$	347	$	3,280
	Derivative liabilities:
	Commodity contracts	$	964	$	1,142	$	230	$	2,336
	Interest rate contracts	—		198		—		198
	Total liabilities	$	964	$	1,340	$	230	$	2,534
	(a) Consists primarily of mutual funds held in a Rabbi Trust for non-qualified deferred compensation plans for certain former employees and a total return swap that does not meet the definition of a derivative.
		As of December 31, 2014
		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	$	—	$	—	$	18	$	18
	Available-for-sale securities	30		—		—		30
	Other (a)	21		—		11		32
	Nuclear trust fund investments:
	Cash and cash equivalents	14		—		—		14
	U.S. government and federal agency obligations	44		3		—		47
	Federal agency mortgage-backed securities	—		74		—		74
	Commercial mortgage-backed securities	—		25		—		25
	Corporate debt securities	—		78		—		78
	Equity securities	292		—		52		344
	Foreign government fixed income securities	—		3		—		3
	Other trust fund investments:
	U.S. government and federal agency obligations	1		—		—		1
	Derivative assets:
	Commodity contracts	1,078		1,515		309		2,902
	Interest rate contracts	—		2		—		2
	Equity contracts	—		—		1		1
	Total assets	$	1,480	$	1,700	$	391	$	3,571
	Derivative liabilities:
	Commodity contracts	$	1,004	$	1,093	$	230	$	2,327
	Interest rate contracts	—		165		—		165
	Total liabilities	$	1,004	$	1,258	$	230	$	2,492
	(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 months ended March 31, 2015, and 2014, 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 March 31, 2015
	(In millions)	Debt Securities		Other		Trust Fund Investments		Derivatives(a)			Total
	Beginning balance	$	18	$	11	$	52	$	80		$	161
	Total gains/(losses) — realized/unrealized:
	Included in earnings	—		—		—		(55		)	(55		)
	Included in nuclear decommissioning obligation	—		—		2		—			2
	Purchases	—		—		—		(4		)	(4		)
	Transfers into Level 3 (b)	—		—		—		15			15
	Transfers out of Level 3 (b)	—		—		—		(2		)	(2		)
	Ending balance as of March 31, 2015	$	18	$	11	$	54	$	34		$	117
	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 March 31, 2015	$	—	$	—	$	—	(20		)	$	(20	)
	(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 March 31, 2014
	(In millions)	Debt Securities		Other		Trust Fund Investments		Derivatives(a)			Total
	Beginning balance	$	16	$	10	$	56	$	13		$	95
	Total gains/(losses) — realized/unrealized:
	Included in earnings	—		1		—		16			17
	Included in OCI	2		—		—		—			2
	Purchases	—		—		—		(21		)	(21		)
	Contracts acquired in Dominion acquisition	—		—		—		3			3
	Transfers into Level 3 (b)	—		—		—		18			18
	Transfers out of Level 3 (b)	—		—		—		(6		)	(6		)
	Ending balance as of March 31, 2014	$	18	$	11	$	56	$	23		$	108
	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 March 31, 2014	—		—		—		19			19
	(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	48	%
	Utilities, energy merchants, marketers and other	32
	ISOs	20
	Total as of March 31, 2015	100	%
		Net Exposure (a)
	Category	(% of Total)
	Investment grade	96	%
	Non-rated (b)	2
	Non-investment grade	2
	Total as of March 31, 2015	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)	3 Months Ended
	Mar. 31, 2015
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 March 31, 2015							As of December 31, 2014
	(In millions, except otherwise noted)	Fair Value		Unrealized Gains		Unrealized Losses		Weighted-average Maturities (In years)	Fair Value		Unrealized Gains		Unrealized Losses		Weighted-average Maturities (In years)
	Cash and cash equivalents	$	5	$	—	$	—	—	$	14	$	—	$	—	—
	U.S. government and federal agency obligations	53		3		—		10	47		2		—		11
	Federal agency mortgage-backed securities	71		2		—		24	74		2		—		25
	Commercial mortgage-backed securities	24		—		1		30	25		—		1		30
	Corporate debt securities	84		2		—		10	78		2		1		11
	Equity securities	347		211		—		—	344		211		—		—
	Foreign government fixed income securities	2		—		—		15	3		1		—		16
	Total	$	586	$	218	$	1		$	585	$	218	$	2
Summary of proceeds from sales of available-for-sale securities and the related realized gains and losses	The following table summarizes proceeds from sales of available-for-sale securities and the related realized gains and losses from these sales. The cost of securities sold is determined on the specific identification method.
		Three months ended March 31,
		2015		2014
		(In millions)
	Realized gains	$	6	$	3
	Realized losses	2		1
	Proceeds from sale of securities	196		183

Accounting_for_Derivative_Inst1

Accounting for Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net notional volume buy/(sell) of NRG's open derivative transactions broken out by commodity	The following table summarizes the net notional volume buy/(sell) of NRG's open derivative transactions broken out by category, excluding those derivatives that qualified for the NPNS exception as of March 31, 2015, and December 31, 2014. 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
			March 31, 2015				December 31, 2014
	Category	Units	(In millions)
	Emissions	Short Ton	4				2
	Coal	Short Ton	48				57
	Natural Gas	MMBtu	(35		)		(58		)
	Oil	Barrel	1				1
	Power	MWh	(52		)		(56		)
	Capacity	MW/Day	(1		)		—
	Interest	Dollars	$	3,399			$	3,440
	Equity	Shares	2				2
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
		March 31, 2015				December 31, 2014				March 31, 2015				December 31, 2014
		(In millions)
	Derivatives designated as cash flow hedges:
	Interest rate contracts current	$	—			$	—			$	51			$	55
	Interest rate contracts long-term	—				2				97				74
	Commodity contracts current	—				—				—				—
	Commodity contracts long-term	—				—				—				—
	Total derivatives designated as cash flow hedges	—				2				148				129
	Derivatives not designated as cash flow hedges:
	Interest rate contracts current	—				—				9				8
	Interest rate contracts long-term	—				—				41				28
	Commodity contracts current	2,029				2,425				1,824				1,991
	Commodity contracts long-term	591				477				512				336
	Equity contracts long-term	—				1				—				—
	Total derivatives not designated as cash flow hedges	2,620				2,903				2,386				2,363
	Total derivatives	$	2,620			$	2,905			$	2,534			$	2,492
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 March 31, 2015		(In millions)
	Commodity contracts:
	Derivative assets		$	2,620			$	(2,092	)		$	(64	)		$	464
	Derivative liabilities		(2,336		)		2,092				55				(189		)
	Total commodity contracts		284				—				(9		)		275
	Interest rate contracts:
	Derivative liabilities		(198		)		—				—				(198		)
	Total derivative instruments		$	86			$	—			$	(9	)		$	77
			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, 2014		(In millions)
	Commodity contracts:
	Derivative assets		$	2,902			$	(2,155	)		$	(72	)		$	675
	Derivative liabilities		(2,327		)		2,155				27				(145		)
	Total commodity contracts		575				—				(45		)		530
	Interest rate contracts:
	Derivative assets		2				(2		)		—				—
	Derivative liabilities		(165		)		2				—				(163		)
	Total interest rate contracts		(163		)		—				—				(163		)
	Equity contracts:
	Derivative assets		1				—				—				1
	Total derivative instruments		$	413			$	—			$	(45	)		$	368
Effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax	The following table summarizes the effects of ASC 815 on the Company's accumulated OCI balance attributable to cash flow hedge derivatives, net of tax:
		Three months ended March 31, 2015
		Energy Commodities				Interest Rate				Total
		(In millions)
	Accumulated OCI beginning balance	$	(1	)		$	(67	)		$	(68	)
	Reclassified from accumulated OCI to income:
	Due to realization of previously deferred amounts	—				2				2
	Mark-to-market of cash flow hedge accounting contracts	—				(18		)		(18		)
	Accumulated OCI ending balance, net of $50 tax	$	(1	)		$	(83	)		$	(84	)
	Losses expected to be realized from OCI during the next 12 months, net of $7 tax	$	(1	)		$	(13	)		$	(14	)
		Three months ended March 31, 2014
		Energy Commodities				Interest Rate				Total
		(In millions)
	Accumulated OCI beginning balance	$	(1	)		$	(22	)		$	(23	)
	Reclassified from accumulated OCI to income:
	Due to realization of previously deferred amounts	—				(1		)		(1		)
	Mark-to-market of cash flow hedge accounting contracts	—				(8		)		(8		)
	Accumulated OCI ending balance, net of $17 tax	$	(1	)		$	(31	)		$	(32	)
	Losses expected to be realized from OCI during the next 12 months, net of $7 tax	$	(1	)		$	(13	)		$	(14	)
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 March 31,
		2015				2014
	Unrealized mark-to-market results	(In millions)
	Reversal of previously recognized unrealized (gains)/losses on settled positions related to economic hedges	$	(114	)		$	3
	Reversal of acquired gain positions related to economic hedges	(26		)		(78		)
	Net unrealized losses on open positions related to economic hedges	(138		)		(193		)
	Total unrealized mark-to-market losses for economic hedging activities	(278		)		(268		)
	Reversal of previously recognized unrealized gains on settled positions related to trading activity	(21		)		—
	Reversal of acquired gain positions related to trading activity	(7		)		(1		)
	Net unrealized gains on open positions related to trading activity	6				16
	Total unrealized mark-to-market (losses)/gains for trading activity	(22		)		15
	Total unrealized losses	$	(300	)		$	(253	)
		Three months ended March 31,
		2015				2014
		(In millions)
	Unrealized losses included in operating revenues	$	(109	)		$	(316	)
	Unrealized (losses)/gains included in cost of operations	(191		)		63
	Total impact to statement of operations — energy commodities	$	(300	)		$	(253	)
	Total impact to statement of operations — interest rate contracts	$	(14	)		$	(4	)

Debt_and_Capital_Leases_Debt_a

Debt and Capital Leases Debt and Capital Leases (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Instrument [Line Items]
Long-term debt and capital leases	Long-term debt and capital leases consisted of the following:
	(In millions, except rates)	March 31, 2015		December 31, 2014		Current interest rate % (a)
	Recourse debt:
	Senior notes, due 2018	$	1,130	$	1,130	7.625
	Senior notes, due 2020	1,063		1,063		8.25
	Senior notes, due 2021	1,128		1,128		7.875
	Senior notes, due 2022	1,100		1,100		6.25
	Senior notes, due 2023	990		990		6.625
	Senior notes, due 2024	1,000		1,000		6.25
	Term loan facility, due 2018	1,978		1,983		L+2.00
	Tax-exempt bonds	434		406		4.125 - 6.00
	Subtotal NRG recourse debt	8,823		8,800
	Non-recourse debt:
	GenOn senior notes	2,121		2,133		7.875 - 9.875
	GenOn Americas Generation senior notes	926		929		8.500 - 9.125
	GenOn Other	60		60		various
	Subtotal GenOn debt (non-recourse to NRG)	3,107		3,122
	NRG Yield Operating LLC Senior Notes, due 2024	500		500		5.375
	NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2019	195		—		L+2.25
	NRG Yield, Inc. Convertible Senior Notes, due 2019	327		326		3.5
	NRG West Holdings LLC, due 2023 (El Segundo Energy Center)	484		506		L+2.25 - L+2.875
	NRG Marsh Landing, due 2017 and 2023	457		464		L+1.75 - L+1.875
	Alta Wind I - V lease financing arrangements, due 2034 and 2035	1,036		1,036		5.696-7.015
	Alta Wind X, due 2021	300		300		L+2.00
	Alta Wind XI, due 2021	191		191		L+2.00
	Walnut Creek, term loans due 2023	384		391		L+1.625
	Tapestry Wind LLC, due 2021	188		192		L+1.625
	Laredo Ridge Wind LLC, due 2026	107		108		L+1.875
	NRG Solar Alpine LLC, due 2022	162		163		L+1.750
	NRG Energy Center Minneapolis LLC, due 2017 and 2025	119		121		5.95 - 7.25
	NRG Yield - other	487		489		various
	Subtotal NRG Yield debt (non-recourse to NRG)	4,937		4,787
	Ivanpah Financing, due 2033 and 2038	1,179		1,187		2.285 - 4.256
	Agua Caliente Solar LLC, due 2037	907		898		2.395 - 3.633
	CVSR High Plains Ranch II LLC, due 2037	802		815		2.339 - 3.775
	Viento Funding II, Inc., due 2023	196		196		L+2.75
	NRG Peaker Finance Co. LLC, bonds due 2019	101		100		L+1.07
	Cedro Hill Wind LLC, due 2025	108		111		L+3.125
	NRG - other	349		350		various
	Subtotal NRG non-recourse debt	3,642		3,657
	Subtotal non-recourse debt (including GenOn and NRG Yield)	11,686		11,566
	Subtotal long-term debt (including current maturities)	20,509		20,366
	Capital leases:
	Chalk Point capital lease, due 2015	3		5		8.19
	Other	3		3		various
	Subtotal long-term debt and capital leases (including current maturities)	20,515		20,374
	Less current maturities	465		474
	Total long-term debt and capital leases	$	20,050	$	19,900
	(a) As of March 31, 2015, L+ equals 3 month LIBOR plus x%, with the exception of the Viento Funding II term loan which is 6 month LIBOR plus x% and the NRG West Holdings LLC term loan, NRG Marsh Landing term loan, Walnut Creek term loan, and NRG Yield Operating LLC Revolving Credit facility which are 1 month LIBOR plus x%.

Variable_Interest_Entities_Sum

Variable Interest Entities Summarized Financial Information (Tables)	3 Months Ended
	Mar. 31, 2015
Condensed Financial Statements
Additional Financial Information Disclosure [Text Block]	The summarized financial information for Capistrano Wind Holdings consisted of the following:
	(In millions)	March 31, 2015
	Current assets	$	28
	Net property, plant and equipment	578
	Other long-term assets	137
	Total assets	743
	Current liabilities	36
	Long-term debt	180
	Other long-term liabilities	154
	Total liabilities	370
	Noncontrolling interests	348
	Net assets less noncontrolling interests	$	25

Changes_in_Capital_Structure_T

Changes in Capital Structure (Tables)	3 Months Ended
	Mar. 31, 2015
Changes in Capital Structure Disclosure [Abstract]
Class of Treasury Stock [Table Text Block]	The following table reflects the repurchases made under the 2015 Capital Allocation Program:
			Total number of shares purchased		Average price paid per share (a)				Amounts paid for shares purchased  (in millions) (a)
	2015 Capital Allocation Program
	Dec-14		1,624,360		$	26.95			$	44
	Jan-15		1,755,976		25.19				44
	Feb-15		468,854		25.46				12
	Mar-15		921,654		24.92				23
	Total Repurchases - First Quarter 2015		3,146,484						79
	Apr-15		1,328,329		24.47				33
	Total Repurchases under 2015 Capital Allocation Program		6,099,173		—				$	156
	(a) The average price paid per share and amounts paid for shares purchased excludes the commissions of $0.015 per share paid in connection with the share repurchase.
Changes in NRG's common shares issued and outstanding	The following table reflects the changes in NRG's common stock issued and outstanding:
		Issued		Treasury			Outstanding
	Balance as of December 31, 2014	415,506,176		(78,843,552	)		336,662,624
	Shares issued under LTIPs	1,176,486		—			1,176,486
	Shares issued under ESPP	—		124,625			124,625
	Shares repurchased under Capital Allocation Program	—		(3,146,484	)		(3,146,484	)
	Balance as of March 31, 2015	416,682,662		(81,865,411	)		334,817,251
Schedule of dividends paid	The following table lists the dividends paid during the three months ended March 31, 2015:
		First Quarter 2015
	Dividends per Common Share	$	0.145

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Reconciliation of NRG's basic and diluted earnings per share	The reconciliation of NRG's basic and diluted loss per share is shown in the following table:
		Three months ended March 31,
	(In millions, except per share data)	2015				2014
	Basic and diluted loss per share attributable to NRG Energy, Inc. common stockholders
	Net loss attributable to NRG Energy, Inc.	$	(120	)		$	(56	)
	Dividends for preferred shares	5				2
	Loss available for common stockholders	$	(125	)		$	(58	)
	Weighted average number of common shares outstanding - basic and diluted	336				324
	Loss per weighted average common share — basic and diluted	$	(0.37	)		$	(0.18	)
Summary of NRG's outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company's diluted earnings per share	The following table summarizes NRG’s outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company’s diluted loss per share:
		Three months ended March 31,
	(In millions of shares)	2015			2014
	Equity compensation plans	7			8
	Embedded derivative of 2.822% redeemable perpetual preferred stock(a)	16			16
	Total	23			24
	(a) As of March 31, 2014, the redeemable perpetual preferred stock had an interest rate of 3.625%.

Segment_Reporting_Tables

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting Disclosure [Abstract]
Schedule of segment reporting information, by segment
					NRG Home
	(In millions)	NRG Business(a)			Retail(a)		Solar(a)			NRG Renew(a)			NRG Yield(a)			Corporate(a)			Eliminations			Total
	Three months ended March 31, 2015	(in millions)
	Operating revenues(a)	$	2,506		$	1,311	$	5		$	110		$	180		$	(7	)	$	(279	)	$	3,826
	Depreciation and amortization	233			30		6			65			54			7			—			395
	Equity in (loss)/earnings of unconsolidated affiliates	(4		)	—		—			—			1			(1		)	1			(3		)
	Income/(loss) before income taxes	29			104		(45		)	(61		)	(20		)	(217		)	1			(209		)
	Net income/(loss) attributable to NRG Energy, Inc.	$	29		$	104	$	(45	)	$	(50	)	$	(11	)	$	(142	)	$	(5	)	(120		)
	Total assets as of March 31, 2015	$	28,744		$	6,270	$	178		$	7,155		$	6,595		$	31,493		$	(40,105	)	$	40,330
	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	246		$	—	$	—		$	—		$	—		$	33		$	—		$	279
					NRG Home
	(In millions)	NRG Business(b)			Retail(b)		Solar(b)			NRG Renew(b)(c)			NRG Yield(b)			Corporate(b)(c)			Eliminations			Total
	Three months ended March 31, 2014	(in millions)
	Operating revenues(b)	$	2,346		$	1,082	$	2		$	53		$	140		$	4		$	(141	)	$	3,486
	Depreciation and amortization	225			30		1			49			24			6			—			335
	Equity in earnings/(loss) of unconsolidated affiliates	5			—		—			(3		)	1			2			2			7
	(Loss)/income before income taxes	(6		)	185		(2		)	(65		)	29			(239		)	—			(98		)
	Net (loss)/income attributable to NRG Energy, Inc.	$	(6	)	$	185	$	(2	)	$	(48	)	$	22		$	(209	)	$	2		(56		)
	(b) Operating revenues include inter-segment sales and net derivative gains and losses of:	$	113		$	2	$	—		$	—		$	—		$	26		$	—		$	141
	(c) Includes loss on debt extinguishment of:	$	—		$	—	$	—		$	(1	)	$	—		$	(40	)	$	—		$	(41	)

Income_Taxes_Tables

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The income tax provision consisted of the following:
		Three months ended March 31,
	(In millions except otherwise noted)	2015			2014
	Loss before income taxes	$	(209	)	$	(98	)
	Income tax benefit	(73		)	(31		)
	Effective tax rate	34.9		%	31.6		%

Condensed_Consolidating_Financ1

Condensed Consolidating Financial Information (Tables)	3 Months Ended
	Mar. 31, 2015
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 March 31, 2015
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Operating Revenues
	Total operating revenues	$	2,563		$	1,303		$	—		$	(40	)	$	3,826
	Operating Costs and Expenses
	Cost of operations	2,104			995			12			(49		)	3,062
	Depreciation and amortization	204			186			5			—			395
	Selling, general and administrative	102			101			60			—			263
	Acquisition-related transaction and integration costs	—			2			8			—			10
	Development activity expenses	—			15			19			—			34
	Total operating costs and expenses	2,410			1,299			104			(49		)	3,764
	Gain on postretirement benefits curtailment	—			14			—			—			14
	Operating Income/(Loss)	153			18			(104		)	9			76
	Other Income/(Expense)
	Equity in earnings of consolidated subsidiaries	(13		)	(8		)	50			(29		)	—
	Equity in earnings of unconsolidated affiliates	—			(4		)	(1		)	2			(3		)
	Other income, net	1			17			1			—			19
	Loss on debt extinguishment	—			—			—			—			—
	Interest expense	(4		)	(158		)	(139		)	—			(301		)
	Total other expense	(16		)	(153		)	(89		)	(27		)	(285		)
	Income/(Loss) Before Income Taxes	137			(135		)	(193		)	(18		)	(209		)
	Income tax expense/(benefit)	54			(60		)	(67		)	—			(73		)
	Net Income/(Loss)	83			(75		)	(126		)	(18		)	(136		)
	Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	—			(21		)	(6		)	11			(16		)
	Net Income/(Loss) Attributable to	$	83		$	(54	)	$	(120	)	$	(29	)	$	(120	)
	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 March 31, 2014
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Operating Revenues
	Total operating revenues	$	2,279		$	1,251		$	—		$	(44	)	$	3,486
	Operating Costs and Expenses
	Cost of operations	1,797			974			(4		)	(30		)	2,737
	Depreciation and amortization	198			134			3			—			335
	Selling, general and administrative	101			57			64			—			222
	Acquisition-related transaction and integration costs	—			1			11			—			12
	Development activity expenses	—			10			9			—			19
	Total operating costs and expenses	2,096			1,176			83			(30		)	3,325
	Gain on sale of assets	—			19			—			—			19
	Operating Income/(Loss)	183			94			(83		)	(14		)	180
	Other Income/(Expense)
	Equity in earnings/(losses) of consolidated subsidiaries	49			(6		)	115			(158		)	—
	Equity in earnings of unconsolidated affiliates	4			1			—			2			7
	Other income, net	1			4			7			(1		)	11
	Loss on debt extinguishment	—			(9		)	(32		)	—			(41		)
	Interest expense	(6		)	(107		)	(143		)	1			(255		)
	Total other income/(expense)	48			(117		)	(53		)	(156		)	(278		)
	Income/(Loss) Before Income Taxes	231			(23		)	(136		)	(170		)	(98		)
	Income tax expense/(benefit)	63			(10		)	(84		)	—			(31		)
	Net Loss	168			(13		)	(52		)	(170		)	(67		)
	Less: Net (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	—			(3		)	4			(12		)	(11		)
	Net Income/(Loss) Attributable to NRG Energy, Inc.	$	168		$	(10	)	$	(56	)	$	(158	)	$	(56	)
	(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 March 31, 2015
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Net Income/(Loss)	$	83		$	(75	)	$	(126	)	$	(18	)	$	(136	)
	Other Comprehensive Income/(Loss), net of tax
	Unrealized (loss)/gain on derivatives, net	(7		)	11			(16		)	—			(12		)
	Foreign currency translation adjustments, net	—			(9		)	(2		)	—			(11		)
	Available-for-sale securities, net	—			(1		)	—			—			(1		)
	Defined benefit plan, net	(3		)	(1		)	11			—			7
	Other comprehensive (loss)/income	(10		)	—			(7		)	—			(17		)
	Comprehensive Income/(Loss)	73			(75		)	(133		)	(18		)	(153		)
	Less: Comprehensive income/(loss) attributable to noncontrolling interest and redeemable noncontrolling interest	—			(34		)	(6		)	11			(29		)
	Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	73			(41		)	(127		)	(29		)	(124		)
	Dividends for preferred shares	—			—			5			—			5
	Comprehensive Income/(Loss) Available for Common Stockholders	$	73		$	(41	)	$	(132	)	$	(29	)	$	(129	)
	(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 March 31, 2014
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
		(In millions)
	Net Income/(Loss)	$	168		$	(13	)	$	(52	)	$	(170	)	$	(67	)
	Other Comprehensive (Loss)/Income, net of tax
	Unrealized gain/(loss) on derivatives, net	6			(6		)	5			(14		)	(9		)
	Foreign currency translation adjustments, net	—			6			—			—			6
	Available-for-sale securities, net	—			—			4			2			6
	Defined benefit plan	2			—			—			—			2
	Other comprehensive income/(loss)	8			—			9			(12		)	5
	Comprehensive Income/(Loss)	176			(13		)	(43		)	(182		)	(62		)
	Less: Comprehensive (loss)/income attributable to noncontrolling interest and redeemable noncontrolling interest	—			(5		)	4			(14		)	(15		)
	Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	176			(8		)	(47		)	(168		)	(47		)
	Dividends for preferred shares	—			—			2			—			2
	Comprehensive Income/(Loss) Available for Common Stockholders	$	176		$	(8	)	$	(49	)	$	(168	)	$	(49	)
	(a)	All significant intercompany transactions have been eliminated in consolidation.
Condensed Consolidating Balance Sheets	NRG ENERGY, INC. AND SUBSIDIARIES
	CONDENSED CONSOLIDATING BALANCE SHEETS
	March 31, 2015
	(Unaudited)
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
	ASSETS	(In millions)
	Current Assets
	Cash and cash equivalents	$	13		$	1,378		$	773		$	—		$	2,164
	Funds deposited by counterparties	39			29			—			—			68
	Restricted cash	14			427			2			—			443
	Accounts receivable, net	936			240			3			—			1,179
	Inventory	505			604			—			—			1,109
	Derivative instruments	1,480			938			—			(389		)	2,029
	Cash collateral paid in support of energy risk management activities	246			154			—			—			400
	Accounts receivable - affiliate	8,656			2,103			(5,750		)	(5,002		)	7
	Deferred income taxes	—			93			95			—			188
	Renewable energy grant receivable	—			68			—			—			68
	Prepayments and other current assets	148			319			—			—			467
	Total current assets	12,037			6,353			(4,877		)	(5,391		)	8,122
	Net property, plant and equipment	8,260			13,847			194			(25		)	22,276
	Other Assets
	Investment in subsidiaries	422			2,542			21,907			(24,871		)	—
	Equity investments in affiliates	(18		)	841			39			(90		)	772
	Notes receivable, less current portion	—			58			221			(212		)	67
	Goodwill	2,072			448			—			—			2,520
	Intangible assets, net	859			1,637			1			(6		)	2,491
	Nuclear decommissioning trust fund	586			—			—			—			586
	Derivative instruments	318			321			1			(49		)	591
	Deferred income tax	(61		)	652			893			—			1,484
	Non-current assets held-for-sale	—			17			—			—			17
	Other non-current assets	112			681			611			—			1,404
	Total other assets	4,290			7,197			23,673			(25,228		)	9,932
	Total Assets	$	24,587		$	27,397		$	18,990		$	(30,644	)	$	40,330
	LIABILITIES AND STOCKHOLDERS’ EQUITY
	Current Liabilities
	Current portion of long-term debt and capital leases	$	1		$	445		$	231		$	(212	)	$	465
	Accounts payable	645			358			42			—			1,045
	Accounts payable — affiliate	2,336			2,853			(576		)	(4,613		)	—
	Derivative instruments	1,439			834			—			(389		)	1,884
	Cash collateral received in support of energy risk management activities	39			29			—			—			68
	Accrued expenses and other current liabilities	233			496			318			—			1,047
	Total current liabilities	4,693			5,015			15			(5,214		)	4,509
	Other Liabilities
	Long-term debt and capital leases	308			11,456			8,286			—			20,050
	Nuclear decommissioning reserve	314			—			—			—			314
	Nuclear decommissioning trust liability	328			—			—			—			328
	Deferred income taxes	1,284			(1,039		)	(225		)	—			20
	Derivative instruments	369			330			—			(49		)	650
	Out-of-market contracts	107			1,114			—			—			1,221
	Other non-current liabilities	490			767			292			—			1,549
	Total non-current liabilities	3,200			12,628			8,353			(49		)	24,132
	Total liabilities	7,893			17,643			8,368			(5,263		)	28,641
	2.822% convertible perpetual preferred stock	—			—			293			—			293
	Redeemable noncontrolling interest in subsidiaries	—			19			—			—			19
	Stockholders’ Equity	16,694			9,735			10,329			(25,381		)	11,377
	Total Liabilities and Stockholders’ Equity	$	24,587		$	27,397		$	18,990		$	(30,644	)	$	40,330
	(a)	All significant intercompany transactions have been eliminated in consolidation.
	NRG ENERGY, INC. AND SUBSIDIARIES
	CONDENSED CONSOLIDATING BALANCE SHEETS
	December 31, 2014
		Guarantor Subsidiaries			Non-Guarantor Subsidiaries			NRG Energy, Inc.			Eliminations(a)			Consolidated
								(Note Issuer)
	ASSETS	(In millions)
Current Assets
Cash and cash equivalents	$	18		$	1,455		$	643		$	—		$	2,116
Funds deposited by counterparties	9			63			—			—			72
Restricted cash	5			451			1			—			457
Accounts receivable, net	924			392			6			—			1,322
Inventory	537			710			—			—			1,247
Derivative instruments	1,657			1,209			—			(441		)	2,425
Accounts receivable - affiliate	7,449			1,988			(5,991		)	(3,437		)	9
Cash collateral paid in support of energy risk management activities	114			73			—			—			187
Renewable energy grant receivable	—			134			1			—			135
Prepayments and other current assets	94			175			343			—			612
Total current assets	10,807			6,650			(4,997		)	(3,878		)	8,582
Net Property, Plant and Equipment	8,344			13,877			171			(25		)	22,367
Other Assets
Investment in subsidiaries	140			2,293			23,410			(25,843		)	—
Equity investments in affiliates	(18		)	891			—			(102		)	771
Capital leases and notes receivable, less current portion	1			60			109			(98		)	72
Goodwill	1,921			653			—			—			2,574
Intangible assets, net	765			1,806			2			(6		)	2,567
Nuclear decommissioning trust fund	585			—			—			—			585
Deferred income taxes	(247		)	816			837			—			1,406
Derivative instruments	242			288			1			(51		)	480
Non-current assets held for sale	—			17			—			—			17
Other non-current assets	113			623			508			—			1,244
Total other assets	3,502			7,447			24,867			(26,100		)	9,716
Total Assets	$	22,653		$	27,974		$	20,041		$	(30,003	)	$	40,665
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current Liabilities
Current portion of long-term debt and capital leases	$	1		$	444		$	127		$	(98	)	$	474
Accounts payable	598			416			46			—			1,060
Accounts payable — affiliate	1,588			2,447			(598		)	(3,437		)	—
Deferred Income Taxes	7			—			(7		)	—			—
Derivative instruments	1,532			963			—			(441		)	2,054
Cash collateral received in support of energy risk management activities	9			63			—			—			72
Accrued expenses and other current liabilities	283			498			418			—			1,199
Total current liabilities	4,018			4,831			(14		)	(3,976		)	4,859
Other Liabilities
Long-term debt and capital leases	307			11,226			8,367			—			19,900
Nuclear decommissioning reserve	310			—			—			—			310
Nuclear decommissioning trust liability	333			—			—			—			333
Deferred income taxes	1,036			(1,012		)	(3		)	—			21
Derivative instruments	248			241			—			(51		)	438
Out-of-market contracts	111			1,133			—			—			1,244
Other non-current liabilities	465			795			314			—			1,574
Total non-current liabilities	2,810			12,383			8,678			(51		)	23,820
Total Liabilities	6,828			17,214			8,664			(4,027		)	28,679
2.822% Preferred Stock	—			—			291			—			291
Redeemable noncontrolling interest in subsidiaries	—			19			—			—			19
Stockholders’ Equity	15,825			10,741			11,086			(25,976		)	11,676
Total Liabilities and Stockholders’ Equity	$	22,653		$	27,974		$	20,041		$	(30,003	)	$	40,665
(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 Three Months Ended March 31, 2015
	(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	$	820		$	(430	)	$	(539	)	$	409		$	260
	Cash Flows from Investing Activities
	(Payments for)/proceeds from intercompany loans to subsidiaries	(737		)	328			409			—			—
	Acquisition of businesses, net of cash acquired	—			(1		)	—			—			(1		)
	Capital expenditures	(89		)	(157		)	(6		)	—			(252		)
	Increase in restricted cash, net	—			(11		)	—			—			(11		)
	Decrease/(increase) in restricted cash — U.S. DOE projects	—			24			1			—			25
	Decrease in notes receivable	—			5			—			—			5
	Investments in nuclear decommissioning trust fund securities	(193		)	—			—			—			(193		)
	Proceeds from sales of nuclear decommissioning trust fund securities	196			—			—			—			196
	Proceeds from renewable energy grants	—			2			—			—			2
	Other	(2		)	(2		)	(37		)	—			(41		)
	Net Cash Used by Investing Activities	(825		)	188			367			—			(270		)
	Cash Flows from Financing Activities
	Proceeds/(payments) from intercompany loans	—			—			409			(409		)	—
	Payment of dividends to common and preferred stockholders	—			—			(51		)	—			(51		)
	Payment for treasury stock	—			—			(79		)	—			(79		)
	Net payments for settlement of acquired derivatives that include financing elements	—			40			—			—			40
	Proceeds from issuance of long-term debt	—			221			27			—			248
	Contributions to, net of distributions from, noncontrolling interest in subsidiaries	—			(25		)	—			—			(25		)
	Proceeds from issuance of common stock	—			—			1			—			1
	Payments for short and long-term debt	—			(89		)	(5		)	—			(94		)
	Net Cash Provided by Financing Activities	—			147			302			(409		)	40
	Effect of exchange rate changes on cash and cash equivalents	—			18			—			—			18
	Net (Decrease)/Increase in Cash and Cash Equivalents	(5		)	(77		)	130			—			48
	Cash and Cash Equivalents at Beginning of Period	18			1,455			643			—			2,116
	Cash and Cash Equivalents at End of Period	$	13		$	1,378		$	773		$	—		$	2,164
	(a)	All significant intercompany transactions have been eliminated in consolidation.
	NRG ENERGY, INC. AND SUBSIDIARIES
	CONDENSED CONSOLIDATING STATEMENTS OF CASH FLOWS
	For the Three Months Ended March 31, 2014
	(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 by Operating Activities	$	446		$	430		$	(886	)	$	401		$	391
	Cash Flows from Investing Activities
	Intercompany loans to subsidiaries	(405		)	4			401			—			—
	Acquisition of businesses, net of cash acquired	—			(25		)	(193		)	—			(218		)
	Capital expenditures	(73		)	(162		)	(2		)	—			(237		)
	(Increase)/decrease in restricted cash, net	—			3			—			—			3
	Increase in restricted cash — U.S. DOE projects	(4		)	60			—			—			56
	Decrease/(increase) in notes receivable	—			1			—			—			1
	Investments in nuclear decommissioning trust fund securities	(188		)	—			—			—			(188		)
	Proceeds from sales of nuclear decommissioning trust fund securities	183			—			—			—			183
	Proceeds from renewable energy grants	—			387			—			—			387
	Proceeds from sale of assets	—			—			77			—			77
	Cash proceeds to fund cash grant bridge loan payment	—			57			—			—			57
	Other	7			(4		)	—			—			3
	Net Cash (Used)/Provided by Investing Activities	(480		)	321			283			—			124
	Cash Flows from Financing Activities
	Proceeds from intercompany loans	—			—			401			(401		)	—
	Payment of dividends to preferred stockholders	—			—			(41		)	—			(41		)
	Net (payment for)/receipts from settlement of acquired derivatives that include financing elements	—			(223		)	—			—			(223		)
	Proceeds from issuance of long-term debt	—			464			1,100			—			1,564
Proceeds from issuance of common stock	—			—			3			—			3
Sale proceeds and other contributions from noncontrolling interest in subsidiaries	—			9			—			—			9
Payment of debt issuance costs	—			(9		)	(14		)	—			(23		)
Payments for short and long-term debt	—			(405		)	(468		)	—			(873		)
Net Cash (Used)/Provided by Financing Activities	—			(164		)	981			(401		)	416
Effect of exchange rate changes on cash and cash equivalents	—			2			—			—			2
Net (Decrease)/Increase in Cash and Cash Equivalents	(34		)	589			378			—			933
Cash and Cash Equivalents at Beginning of Period	56			870			1,328			—			2,254
Cash and Cash Equivalents at End of Period	$	22		$	1,459		$	1,706		$	—		$	3,187
(a)	All significant intercompany transactions have been eliminated in consolidation.

Basis_of_Presentation_Basis_of

Basis of Presentation Basis of Presentation (Details)	Mar. 31, 2015
	MW
Basis of Presentation
Power Generation Capacity, Megawatts	51,000

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Apr. 09, 2015
Noncontrolling Interest [Line Items]
Capital expenditures accrued and unpaid	$40
Stockholders' Equity Attributable to Noncontrolling Interest	1,848		1,914
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	-24
Non-cash Increase to Noncontrolling interest	14
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	-29	-15
NRG Yield, Inc.
Noncontrolling Interest [Line Items]
Sale of Assets Under Common Control	-27
NRG RPV Holdco [Member] | NRG Yield, Inc.
Noncontrolling Interest [Line Items]
Capital Contribution to Equity Method Investment				$26

Summary_of_Significant_Account4

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details 2) (USD $)	3 Months Ended	0 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Apr. 09, 2015	Dec. 31, 2014
	MW	generatingunit
		MW
Noncontrolling Interest [Line Items]
Power Generation Capacity, Megawatts	51,000
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount	$19		$19
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	14
Existing Portfolio of Leases [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Number of Solar Leases in Portfolio		2,200
Power Generation Capacity, Megawatts		17
Remaining Lease Term		17 years
In-Development Portfolio of Leases [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Power Generation Capacity, Megawatts		48
Remaining Lease Term		20 years
In-Development Portfolio of Leases Tranche 2 [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Power Generation Capacity, Megawatts		42
Remaining Lease Term		20 years
Minimum [Member] | In-Development Portfolio of Leases [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Number of Solar Leases in Portfolio		6,000
Minimum [Member] | In-Development Portfolio of Leases Tranche 2 [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Number of Solar Leases in Portfolio		5,500
Maximum [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Equity Method Investments		150
Maximum [Member] | In-Development Portfolio of Leases [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Number of Solar Leases in Portfolio		7,000
Maximum [Member] | In-Development Portfolio of Leases Tranche 2 [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Number of Solar Leases in Portfolio		6,500
NRG [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Economic Interest in Entity		5.00%
NRG Yield, Inc. [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Capital Contribution to Equity Method Investment		26
Economic Interest in Entity		95.00%
Scenario, Plan [Member] | NRG [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Economic Interest in Entity		95.00%
Scenario, Plan [Member] | NRG Yield, Inc. [Member] | NRG RPV Holdco [Member]
Noncontrolling Interest [Line Items]
Economic Interest in Entity		5.00%

Business_Acquisitions_and_Disp2

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 1 - 2015 Sale to Yield) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Jan. 02, 2015	Jun. 30, 2014
In Millions, unless otherwise specified
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term Debt	$20,509	$20,366
ROFO Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration Paid for Sale of Assets Under Common Control			489	357
Long-term Debt			737	612
Assets Transferred, Carrying Value			405	236
Working Capital Adjustment [Member] | ROFO Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration Paid for Sale of Assets Under Common Control			$9	$8

Business_Acquisitions_and_Disp3

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 2 - Sabine) (USD $)	0 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Dec. 03, 2014	Dec. 31, 2014	Mar. 31, 2015	Dec. 02, 2014
			MW	MW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Power Generation Capacity, Megawatts			51,000
Sabine CoGen, LP [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of Ownership Sold of Subsidiary				50.00%
Power Generation Capacity, Megawatts				105
Proceeds from Sale of Equity Method Investments	$35
Equity Method Investment, Realized Gain (Loss) on Disposal		$18

Business_Acquisitions_and_Disp4

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 3 - Alta Wind) (USD $)	0 Months Ended	3 Months Ended	0 Months Ended
In Millions, except Share data, unless otherwise specified	Aug. 13, 2014	Mar. 31, 2015	Jul. 30, 2014	Dec. 31, 2014	Aug. 12, 2014	Aug. 05, 2014
					MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts		51,000
Long-term Debt		$20,509		$20,366
Alta Wind Portfolio [Member]
Business Acquisition [Line Items]
Percentage of Ownership					100.00%
Power Generation Capacity, Megawatts					947
Payments to Acquire Businesses, Gross	923
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt					870
Business Acquisition, Consideration Transferred, Working Capital					53
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		22		22
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment				1,304
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles				1,177
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets				2,552
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt				1,591
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current and Non-Current Liabilities				38
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities				1,629
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets				49
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Other Assets		-2
Business Acquisition, Purchase Price Allocation, Other Assets, Adjusted		47
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment		6
Business Acquisition, Purchase Price Allocation, Property, Plant and Equipment, Adjusted		1,310
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles		-6
Business Acquisition, Purchase Price Allocation, Intangible Assets, Other than Goodwill, Adjusted		1,171
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Assets		-2
Business Acquisition, Purchase Price Allocation, Assets Acquired, Adjusted		2,550
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Liabilities Longterm Debt		0
Business Acquisition, Purchase Price Allocation, Noncurrent Liabilities, Long-term Debt, Adjusted		1,591
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current and Noncurrent Liabilities		-2
Business Acquisition, Purchase Price Allocation, Current and Non-current Liabilities, Adjusted		36
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities		-2
Business Acquisition, Purchase Price Allocation, Liabilities Assumed, Adjusted		1,627
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net				923
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Net Assets Acquired		0
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net Adjusted		923
NRG Yield Operating LLC [Member]
Business Acquisition [Line Items]
Long-term Debt						500
Debt Instrument, Interest Rate, Stated Percentage						5.38%
NRG Yield, Inc. | Common Class A [Member]
Business Acquisition [Line Items]
Shares, Issued			12,075,000
Proceeds from Issuance or Sale of Equity			$630

Business_Acquisitions_and_Disp5

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 4 - Petra Nova) (USD $)	0 Months Ended
In Millions, unless otherwise specified	Jul. 07, 2014	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jul. 03, 2014
		MW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Power Generation Capacity, Megawatts		51,000
Long-term Debt		$20,509	$20,366
Petra Nova Parish Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of Ownership Sold of Subsidiary					50.00%
Capital Contribution to Equity Method Investment	35
Proceeds from Divestiture of Interest in Subsidiaries and Affiliates	76
Capital Contributions From Partners in Equity Method Investment				300
Petra Nova Parish Holdings [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Power Generation Capacity, Megawatts				75
Department of Energy [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount guaranteed to borrow by US DOE				167
JBIC and Mizuho [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term Debt				$250

Business_Acquisitions_and_Disp6

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 5 - 2014 Sale to Yield) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Jan. 02, 2015	Jun. 30, 2014
In Millions, unless otherwise specified
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term Debt	$20,509	$20,366
ROFO Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration Paid for Sale of Assets Under Common Control			489	357
Long-term Debt			737	612
Assets Transferred, Carrying Value			405	236
Base Purchase Price [Member] | ROFO Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration Paid for Sale of Assets Under Common Control				349
Working Capital Adjustment [Member] | ROFO Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration Paid for Sale of Assets Under Common Control			$9	$8

Business_Acquisitions_and_Disp7

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 6 - Dominion) (USD $)	0 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill		$2,520	$2,574
Dominion [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred	192
Business Acquisitions, Consideration Transferred, Purchase Price	165
Business Acquisition, Consideration Transferred, Working Capital	27
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	40
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	14
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Derivative Assets	21
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	47
Goodwill	91
Business Acquisition, Goodwill, Expected Tax Deductible Amount	8
Customer Relationships [Member] | Dominion [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	64
Trade Names [Member] | Dominion [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	$9
Scenario, Plan [Member] | Dominion [Member]
Business Acquisition [Line Items]
Business Acquisition, Customers Acquired	540,000

Business_Acquisitions_and_Disp8

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 7 - EME 1) (USD $)	3 Months Ended		0 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Apr. 02, 2014	Dec. 31, 2014
	MW		MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts	51,000
Payments to Acquire Businesses, Net of Cash Acquired	$1	$218
Edison Mission Energy [Member]
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts			8,000
Business Combination, Consideration Transferred			3,500
Business Combination, Estimated Consideration Transferred, Estimated Liabilities Incurred			700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			1,249	1,249
Common Stock [Member] | Edison Mission Energy [Member]
Business Acquisition [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares			12,671,977
Through 2034 [Member]
Business Acquisition [Line Items]
Repayments of Long-term Capital Lease Obligations		405
EME [Member]
Business Acquisition [Line Items]
Environmental Capital Expenditures, Estimated Total		$350

Business_Acquisitions_and_Disp9

Business Acquisitions and Dispositions Business Acquisitions and Dispositions (Details 8 - EME 2) (USD $)	3 Months Ended		0 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Apr. 02, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$2,520			$2,574
Acquisition-related transaction and integration costs	10	12
Edison Mission Energy [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			3,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	1,422			1,422
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment				2,438
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment	-3
Business Acquisition, Purchase Price Allocation, Property, Plant and Equipment, Adjusted	2,435
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles	0
Business Acquisition, Purchase Price Allocation, Intangible Assets, Other than Goodwill, Adjusted	172
Goodwill				334
Goodwill, Purchase Accounting Adjustments	-56
Goodwill, Adjusted	278
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets				773
Business Acquisition, Purchase Price Allocation, Other Assets, Adjusted	796
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets				5,863
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Assets	13
Business Acquisition, Purchase Price Allocation, Assets Acquired, Adjusted	5,876
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current and Non-Current Liabilities				629
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current and Noncurrent Liabilities	13
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Out-of-market Contracts and Leases				159
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Out of Market Contracts and Leases	0
Business Acquisition, Purchase Price Allocation, Out of Market Contracts and Leases, Adjusted	159
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			1,249	1,249
Business Acquisition, Purchase Price Allocation, Noncurrent Liabilities, Long-term Debt, Adjusted	1,249
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities				2,037
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Financial Liabilities	13
Business Acquisition, Purchase Price Allocation, Liabilities Assumed, Adjusted	2,050
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value				352
Business Acquisition, Purchase Price Allocation, Noncontrolling Interest, Adjusted	352
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Net Assets Acquired	0
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net Adjusted	3,474
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets				724
Business Combination, Provisional Information, Initial Accounting Incomplete, Current Assets	72
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles				172
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Assets	0
Business Acquisition, Purchase Price Allocation, Noncurrent Assets, Adjusted	773
Business Acquisition, Purchase Price Allocation, Current and Non-current Liabilities, Adjusted	642
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Liabilities Longterm Debt	0
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncontrolling Interest	0
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest				$3,474

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details 1) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term debt, including current portion	$20,509		$20,366
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes receivable	86	[1]	91	[1]
Long-term debt, including current portion	20,509		20,366
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Notes receivable	86	[1]	91	[1]
Long-term debt, including current portion	$20,679		$20,361
[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 - Recurring FV) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, unless otherwise specified
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets	$2,620		$2,905
Derivative Liabilities	2,534		2,492
Commodity contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets	2,620		2,902
Derivative Liabilities	2,336		2,327
Interest rate contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			2
Derivative Liabilities	-198		165
Equity Contract [Member]
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			1
Fair Value | Fair Value, Measurements, Recurring
Fair Value Assets and Liabilities, Measured on Recurring Basis
Debt securities	18		18
Available-for-sale Securities	24		30
Other	31	[1]	32	[2]
Total assets	3,280		3,571
Total liabilities	2,534		2,492
Fair Value | Fair Value, Measurements, Recurring | Commodity contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets	2,620		2,902
Derivative Liabilities	2,336		2,327
Fair Value | Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			2
Derivative Liabilities	198		165
Fair Value | Fair Value, Measurements, Recurring | Equity Contract [Member]
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			1
Fair Value | Fair Value, Measurements, Recurring | Cash and cash equivalents
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	5		14
Fair Value | Fair Value, Measurements, Recurring | U.S. government and federal agency obligations
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	53		47
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	1		1
Fair Value | Fair Value, Measurements, Recurring | Federal agency mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	71		74
Fair Value | Fair Value, Measurements, Recurring | Commercial mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	24		25
Fair Value | Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	84		78
Fair Value | Fair Value, Measurements, Recurring | Equity securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	347		344
Fair Value | Fair Value, Measurements, Recurring | Foreign government fixed income securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	2		3
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring
Fair Value Assets and Liabilities, Measured on Recurring Basis
Debt securities	18		18
Available-for-sale Securities	0		0
Other	11	[1]	11	[2]
Total assets	347		391
Total liabilities	230		230
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Commodity contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets	264		309
Derivative Liabilities	230		230
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			0
Derivative Liabilities	0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Equity Contract [Member]
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			1
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Cash and cash equivalents
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | U.S. government and federal agency obligations
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Federal agency mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Commercial mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Equity securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	54		52
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring | Foreign government fixed income securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring
Fair Value Assets and Liabilities, Measured on Recurring Basis
Debt securities	0		0
Available-for-sale Securities	0		0
Other	0	[1]	0	[2]
Total assets	1,542		1,700
Total liabilities	1,340		1,258
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Commodity contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets	1,358		1,515
Derivative Liabilities	1,142		1,093
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			2
Derivative Liabilities	198		165
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Equity Contract [Member]
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Cash and cash equivalents
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | U.S. government and federal agency obligations
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	3		3
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Federal agency mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	71		74
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Commercial mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	24		25
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	84		78
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Equity securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring | Foreign government fixed income securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	2		3
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring
Fair Value Assets and Liabilities, Measured on Recurring Basis
Debt securities	0		0
Available-for-sale Securities	24		30
Other	20	[1]	21	[2]
Total assets	1,391		1,480
Total liabilities	964		1,004
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Commodity contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets	998		1,078
Derivative Liabilities	964		1,004
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			0
Derivative Liabilities	0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Equity Contract [Member]
Fair Value Assets and Liabilities, Measured on Recurring Basis
Derivative Assets			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Cash and cash equivalents
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	5		14
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | U.S. government and federal agency obligations
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	50		44
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	1		1
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Federal agency mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Commercial mortgage-backed securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Equity securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	293		292
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring | Foreign government fixed income securities
Fair Value Assets and Liabilities, Measured on Recurring Basis
Decommissioning Fund Investments	$0		$0
[1]	Consists primarily of mutual funds held in a Rabbi Trust for non-qualified deferred compensation plans for certain former employees and a total return swap that does not meet the definition of a derivative.
[2]	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 - Level 3 FV) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014		Dec. 31, 2013
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
No transfers during the three and six months ended June 30, 2013 and 2013 (Level 2 to Level 1)	0		0
Fair Value, Inputs, Level 3 [Member]
Fair Value Asset and Liabilities, Measured on Recurring Basis Unobservable Input, Changes
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	117		108		161		95
Total gains/(losses) - realized/unrealized:
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	-55		17
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			2
Included in nuclear decommissioning obligation	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	-4		-21
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Contracts Acquired			3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	15	[1]	18	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	-2	[1]	-6	[1]
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	-20		19
Fair Value, Inputs, Level 3 [Member] | Debt Securities
Fair Value Asset and Liabilities, Measured on Recurring Basis Unobservable Input, Changes
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	18		18		18		16
Total gains/(losses) - realized/unrealized:
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			2
Included in nuclear decommissioning obligation	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Contracts Acquired			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	[1]	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	0	[1]	0	[1]
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
Fair Value, Inputs, Level 3 [Member] | Other Financial Instrument [Member]
Fair Value Asset and Liabilities, Measured on Recurring Basis Unobservable Input, Changes
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	11		11		11		10
Total gains/(losses) - realized/unrealized:
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Included in nuclear decommissioning obligation	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Contracts Acquired			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	[1]	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	0	[1]	0	[1]
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
Fair Value, Inputs, Level 3 [Member] | Trust Fund Investments
Fair Value Asset and Liabilities, Measured on Recurring Basis Unobservable Input, Changes
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	54		56		52		56
Total gains/(losses) - realized/unrealized:
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Included in nuclear decommissioning obligation	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Contracts Acquired			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	[1]	0	[1]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	0	[1]	0	[1]
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
Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Asset and Liabilities, Measured on Recurring Basis Unobservable Input, Changes
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs	34	[2]	23	[2]	80	[2]	13	[2]
Total gains/(losses) - realized/unrealized:
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	-55	[2]	16	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			0	[2]
Included in nuclear decommissioning obligation	0	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	-4	[2]	-21	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Contracts Acquired			3	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	15	[1],[2]	18	[1],[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	-2	[1],[2]	-6	[1],[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	($20)	[2]	$19	[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
	Mar. 31, 2015
Concentration of Credit Risk
Total derivative assets valued with prices provied by models and other valuation techniques (as a percent)	10.00%
Total derivative liabilities valued with prices provied by models and other valuation techniques (as a percent)	9.00%
Valuation Allowances and Reserves, Balance	$5,000,000
Increase in fair value as a result of the credit reserve, portion recorded in OCI	-3,000,000
Increase in fair value as a result of the credit reserve, portion recorded in operating revenue and cost of operations	-2,000,000
Counterparty credit exposure to a portion of the Company's counterparties	842,000,000
Collateral held (cash and letters of credit) against counterparty credit exposure to a portion of the Company's counterparties	84,000,000
Net counterparty credit exposure to a portion of the Company's counterparties	763,000,000
Company's exposure before collateral is expected to roll off by the end of 2014 (as a percent)	91.00%
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	290,000,000
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	3,300,000,000
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)	2.00%	[1],[2]
External Credit Rating, Non Investment Grade [Member]
Concentration of Credit Risk
Net Exposure (as a percent)	2.00%	[1]
Financial institutions
Concentration of Credit Risk
Net Exposure (as a percent)	48.00%	[1]
Utilities, energy merchants, marketers and other
Concentration of Credit Risk
Net Exposure (as a percent)	32.00%	[1]
ISOs
Concentration of Credit Risk
Net Exposure (as a percent)	20.00%	[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	$2,300,000,000
[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 $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Nuclear decommissioning trust fund disclosure
Fair Value	$586		$585
Unrealized Gains	218		218
Unrealized Losses	1		2
Realized gains	6	3
Available-for-sale Securities, Gross Realized Losses	2	1
Proceeds from Sale of Available-for-sale Securities	196	183
Cash and Cash Equivalents [Member]
Nuclear decommissioning trust fund disclosure
Fair Value	5		14
Unrealized Gains	0		0
Unrealized Losses	0		0
Weighted-average Maturities (In years)	0 years		0 years
U.S. government and federal agency obligations
Nuclear decommissioning trust fund disclosure
Fair Value	53		47
Unrealized Gains	3		2
Unrealized Losses	0		0
Weighted-average Maturities (In years)	10 years		11 years
Federal agency mortgage-backed securities
Nuclear decommissioning trust fund disclosure
Fair Value	71		74
Unrealized Gains	2		2
Unrealized Losses	0		0
Weighted-average Maturities (In years)	24 years		25 years
Commercial mortgage-backed securities
Nuclear decommissioning trust fund disclosure
Fair Value	24		25
Unrealized Gains	0		0
Unrealized Losses	1		1
Weighted-average Maturities (In years)	30 years		30 years
Corporate debt securities
Nuclear decommissioning trust fund disclosure
Fair Value	84		78
Unrealized Gains	2		2
Unrealized Losses	0		1
Weighted-average Maturities (In years)	10 years		11 years
Equity securities
Nuclear decommissioning trust fund disclosure
Fair Value	347		344
Unrealized Gains	211		211
Unrealized Losses	0		0
Weighted-average Maturities (In years)	0 years		0 years
Foreign government fixed income securities
Nuclear decommissioning trust fund disclosure
Fair Value	2		3
Unrealized Gains	0		1
Unrealized Losses	$0		$0
Weighted-average Maturities (In years)	15 years		16 years

Accounting_for_Derivative_Inst2

Accounting for Derivative Instruments and Hedging Activities (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
	T	T
Fair Value of Derivative Instrument
Derivative Assets	2,620	2,905
Derivative Liabilities	2,534	2,492
Derivatives Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	2
Derivative Liabilities	148	129
Derivatives Not Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	2,620	2,903
Derivative Liabilities	2,386	2,363
Interest rate contracts current | Derivatives Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	0
Derivative Liabilities	51	55
Interest rate contracts current | Derivatives Not Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	0
Derivative Liabilities	9	8
Interest rate contracts long-term | Derivatives Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	2
Derivative Liabilities	97	74
Interest rate contracts long-term | Derivatives Not Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	0
Derivative Liabilities	41	28
Commodity contracts current | Derivatives Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	0
Derivative Liabilities	0	0
Commodity contracts current | Derivatives Not Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	2,029	2,425
Derivative Liabilities	1,824	1,991
Commodity contracts long-term | Derivatives Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	0
Derivative Liabilities	0	0
Commodity contracts long-term | Derivatives Not Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	591	477
Derivative Liabilities	512	336
Equity Contract [Member]
Fair Value of Derivative Instrument
Derivative Assets		1
Equity Contract [Member] | Derivatives Not Designated as Cash Flow Hedges
Fair Value of Derivative Instrument
Derivative Assets	0	1
Derivative Liabilities	0	0
Emissions [Member] | Short Ton [Member]
Volumetric Underlying Derivative Transactions
Derivative, Nonmonetary Notional Amount, Mass	4,000,000	2,000,000
Coal [Member] | Short Ton [Member]
Volumetric Underlying Derivative Transactions
Derivative, Nonmonetary Notional Amount, Mass	48,000,000	57,000,000
Natural Gas [Member] | MMbtu [Member]
Volumetric Underlying Derivative Transactions
Derivative, Nonmonetary Notional Amount, Energy Measure	35,000,000	58,000,000
Oil [Member] | Barrel [Member]
Volumetric Underlying Derivative Transactions
Derivative, Nonmonetary Notional Amount, Volume	1,000,000	1,000,000
Power [Member] | M Wh [Member]
Volumetric Underlying Derivative Transactions
Derivative, Nonmonetary Notional Amount, Energy Measure	52,000,000	56,000,000
Capacity [Member] | MW/Day [Member]
Volumetric Underlying Derivative Transactions
Derivative, Nonmonetary Notional Amount, Energy Measure	1,000,000	0
Interest [Member] | United States of America, Dollars
Volumetric Underlying Derivative Transactions
Derivative, Notional Amount	3,399	3,440
Equity [Member] | Shares [Member]
Fair Value of Derivative Instrument
Derivative, Non-monetary Notional Amount, Other	2	2

Accounting_for_Derivative_Inst3

Accounting for Derivative Instruments and Hedging Activities (Details 2 - Offsetting Derivatives) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative Assets	$2,620	$2,905
Cash Collateral (Held)	-68	-72
Gross Amounts of Recognized Derivative Liabilities	-2,534	-2,492
Cash Collateral Posted	400	187
Gross Amounts of Recognized Assets / Liabilities	86	413
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset	0	0
Derivative, Collateral, Obligation to Return Cash Net Of Derivative, Collateral, Right to Reclaim Cash	-9	-45
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral	77	368
Commodity contracts
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative Assets	2,620	2,902
Derivative Instruments	-2,092	-2,155
Cash Collateral (Held)	-64	-72
Net Amount	464	675
Gross Amounts of Recognized Derivative Liabilities	-2,336	-2,327
Derivative Instruments	2,092	2,155
Cash Collateral Posted	55	27
Derivative Liability, Fair Value, Amount Offset Against Collateral	189	145
Gross Amounts of Recognized Assets / Liabilities	284	575
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset	0	0
Derivative, Collateral, Obligation to Return Cash Net Of Derivative, Collateral, Right to Reclaim Cash	-9	-45
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral	275	530
Interest rate contracts
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative Assets		2
Derivative Instruments		-2
Cash Collateral (Held)		0
Net Amount		0
Gross Amounts of Recognized Derivative Liabilities	198	-165
Derivative Instruments	0	2
Cash Collateral Posted	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	-198	163
Gross Amounts of Recognized Assets / Liabilities		-163
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset		0
Derivative, Collateral, Obligation to Return Cash Net Of Derivative, Collateral, Right to Reclaim Cash		0
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral		-163
Equity Contract [Member]
Offsetting of Derivatives by Counterparty Master Agreement Level and Collateral Received or Paid
Derivative Assets		1
Derivative Instruments		0
Cash Collateral (Held)		0
Net Amount		$1

Accounting_for_Derivative_Inst4

Accounting for Derivative Instruments and Hedging Activities (Details 3 - AOCI) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Derivative
Derivative, Net Liability Position, Collateral Required Contracts with Credit Rating Contingent Feature	$39
Derivative Asset, Fair Value, Gross Asset	2,620		2,905
Derivative Liability, Fair Value, Gross Liability	2,534		2,492
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax
Accumulated OCI beginning balance	-68	-23
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	2	-1
Mark-to-market of cash flow hedge accounting contracts	-18	-8
Accumulated OCI ending balance, net of tax	-84	-32
Gains/(losses) expected to be realized from OCI during the next 12 months, net of tax	-14	-14
Accumulated OCI ending balance, tax	50	17
Gains/(losses) expected to be realized from OCI during the next 12 months, tax	7	7
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net	0
Commodity contracts
Derivative
Derivative Asset, Fair Value, Gross Asset	2,620		2,902
Derivative Liability, Fair Value, Gross Liability	2,336		2,327
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax
Accumulated OCI beginning balance	-1	-1
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0
Mark-to-market of cash flow hedge accounting contracts	0	0
Accumulated OCI ending balance, net of tax	-1	-1
Gains/(losses) expected to be realized from OCI during the next 12 months, net of tax	-1	-1
Interest rate contracts
Derivative
Derivative Asset, Fair Value, Gross Asset			2
Derivative Liability, Fair Value, Gross Liability	-198		165
Effects of ASC 815 on NRG's Accumulated OCI Balance Attributable to Cash Flow Hedge Derivatives, net of tax
Accumulated OCI beginning balance	-67	-22
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	2	-1
Mark-to-market of cash flow hedge accounting contracts	-18	-8
Accumulated OCI ending balance, net of tax	-83	-31
Gains/(losses) expected to be realized from OCI during the next 12 months, net of tax	($13)	($13)

Accounting_for_Derivative_Inst5

Accounting for Derivative Instruments and Hedging Activities Accounting for Derivative Instruments and Hedging Activities (Details 4 - mark to market) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Unrealized mark-to-market results
Reversal of previously recognized unrealized losses/(gains) on settled positions related to economic hedges	($114)	$3
Reversal of loss positions acquired as part of the acquisition	-26	-78
Net unrealized gains/(losses) on open positions related to economic hedges	138	193
Total unrealized mark-to-market gains/(losses) for economic hedging activities	-278	-268
Reversal of previously recognized unrealized (gains) losses on settled positions related to trading activity	-21	0
Reversal of Previously Unrecognized Unrealized Gain Loss Acquired as Part of Acquisition Trading Activity	-7	-1
Net unrealized gains on open positions related to trading activity	6	16
Total unrealized mark-to-market gains for trading activity	-22	15
Impact of derivative instruments on statement of operations
Total unrealized gains/(losses)	-300	-253
Credit Risk Related Contingent Features
Derivative Liability, Fair Value of Collateral	131
Derivative, Net Liability Position, Collateral Required Contracts with Credit Rating Contingent Feature	39
Collateral due on net liability position that has not been called by a certain marginable agreement counterparty	8
Commodity contracts
Impact of derivative instruments on statement of operations
Total unrealized gains/(losses)	-300	-253
Commodity contracts | Sales [Member]
Impact of derivative instruments on statement of operations
Total unrealized gains/(losses)	-109	-316
Commodity contracts | Cost of Sales [Member]
Impact of derivative instruments on statement of operations
Total unrealized gains/(losses)	-191	63
Interest rate contracts
Impact of derivative instruments on statement of operations
Total unrealized gains/(losses)	($14)	($4)

Debt_and_Capital_Leases_Detail

Debt and Capital Leases (Details 1 - Debt Table) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014	Jan. 27, 2014
Debt and Capital Leases
Long-term Debt	$20,509		$20,366
Subtotal	20,515		20,374
Less current maturities	465		474
Total long-term debt and capital leases	20,050		19,900
Interest rate, variable basis	3 month LIBOR
Recourse Debt
Debt and Capital Leases
Long-term Debt	8,823		8,800
Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	11,686		11,566
Convertible Debt, Fair Value Disclosures	327		326
Senior notes, due 2018 | Recourse Debt
Debt and Capital Leases
Long-term Debt	1,130		1,130
Interest rate, stated rate	7.63%	[1]
Senior notes, due 2020 | Recourse Debt
Debt and Capital Leases
Long-term Debt	1,063		1,063
Interest rate, stated rate	8.25%	[1]
Senior notes, due 2021 | Recourse Debt
Debt and Capital Leases
Long-term Debt	1,128		1,128
Interest rate, stated rate	7.88%	[1]
Senior Notes Due In 2022 [Member] | Recourse Debt
Debt and Capital Leases
Long-term Debt	1,100		1,100
Interest rate, stated rate	6.25%	[1]		6.25%
Senior notes, due 2023 | Recourse Debt
Debt and Capital Leases
Long-term Debt	990		990
Interest rate, stated rate	6.63%	[1]
Senior Notes 2024 [Member] | Recourse Debt
Debt and Capital Leases
Long-term Debt	1,000		1,000
Interest rate, stated rate	6.25%	[1]
Term loan facility, due 2018 | Recourse Debt
Debt and Capital Leases
Long-term Debt	1,978		1,983
Indian River Power LLC, tax-exempt bonds, due 2040 | Recourse Debt
Debt and Capital Leases
Interest rate, stated rate	6.00%	[1]
Indian River Power LLC, tax-exempt bonds, due 2045 | Recourse Debt
Debt and Capital Leases
Interest rate, stated rate	5.38%	[1]
Tax-exempt Bonds [Member] | Recourse Debt
Debt and Capital Leases
Long-term Debt	434		406
Dunkirk Power LLC, tax-exempt bonds, due 2042 | Recourse Debt
Debt and Capital Leases
Interest rate, stated rate	5.88%	[1]
Fort Bend County, tax-exempt bonds, due 2038 and 2042 | Recourse Debt
Debt and Capital Leases
Interest rate, stated rate	4.13%	[1]
GenOn Senior Notes [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	2,121		2,133
GenOn Senior Notes Due in 2017 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	7.88%	[1]
GenOn senior notes, due 2018 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	9.50%	[1]
GenOn senior notes, due 2020 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	9.88%	[1]
GenOn Americas Generation Senior Notes [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	926		929
GenOn Americas Generation Senior Notes Due in 2021 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	8.50%	[1]
GenOn Americas Generation senior notes, due in 2031 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	9.13%	[1]
GenOn Other [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	60		60
Genon [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	3,107		3,122
5.375% Senior Notes due in 2024 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	500		500
Interest rate, stated rate	5.38%	[1]
Revolving Credit Facility [Member]
Debt and Capital Leases
Interest rate, variable basis	1 - month LIBOR
Revolving Credit Facility [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	195		0
NRG West Holdings LLC, term loan, due 2023
Debt and Capital Leases
Interest rate, variable basis	1 - month LIBOR
NRG West Holdings LLC, term loan, due 2023 | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	484		506
GenOn Marsh Landing term loans, due 2017 and 2023
Debt and Capital Leases
Interest rate, variable basis	1 - month LIBOR
GenOn Marsh Landing term loans, due 2017 and 2023 | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	457		464
Alta Wind I - V Lease financing arrangement [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	1,036		1,036
Alta Wind I [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	7.02%	[1]
Alta Wind II [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	5.70%	[1]
Alta Wind III [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	6.07%	[1]
Alta Wind IV [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	5.94%	[1]
Alta Wind V [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	6.07%	[1]
Alta Wind X [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	300		300
Alta Wind XI [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	191		191
NRG Solar Alpine LLC, due 2022 | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	162		163
NRG Energy Center Minneapolis LLC, senior secured notes, due 2013, 2017, and 2025 | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	119		121
NRG Energy Center Minneapolis LLC Senior Secured Notes, due 2017 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, range, minimum	7.12%	[1]
Interest rate, range, maximum	7.25%	[1]
NRG Energy Center Minneapolis LLC Senior Secured Notes, due 2025 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, stated rate	5.95%	[1]
NRG Yield - Other [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	487		489
NRG Yield, Inc. | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	4,937		4,787
Interest rate, stated rate	3.50%	[1]
Ivanpah Financing, due 2014 and 2038 | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	1,179		1,187
Interest rate, range, minimum	2.29%	[1]
Interest rate, range, maximum	4.26%	[1]
Agua Caliente Solar LLC, due 2037 | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	907		898
Interest rate, range, minimum	2.40%	[1]
Interest rate, range, maximum	3.63%	[1]
CVSR - High Plains Ranch II LLC, due 2037 | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	802		815
Interest rate, range, minimum	2.34%	[1]
Interest rate, range, maximum	3.78%	[1]
Walnut Creek Energy, LLC, due in 2023 [Member]
Debt and Capital Leases
Interest rate, variable basis	1 - month LIBOR
Walnut Creek Energy, LLC, due in 2023 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	384		391
Interest rate, variable basis	LIBOR	[1]
Tapestry Wind LLC due in 2021 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	188		192
Interest rate, variable basis	LIBOR	[1]
Laredo Ridge Wind, LLC, due in 2026 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	107		108
Interest rate, variable basis	LIBOR	[1]
Viento Funding II, Inc., due in 2023 [Member]
Debt and Capital Leases
Interest rate, variable basis	6 month LIBOR
Viento Funding II, Inc., due in 2023 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	196		196
Interest rate, variable basis	LIBOR	[1]
NRG Peaker Finance Co. LLC Bonds Due 2019 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	101		100
Interest rate, variable basis	LIBOR	[1]
Cedro Hill Wind LLC, due in 2025 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	108		111
Interest rate, variable basis	LIBOR	[1]
Other (Non-recourse debt) | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	349		350
NRG Energy [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt	3,642		3,657
Chalk Point capital lease, due 2015
Debt and Capital Leases
Chalk Point capital lease, due 2015	3		5
Interest rate, Chalk Point capital lease	8.19%	[1]
Other (Capital leases)
Debt and Capital Leases
Chalk Point capital lease, due 2015	$3		$3
London Interbank Offered Rate (LIBOR) [Member] | Term loan facility, due 2018 | Recourse Debt
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, basis spread on variable rate	2.00%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, basis spread on variable rate	2.25%	[1]
London Interbank Offered Rate (LIBOR) [Member] | NRG West Holdings LLC, term loan, due 2023 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, range, minimum	2.25%	[1]
Interest rate, range, maximum	2.88%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Marsh Landing Term Loan Due 2017 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, basis spread on variable rate	1.75%	[1]
London Interbank Offered Rate (LIBOR) [Member] | GenOn Marsh Landing term loan, due 2023 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, basis spread on variable rate	1.88%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Alta Wind X [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, basis spread on variable rate	2.00%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Alta Wind XI [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, basis spread on variable rate	2.00%	[1]
London Interbank Offered Rate (LIBOR) [Member] | NRG Solar Alpine LLC, due 2022 | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, variable basis	LIBOR	[1]
Interest rate, range, minimum	1.75%	[1]
Interest rate, range, maximum	0.00%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Walnut Creek Energy, LLC, due in 2023 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, basis spread on variable rate	1.63%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Tapestry Wind LLC due in 2021 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, basis spread on variable rate	1.63%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Laredo Ridge Wind, LLC, due in 2026 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, basis spread on variable rate	1.88%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Viento Funding II, Inc., due in 2023 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, basis spread on variable rate	2.75%	[1]
London Interbank Offered Rate (LIBOR) [Member] | NRG Peaker Finance Co. LLC Bonds Due 2019 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, basis spread on variable rate	1.07%	[1]
London Interbank Offered Rate (LIBOR) [Member] | Cedro Hill Wind LLC, due in 2025 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Interest rate, basis spread on variable rate	3.13%	[1]
[1]	As of March 31, 2015, L+ equals 3 month LIBOR plus x%, with the exception of the Viento Funding II term loan which is 6 month LIBOR plus x% and the NRG West Holdings LLC term loan, NRG Marsh Landing term loan, Walnut Creek term loan, and NRG Yield Operating LLC Revolving Credit facility which are 1 month LIBOR plus x%.

Debt_and_Capital_Leases_Debt_a1

Debt and Capital Leases Debt and Capital Leases (Details 2 - Issuances) (Recourse Debt, USD $)	0 Months Ended
In Billions, unless otherwise specified	Jan. 27, 2014	Mar. 31, 2015
Senior Notes 2024 [Member]
Debt and Capital Leases
Debt Instrument, Interest Rate, Stated Percentage		6.25%	[1]
Senior Notes Due In 2022 [Member]
Debt and Capital Leases
Proceeds from Issuance of Senior Long-term Debt	$1.10
Debt Instrument, Interest Rate, Stated Percentage	6.25%	6.25%	[1]
Senior Notes Due In 2019 7625 [Member]
Debt and Capital Leases
Debt Instrument, Interest Rate, Stated Percentage		7.63%
Senior Notes Due In 2019 850 [Member]
Debt and Capital Leases
Debt Instrument, Interest Rate, Stated Percentage		8.50%
[1]	As of March 31, 2015, L+ equals 3 month LIBOR plus x%, with the exception of the Viento Funding II term loan which is 6 month LIBOR plus x% and the NRG West Holdings LLC term loan, NRG Marsh Landing term loan, Walnut Creek term loan, and NRG Yield Operating LLC Revolving Credit facility which are 1 month LIBOR plus x%.

Debt_and_Capital_Leases_Debt_a2

Debt and Capital Leases Debt and Capital Leases (Details 3 - Redemptions) (USD $)	3 Months Ended		0 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Feb. 10, 2014	Dec. 31, 2014	Apr. 01, 2014	Aug. 12, 2014
Debt and Capital Leases
Gains (Losses) on Extinguishment of Debt	$0	($41)
Long-term Debt	20,509			20,366
EME [Member]
Debt and Capital Leases
Long-term Debt					1,200
Alta Wind Portfolio [Member]
Debt and Capital Leases
Long-term Debt						1,600
Recourse Debt
Debt and Capital Leases
Gains (Losses) on Extinguishment of Debt		-33
Long-term Debt	8,823			8,800
Recourse Debt | Senior Notes Due In 2019 850 [Member]
Debt and Capital Leases
Repayments of Senior Debt			308
Debt Instrument, Interest Rate, Stated Percentage	8.50%
Debt Instrument, Redemption Price, Percentage			106.99%
Recourse Debt | Senior Notes Due In 2019 7625 [Member]
Debt and Capital Leases
Repayments of Senior Debt			$91
Debt Instrument, Interest Rate, Stated Percentage	7.63%
Debt Instrument, Redemption Price, Percentage			105.50%

Debt_and_Capital_Leases_Debt_a3

Debt and Capital Leases Debt and Capital Leases (Details 4 - Yield and Peakers) (USD $)	3 Months Ended	2 Months Ended
	Mar. 31, 2014	Apr. 02, 2015	Mar. 31, 2015		Dec. 31, 2014	Jan. 02, 2015	Jun. 30, 2014	Apr. 25, 2014	Feb. 21, 2014
Debt and Capital Leases
Convertible Debt	$345,000,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt	23,000,000
Long-term Debt			20,509,000,000		20,366,000,000
Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt			11,686,000,000		11,566,000,000
5.375% Senior Notes due in 2024 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Debt Instrument, Interest Rate, Stated Percentage			5.38%	[1]
Long-term Debt			500,000,000		500,000,000
Convertible Debt [Member]
Debt and Capital Leases
Debt Instrument, Interest Rate, Stated Percentage	3.50%
Debt Instrument, Convertible, Conversion Price	$46.55
Debt Instrument, Convertible, Conversion Ratio	21.4822
Debt Instrument, Face Amount	1,000
NRG Yield Revolving Credit Facility [Member]
Debt and Capital Leases
Repayments of Debt		15,000,000
Line of Credit Facility, Maximum Borrowing Capacity							60,000,000	450,000,000
Long-term Debt						210,000,000
Letters of Credit, Issued Amount			36,000,000
NRG Peaker Finance Co. LLC Bonds Due 2019 [Member]
Debt and Capital Leases
Debt Instrument, Repurchased Face Amount									30,000,000
Debt Instrument, Repurchase Amount									35,000,000
NRG Peaker Finance Co. LLC Bonds Due 2019 [Member] | Non Recourse Debt [Member]
Debt and Capital Leases
Long-term Debt			$101,000,000		$100,000,000
[1]	As of March 31, 2015, L+ equals 3 month LIBOR plus x%, with the exception of the Viento Funding II term loan which is 6 month LIBOR plus x% and the NRG West Holdings LLC term loan, NRG Marsh Landing term loan, Walnut Creek term loan, and NRG Yield Operating LLC Revolving Credit facility which are 1 month LIBOR plus x%.

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified	MW
Investments Accounted for by the Equity Method
Generation Capacity (in MW)	51,000
Equity investments in affiliates	$772	$771
Net assets less noncontrolling interests	25
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	112
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	81
Capistrano Wind [Member]
Investments Accounted for by the Equity Method
Generation Capacity (in MW)	411
Percentage of Ownership	100.00%
Power Generation Plants, Number	5
Cash Available for Distributions	100.00%
Current assets	28
Net property, plant and equipment	578
Other long-term assets	137
Total assets	743
Current liabilities	36
Long-term debt	180
Other long-term liabilities	154
Total liabilities	370
Noncontrolling interests	$348

Changes_in_Capital_Structure_D

Changes in Capital Structure (Details)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Common stock authorized (in shares)
Common stock, shares authorized	500,000,000	500,000,000
Shares issued, balance at the beginning of the year		415,506,176
Shares issued, balance at the end of the year	416,682,662	415,506,176
Treasury shares, balance at the beginning of the year		-78,843,552
Treasury shares, balance at the beginning of the year	-81,865,411	-78,843,552
Shares outstanding, balance at the end of the year	334,817,251	336,662,624
Common Stock, Capital Shares Reserved for Employee Stock Purchase Plan	1,435,427
Long Term Incentive Plan [Member]
Common stock authorized (in shares)
Stock Issued During Period, Shares, New Issues	1,176,486
Treasury Stock, Shares, Acquired	0
Shares outstanding, balance at the end of the year	1,176,486
Employee Stock [Member]
Common stock authorized (in shares)
Stock Issued During Period, Shares, New Issues	0
Treasury Stock, Shares, Acquired	124,625
Shares outstanding, balance at the end of the year	124,625
Capital Allocation Plan [Member]
Common stock authorized (in shares)
Stock Issued During Period, Shares, New Issues	0
Treasury Stock, Shares, Acquired	-3,146,484
Shares outstanding, balance at the end of the year	-3,146,484

Changes_in_Capital_Structure_D1

Changes in Capital Structure (Details 2) (USD $)

1 Months Ended

3 Months Ended

5 Months Ended

1 Months Ended

3 Months Ended

12 Months Ended

In Millions, except Share data, unless otherwise specified

Mar. 31, 2015

Feb. 28, 2015

Jan. 31, 2015

Mar. 31, 2015

Dec. 31, 2014

Mar. 31, 2014

Apr. 30, 2015

Apr. 30, 2015

Jun. 30, 2015

Dec. 31, 2015

Mar. 16, 2015

Dec. 09, 2014

Employee Stock Purchase Plan and 2013 Capital Allocation Plan

Payments for Commissions

$0.02

Dividend paid

$0.15

$0.12

Stock Repurchase Program, Authorized Amount

$200

$200

$100

$100

Stock Repurchased During Period, Shares

921,654

468,854

1,755,976

3,146,484

1,624,360

6,099,173

Stock Repurchased During Period, Value

23

[1]

12

[1]

44

[1]

79

[1]

44

[1]

156

[1]

Treasury Stock Acquired, Average Cost Per Share

$24.92

[1]

$25.46

[1]

$25.19

[1]

$26.95

[1]

Subsequent Event [Member]

Employee Stock Purchase Plan and 2013 Capital Allocation Plan

Dividends Payable, Date Declared

20-Apr-15

Dividend declared

$0.15

Dividends Payable, Date to be Paid

15-May-15

Stock Repurchased During Period, Shares

1,328,329

Stock Repurchased During Period, Value

$33

[1]

Treasury Stock Acquired, Average Cost Per Share

$24.47

[1]

Scenario, Plan [Member] | Subsequent Event [Member]

Employee Stock Purchase Plan and 2013 Capital Allocation Plan

NRG's annual common stock dividend, proposed amount for 2013

$0.58

[1]

The average price paid per share and amounts paid for shares purchased excludes the commissions of $0.015 per share paid in connection with the share repurchase.

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Numerator:
Net Loss Attributable to NRG Energy, Inc.	($120)		($56)
Dividends for preferred shares	5		2
Loss available for common stockholders	($125)		($58)
Denominator:
Weighted average number of common shares outstanding - basic and diluted	336		324
Basic earnings per share:
Loss per weighted average common share — basic and diluted	($0.37)		($0.18)
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of diluted earnings per share, amount	23		24
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	2.82%		3.63%		2.82%
Equity compensation plans
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of diluted earnings per share, amount	7		8
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	[1]	16	[1]
[1]	As of March 31, 2014, the redeemable perpetual preferred stock had an interest rate of 3.625%.

Segment_Reporting_Details

Segment Reporting (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Segment Reporting Information
Operating revenues	$3,826	[1]	$3,486	[2]
Depreciation and amortization	395		335
Equity in earnings/(losses) of unconsolidated affiliates	-3		7
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	-209		-98
Net Loss Attributable to NRG Energy, Inc.	-120		-56
Total Assets	40,330				40,665
Inter-Segment Sales	279		141
Loss on debt extinguishment	0		-41
NRG Business [Member]
Segment Reporting Information
Operating revenues	2,506	[1]	2,346	[2]
Depreciation and amortization	233		225
Equity in earnings/(losses) of unconsolidated affiliates	-4		5
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	29		-6
Net Loss Attributable to NRG Energy, Inc.	29		-6
Total Assets	28,744
Inter-Segment Sales	246		113
Loss on debt extinguishment			0
NRG Yield
Segment Reporting Information
Operating revenues	180	[1]	140	[2]
Depreciation and amortization	54		24
Equity in earnings/(losses) of unconsolidated affiliates	1		1
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	-20		29
Net Loss Attributable to NRG Energy, Inc.	-11		22
Total Assets	6,595
Inter-Segment Sales	0		0
Loss on debt extinguishment			0
Corporate
Segment Reporting Information
Operating revenues	-7	[1]	4	[2],[3]
Depreciation and amortization	7		6	[3]
Equity in earnings/(losses) of unconsolidated affiliates	-1		2	[3]
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	-217		-239	[3]
Net Loss Attributable to NRG Energy, Inc.	-142		-209	[3]
Total Assets	31,493
Inter-Segment Sales	33		26
Loss on debt extinguishment			-40
Elimination
Segment Reporting Information
Operating revenues	-279	[1]	-141	[2]
Depreciation and amortization	0		0
Equity in earnings/(losses) of unconsolidated affiliates	1		2
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	1		0
Net Loss Attributable to NRG Energy, Inc.	-5		2
Total Assets	-40,105
Inter-Segment Sales	0		0
Loss on debt extinguishment			0
NRG Home Retail [Member]
Segment Reporting Information
Operating revenues	1,311	[1]	1,082	[2]
Depreciation and amortization	30		30
Equity in earnings/(losses) of unconsolidated affiliates	0		0
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	104		185
Net Loss Attributable to NRG Energy, Inc.	104		185
Total Assets	6,270
Inter-Segment Sales	0		2
Loss on debt extinguishment			0
Home Solar [Member]
Segment Reporting Information
Operating revenues	5	[1]	2	[2]
Depreciation and amortization	6		1
Equity in earnings/(losses) of unconsolidated affiliates	0		0
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	-45		-2
Net Loss Attributable to NRG Energy, Inc.	-45		-2
Total Assets	178
Inter-Segment Sales	0		0
Loss on debt extinguishment			0
NRG Renew [Member]
Segment Reporting Information
Operating revenues	110	[1]	53	[2],[3]
Depreciation and amortization	65		49	[3]
Equity in earnings/(losses) of unconsolidated affiliates	0		-3	[3]
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	-61		-65	[3]
Net Loss Attributable to NRG Energy, Inc.	-50		-48	[3]
Total Assets	7,155
Inter-Segment Sales	0		0
Loss on debt extinguishment			($1)
[1]	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:$246 $— $— $— $— $33 $— $279
[2]	(b) Operating revenues include inter-segment sales and net derivative gains and losses of:$113 $2 $— $— $— $26 $— $141
[3]	(c) Includes loss on debt extinguishment of:$— $— $— $(1) $— $(40) $— $(41)

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Valuation Allowance [Line Items]
Non-current tax liability for uncertain tax benefits	$55
Effective Tax Rate
Loss before income taxes	-209	-98
Income tax benefit	-73	-31
Effective tax rate (as a percent)	34.90%	31.60%
Statutory tax rate (as a percent)	35.00%	35.00%
Uncertain Tax Benefits
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$6

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	1 Months Ended	3 Months Ended
	Jun. 30, 2013	Sep. 30, 2010
Notice of Intent to File Citizens Suit
Loss Contingencies
Civil Penalties	$100,000
Midwest Generation New Source Review [Member]
Loss Contingencies
Civil Penalties		$37,500

Regulatory_Matters_Details

Regulatory Matters (Details) (Genon [Member], USD $)	Dec. 20, 2013
In Millions, unless otherwise specified
Genon [Member]
Regulatory Matters [Line Items]
Regulatory payments sought	$22

Environmental_Matters_Details

Environmental Matters (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Millions, unless otherwise specified
Environmental capital expenditures [Line Items]
Environmental Capital Expenditures, Estimated	$614
Genon [Member]
Environmental capital expenditures [Line Items]
Environmental Capital Expenditures, Estimated	57
Midwest Generation [Member]
Environmental capital expenditures [Line Items]
Environmental Capital Expenditures, Estimated	440
EME [Member]
Environmental capital expenditures [Line Items]
Environmental Capital Expenditures, Estimated Total		$350

Condensed_Consolidating_Financ2

Condensed Consolidating Financial Information (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Debt Instrument
Long-term Debt	$20,509	$20,366
Recourse Debt
Debt Instrument
Long-term Debt	8,823	8,800
Senior Notes [Member] | Recourse Debt
Debt Instrument
Long-term Debt	$6,400

Condensed_Consolidating_Financ3

Condensed Consolidating Financial Information (Details 2) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Operating Revenues
Total operating revenues	$3,826	[1]	$3,486	[2]
Operating Costs and Expenses
Cost of operations	3,062		2,737
Depreciation and amortization	395		335
Selling, general and administrative	263		222
Acquisition-related transaction and integration costs	10		12
Development activity expenses	34		19
Total operating costs and expenses	3,764		3,325
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	14
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			19
Gain (Loss) on Disposition of Property Plant Equipment	14		19
Gain on postretirement benefits curtailment and sale of assets	14		19
Operating Income (Loss)	76		180
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	0		0
Equity in (loss)/earnings of unconsolidated affiliates	-3		7
Other income, net	19		11
Loss on debt extinguishment	0		-41
Interest expense	-301		-255
Total other expense	-285		-278
Loss before income taxes	-209		-98
Income tax expense/(benefit)	-73		-31
Net Loss	-136		-67
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	-16		-11
Net (Loss)/Income Attributable to NRG Energy, Inc.	-120		-56
Other Comprehensive Income/(Loss), net of tax
Unrealized (loss)/gain on derivatives, net	-12		-9
Foreign currency translation adjustments, net	-11		6
Available-for-sale securities, net	-1		6
Defined benefit plan, net	7		2
Other comprehensive (loss)/income	-17		5
Comprehensive Income/(Loss)	-153		-62
Comprehensive loss attributable to noncontrolling interest	-29		-15
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	-124		-47
Dividends for preferred shares	-5		-2
Comprehensive (Loss)/Income Available for Common Stockholders	-129		-49
Guarantor Subsidiaries
Operating Revenues
Total operating revenues	2,563		2,279
Operating Costs and Expenses
Cost of operations	2,104		1,797
Depreciation and amortization	204		198
Selling, general and administrative	102		101
Acquisition-related transaction and integration costs	0		0
Development activity expenses	0		0
Total operating costs and expenses	2,410		2,096
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			0
Operating Income (Loss)	153		183
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	-13		49
Equity in (loss)/earnings of unconsolidated affiliates	0		4
Other income, net	1		1
Loss on debt extinguishment	0		0
Interest expense	-4		-6
Total other expense	-16		48
Loss before income taxes	137		231
Income tax expense/(benefit)	54		63
Net Loss	83		168
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	0		0
Net (Loss)/Income Attributable to NRG Energy, Inc.	83		168
Other Comprehensive Income/(Loss), net of tax
Unrealized (loss)/gain on derivatives, net	-7		6
Foreign currency translation adjustments, net	0		0
Available-for-sale securities, net	0		0
Defined benefit plan, net	3		-2
Other comprehensive (loss)/income	-10		8
Comprehensive Income/(Loss)	73		176
Comprehensive loss attributable to noncontrolling interest	0		0
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	73		176
Dividends for preferred shares	0		0
Comprehensive (Loss)/Income Available for Common Stockholders	73		176
Non-Guarantor Subsidiaries
Operating Revenues
Total operating revenues	1,303		1,251
Operating Costs and Expenses
Cost of operations	995		974
Depreciation and amortization	186		134
Selling, general and administrative	101		57
Acquisition-related transaction and integration costs	2		1
Development activity expenses	15		10
Total operating costs and expenses	1,299		1,176
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	14
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			19
Operating Income (Loss)	18		94
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	-8		-6
Equity in (loss)/earnings of unconsolidated affiliates	-4		1
Other income, net	17		4
Loss on debt extinguishment	0		-9
Interest expense	-158		-107
Total other expense	-153		-117
Loss before income taxes	-135		-23
Income tax expense/(benefit)	-60		-10
Net Loss	-75		-13
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	-21		-3
Net (Loss)/Income Attributable to NRG Energy, Inc.	-54		-10
Other Comprehensive Income/(Loss), net of tax
Unrealized (loss)/gain on derivatives, net	11		-6
Foreign currency translation adjustments, net	-9		6
Available-for-sale securities, net	-1		0
Defined benefit plan, net	1		0
Other comprehensive (loss)/income	0		0
Comprehensive Income/(Loss)	-75		-13
Comprehensive loss attributable to noncontrolling interest	-34		-5
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	-41		-8
Dividends for preferred shares	0		0
Comprehensive (Loss)/Income Available for Common Stockholders	-41		-8
NRG Energy, Inc.
Operating Revenues
Total operating revenues	0		0
Operating Costs and Expenses
Cost of operations	12		-4
Depreciation and amortization	5		3
Selling, general and administrative	60		64
Acquisition-related transaction and integration costs	8		11
Development activity expenses	19		9
Total operating costs and expenses	104		83
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			0
Operating Income (Loss)	-104		-83
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	50		115
Equity in (loss)/earnings of unconsolidated affiliates	-1		0
Other income, net	1		7
Loss on debt extinguishment	0		-32
Interest expense	-139		-143
Total other expense	-89		-53
Loss before income taxes	-193		-136
Income tax expense/(benefit)	-67		-84
Net Loss	-126		-52
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	-6		4
Net (Loss)/Income Attributable to NRG Energy, Inc.	-120		-56
Other Comprehensive Income/(Loss), net of tax
Unrealized (loss)/gain on derivatives, net	-16		5
Foreign currency translation adjustments, net	-2		0
Available-for-sale securities, net	0		4
Defined benefit plan, net	-11		0
Other comprehensive (loss)/income	-7		9
Comprehensive Income/(Loss)	-133		-43
Comprehensive loss attributable to noncontrolling interest	-6		4
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	-127		-47
Dividends for preferred shares	-5		-2
Comprehensive (Loss)/Income Available for Common Stockholders	-132		-49
Eliminations
Operating Revenues
Total operating revenues	-40	[3]	-44	[4]
Operating Costs and Expenses
Cost of operations	-49	[3]	-30	[4]
Depreciation and amortization	0	[3]	0	[4]
Selling, general and administrative	0	[3]	0	[4]
Acquisition-related transaction and integration costs	0	[3]	0	[4]
Development activity expenses	0	[3]	0	[4]
Total operating costs and expenses	-49	[3]	-30	[4]
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal			0	[4]
Operating Income (Loss)	9	[3]	-14	[4]
Other Income/(Expense)
Equity in earnings/(losses) of consolidated subsidiaries	-29	[3]	-158	[4]
Equity in (loss)/earnings of unconsolidated affiliates	2	[3]	2	[4]
Other income, net	0	[3]	-1	[4]
Loss on debt extinguishment	0	[3]	0	[4]
Interest expense	0	[3]	1	[4]
Total other expense	-27	[3]	-156	[4]
Loss before income taxes	-18	[3]	-170	[4]
Income tax expense/(benefit)	0	[3]	0	[4]
Net Loss	-18	[3]	-170	[4]
Less: Net loss attributable to noncontrolling interest and redeemable noncontrolling interests	11	[3]	-12	[4]
Net (Loss)/Income Attributable to NRG Energy, Inc.	-29	[3]	-158	[4]
Other Comprehensive Income/(Loss), net of tax
Unrealized (loss)/gain on derivatives, net	0	[4]	-14	[3]
Foreign currency translation adjustments, net	0	[4]	0	[3]
Available-for-sale securities, net	0	[4]	2	[3]
Defined benefit plan, net	0	[4]	0	[3]
Other comprehensive (loss)/income	0	[4]	-12	[3]
Comprehensive Income/(Loss)	-18	[4]	-182	[3]
Comprehensive loss attributable to noncontrolling interest	11	[4]	-14	[3]
Comprehensive Income/(Loss) Attributable to NRG Energy, Inc.	-29	[4]	-168	[3]
Dividends for preferred shares	0	[4]	0	[3]
Comprehensive (Loss)/Income Available for Common Stockholders	($29)	[4]	($168)	[3]
[1]	(a) Operating revenues include inter-segment sales and net derivative gains and losses of:$246 $— $— $— $— $33 $— $279
[2]	(b) Operating revenues include inter-segment sales and net derivative gains and losses of:$113 $2 $— $— $— $26 $— $141
[3]	All significant intercompany transactions have been eliminated in consolidation.
[4]	(a)All significant intercompany transactions have been eliminated in consolidation.

Condensed_Consolidating_Financ4

Condensed Consolidating Financial Information (Details 3) (USD $)	Mar. 31, 2015		Dec. 31, 2014		Mar. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Current Assets
Cash and cash equivalents	$2,164		$2,116		$3,187		$2,254
Funds deposited by counterparties	68		72
Restricted cash	443		457
Accounts receivable-trade, net	1,179		1,322
Inventory	1,109		1,247
Derivative instruments	2,029		2,425
Cash collateral paid in support of energy risk management activities	400		187
Due from Affiliate, Current	7		9
Deferred income taxes	188		174
Renewable energy grant receivable, net	68		135
Prepayments and other current assets	467		612
Total current assets	8,122		8,582
Net property, plant and equipment	22,276		22,367
Other Assets
Investment in subsidiaries	0		0
Equity investments in affiliates	772		771
Capital leases and notes receivable, less current portion	67		72
Goodwill	2,520		2,574
Intangible assets, net	2,491		2,567
Nuclear decommissioning trust fund	586		585
Derivative instruments	591		480
Deferred income taxes	1,484		1,406
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent	17		17
Other non-current assets	1,404		1,244
Total other assets	9,932		9,716
Total Assets	40,330		40,665
Current Liabilities
Current portion of long-term debt and capital leases	465		474
Accounts payable	1,045		1,060
Accounts payable — affiliate	0		0
Derivative instruments	1,884		2,054
Cash collateral received in support of energy risk management activities	68		72
Deferred Tax Liabilities, Net, Current			0
Accrued expenses and other current liabilities	1,047		1,199
Total current liabilities	4,509		4,859
Other Liabilities
Long-term debt and capital leases	20,050		19,900
Nuclear decommissioning reserve	314		310
Nuclear decommissioning reserve	328		333
Deferred income taxes	20		21
Derivative instruments	650		438
Out-of-market contracts, net of accumulated amortization of $585 and $562	1,221		1,244
Other non-current liabilities	1,549		1,574
Total non-current liabilities	24,132		23,820
Total Liabilities	28,641		28,679
3.625% convertible perpetual preferred stock	293		291
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount	19		19
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	2.82%		2.82%		3.63%
Total Stockholders' Equity	11,377		11,676
Total Liabilities and Stockholders’ Equity	40,330		40,665
Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	13		18		22		56
Funds deposited by counterparties	39		9
Restricted cash	14		5
Accounts receivable-trade, net	936		924
Inventory	505		537
Derivative instruments	1,480		1,657
Cash collateral paid in support of energy risk management activities	246		114
Due from Affiliate, Current	8,656		7,449
Deferred income taxes	0
Renewable energy grant receivable, net	0		0
Prepayments and other current assets	148		94
Total current assets	12,037		10,807
Net property, plant and equipment	8,260		8,344
Other Assets
Investment in subsidiaries	422		140
Equity investments in affiliates	-18		-18
Capital leases and notes receivable, less current portion	0		1
Goodwill	2,072		1,921
Intangible assets, net	859		765
Nuclear decommissioning trust fund	586		585
Derivative instruments	318		242
Deferred income taxes	-61		-247
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent	0		0
Other non-current assets	112		113
Total other assets	4,290		3,502
Total Assets	24,587		22,653
Current Liabilities
Current portion of long-term debt and capital leases	1		1
Accounts payable	645		598
Accounts payable — affiliate	2,336		1,588
Derivative instruments	1,439		1,532
Cash collateral received in support of energy risk management activities	39		9
Deferred Tax Liabilities, Net, Current			7
Accrued expenses and other current liabilities	233		283
Total current liabilities	4,693		4,018
Other Liabilities
Long-term debt and capital leases	308		307
Nuclear decommissioning reserve	314		310
Nuclear decommissioning reserve	328		333
Deferred income taxes	1,284		1,036
Derivative instruments	369		248
Out-of-market contracts, net of accumulated amortization of $585 and $562	107		111
Other non-current liabilities	490		465
Total non-current liabilities	3,200		2,810
Total Liabilities	7,893		6,828
3.625% convertible perpetual preferred stock	0		0
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount	0		0
Total Stockholders' Equity	16,694		15,825
Total Liabilities and Stockholders’ Equity	24,587		22,653
Non-Guarantor Subsidiaries
Current Assets
Cash and cash equivalents	1,378		1,455		1,459		870
Funds deposited by counterparties	29		63
Restricted cash	427		451
Accounts receivable-trade, net	240		392
Inventory	604		710
Derivative instruments	938		1,209
Cash collateral paid in support of energy risk management activities	154		73
Due from Affiliate, Current	2,103		1,988
Deferred income taxes	93
Renewable energy grant receivable, net	68		134
Prepayments and other current assets	319		175
Total current assets	6,353		6,650
Net property, plant and equipment	13,847		13,877
Other Assets
Investment in subsidiaries	2,542		2,293
Equity investments in affiliates	841		891
Capital leases and notes receivable, less current portion	58		60
Goodwill	448		653
Intangible assets, net	1,637		1,806
Nuclear decommissioning trust fund	0		0
Derivative instruments	321		288
Deferred income taxes	652		816
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent	17		17
Other non-current assets	681		623
Total other assets	7,197		7,447
Total Assets	27,397		27,974
Current Liabilities
Current portion of long-term debt and capital leases	445		444
Accounts payable	358		416
Accounts payable — affiliate	2,853		2,447
Derivative instruments	834		963
Cash collateral received in support of energy risk management activities	29		63
Deferred Tax Liabilities, Net, Current			0
Accrued expenses and other current liabilities	496		498
Total current liabilities	5,015		4,831
Other Liabilities
Long-term debt and capital leases	11,456		11,226
Nuclear decommissioning reserve	0		0
Nuclear decommissioning reserve	0		0
Deferred income taxes	-1,039		-1,012
Derivative instruments	330		241
Out-of-market contracts, net of accumulated amortization of $585 and $562	1,114		1,133
Other non-current liabilities	767		795
Total non-current liabilities	12,628		12,383
Total Liabilities	17,643		17,214
3.625% convertible perpetual preferred stock	0		0
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount	19		19
Total Stockholders' Equity	9,735		10,741
Total Liabilities and Stockholders’ Equity	27,397		27,974
NRG Energy, Inc.
Current Assets
Cash and cash equivalents	773		643		1,706		1,328
Funds deposited by counterparties	0		0
Restricted cash	2		1
Accounts receivable-trade, net	3		6
Inventory	0		0
Derivative instruments	0		0
Cash collateral paid in support of energy risk management activities	0		0
Due from Affiliate, Current	-5,750		-5,991
Deferred income taxes	95
Renewable energy grant receivable, net	0		1
Prepayments and other current assets	0		343
Total current assets	-4,877		-4,997
Net property, plant and equipment	194		171
Other Assets
Investment in subsidiaries	21,907		23,410
Equity investments in affiliates	39		0
Capital leases and notes receivable, less current portion	221		109
Goodwill	0		0
Intangible assets, net	1		2
Nuclear decommissioning trust fund	0		0
Derivative instruments	1		1
Deferred income taxes	893		837
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent	0		0
Other non-current assets	611		508
Total other assets	23,673		24,867
Total Assets	18,990		20,041
Current Liabilities
Current portion of long-term debt and capital leases	231		127
Accounts payable	42		46
Accounts payable — affiliate	-576		-598
Derivative instruments	0		0
Cash collateral received in support of energy risk management activities	0		0
Deferred Tax Liabilities, Net, Current			-7
Accrued expenses and other current liabilities	318		418
Total current liabilities	15		-14
Other Liabilities
Long-term debt and capital leases	8,286		8,367
Nuclear decommissioning reserve	0		0
Nuclear decommissioning reserve	0		0
Deferred income taxes	-225		-3
Derivative instruments	0		0
Out-of-market contracts, net of accumulated amortization of $585 and $562	0		0
Other non-current liabilities	292		314
Total non-current liabilities	8,353		8,678
Total Liabilities	8,368		8,664
3.625% convertible perpetual preferred stock	293		291
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount	0		0
3.625% convertible perpetual preferred stock, interest rate (as a percentage)	2.82%		2.82%
Total Stockholders' Equity	10,329		11,086
Total Liabilities and Stockholders’ Equity	18,990		20,041
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	-389	[1]	-441	[1]
Cash collateral paid in support of energy risk management activities	0	[1]	0	[1]
Due from Affiliate, Current	-5,002	[1]	-3,437	[1]
Deferred income taxes	0	[1]
Renewable energy grant receivable, net	0	[1]	0	[1]
Prepayments and other current assets	0	[1]	0	[1]
Total current assets	-5,391	[1]	-3,878	[1]
Net property, plant and equipment	-25	[1]	-25	[1]
Other Assets
Investment in subsidiaries	-24,871	[1]	-25,843	[1]
Equity investments in affiliates	-90	[1]	-102	[1]
Capital leases and notes receivable, less current portion	-212	[1]	-98	[1]
Goodwill	0	[1]	0	[1]
Intangible assets, net	-6	[1]	-6	[1]
Nuclear decommissioning trust fund	0	[1]	0	[1]
Derivative instruments	-49	[1]	-51	[1]
Deferred income taxes	0	[1]	0	[1]
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent	0	[1]	0	[1]
Other non-current assets	0	[1]	0	[1]
Total other assets	-25,228	[1]	-26,100	[1]
Total Assets	-30,644	[1]	-30,003	[1]
Current Liabilities
Current portion of long-term debt and capital leases	-212	[1]	-98	[1]
Accounts payable	0	[1]	0	[1]
Accounts payable — affiliate	-4,613	[1]	-3,437	[1]
Derivative instruments	-389	[1]	-441	[1]
Cash collateral received in support of energy risk management activities	0	[1]	0	[1]
Deferred Tax Liabilities, Net, Current			0	[1]
Accrued expenses and other current liabilities	0	[1]	0	[1]
Total current liabilities	-5,214	[1]	-3,976	[1]
Other Liabilities
Long-term debt and capital leases	0	[1]	0	[1]
Nuclear decommissioning reserve	0	[1]	0	[1]
Nuclear decommissioning reserve	0	[1]	0	[1]
Deferred income taxes	0	[1]	0	[1]
Derivative instruments	-49	[1]	-51	[1]
Out-of-market contracts, net of accumulated amortization of $585 and $562	0	[1]	0	[1]
Other non-current liabilities	0	[1]	0	[1]
Total non-current liabilities	-49	[1]	-51	[1]
Total Liabilities	-5,263	[1]	-4,027	[1]
3.625% convertible perpetual preferred stock	0	[1]	0	[1]
Redeemable Noncontrolling Interest, Equity, Other, Carrying Amount	0	[1]	0	[1]
Total Stockholders' Equity	-25,381	[1]	-25,976	[1]
Total Liabilities and Stockholders’ Equity	($30,644)	[1]	($30,003)	[1]
[1]	All significant intercompany transactions have been eliminated in consolidation.

Condensed_Consolidating_Financ5

Condensed Consolidating Financial Information (Details 4) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Cash Flows from Operating Activities
Net Loss	($136)		($67)
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Distributions and equity in (earnings)/losses of unconsolidated affiliates and consolidated subsidiaries	32		-2
Depreciation and amortization	395		335
Provision for bad debts	15		21
Amortization of nuclear fuel	13		11
Amortization of financing costs and debt discount/premiums	-4		-5
Amortization of intangibles and out-of-market contracts	19		13
Amortization of unearned equity compensation	11		8
Changes in deferred income taxes and liability for uncertain tax benefits	-83		-111
Changes in nuclear decommissioning trust liability	-3		5
Changes in derivative instruments	261		525
Changes in collateral deposits supporting energy risk management activities	-213		-407
Cash used by changes in other working capital	-33		65
Net Cash (Used)/Provided by Operating Activities	260		391
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	0		0
Acquisitions of businesses, net of cash acquired	-1		-218
Capital expenditures	-252		-237
(Increase)/decrease in restricted cash, net	-11		3
Increase in restricted cash - U.S. DOE projects	25		56
Decrease/(increase) in notes receivable	5		1
Investments in nuclear decommissioning trust fund securities	-193		-188
Proceeds from the sale of nuclear decommissioning trust fund securities	196		183
Proceeds from renewable energy grants and state rebates	2		387
Proceeds from sale of assets, net of cash disposed of	0		77
Cash proceeds to fund cash grant bridge loan payment	0		57
Other	-41		3
Net Cash Provided/(Used) by Investing Activities	-270		124
Cash Flows from Financing Activities
Proceeds from intercompany loans	0		0
Payment of dividends to common and preferred stockholders	-51		-41
Payment of intercompany dividends			-41
Payment for treasury stock	-79		0
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	40		-223
Contributions and sale proceeds from noncontrolling interest in subsidiaries	25		-9
Proceeds from issuance of long-term debt	248		1,564
Proceeds from issuance of common stock	1		3
Payment of debt issuance costs	0		-23
Payments for short and long-term debt	-94		-873
Net Cash (Used)/Provided by Financing Activities	40		416
Effect of exchange rate changes on cash and cash equivalents	18		2
Net Increase/(Decrease) in Cash and Cash Equivalents	48		933
Cash and Cash Equivalents at Beginning of Period	2,116		2,254
Cash and Cash Equivalents at End of Period	2,164		3,187
Guarantor Subsidiaries
Cash Flows from Operating Activities
Net Loss	83		168
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Depreciation and amortization	204		198
Net Cash (Used)/Provided by Operating Activities	820		446
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	-737		-405
Acquisitions of businesses, net of cash acquired	0		0
Capital expenditures	-89		-73
(Increase)/decrease in restricted cash, net	0		0
Increase in restricted cash - U.S. DOE projects	0		-4
Decrease/(increase) in notes receivable	0		0
Investments in nuclear decommissioning trust fund securities	-193		-188
Proceeds from the sale of nuclear decommissioning trust fund securities	196		183
Proceeds from renewable energy grants and state rebates	0		0
Proceeds from sale of assets, net of cash disposed of			0
Cash proceeds to fund cash grant bridge loan payment			0
Other	-2		7
Net Cash Provided/(Used) by Investing Activities	-825		-480
Cash Flows from Financing Activities
Proceeds from intercompany loans	0		0
Payment of dividends to common and preferred stockholders	0
Payment of intercompany dividends			0
Payment for treasury stock	0
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	0		0
Proceeds from issuance of common stock	0		0
Payment of debt issuance costs			0
Payments for short and long-term debt	0		0
Net Cash (Used)/Provided by Financing Activities	0		0
Effect of exchange rate changes on cash and cash equivalents	0		0
Net Increase/(Decrease) in Cash and Cash Equivalents	-5		-34
Cash and Cash Equivalents at Beginning of Period	18		56
Cash and Cash Equivalents at End of Period	13		22
Non-Guarantor Subsidiaries
Cash Flows from Operating Activities
Net Loss	-75		-13
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Depreciation and amortization	186		134
Net Cash (Used)/Provided by Operating Activities	-430		430
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	328		4
Acquisitions of businesses, net of cash acquired	-1		-25
Capital expenditures	-157		-162
(Increase)/decrease in restricted cash, net	-11		3
Increase in restricted cash - U.S. DOE projects	24		60
Decrease/(increase) in notes receivable	5		1
Investments in nuclear decommissioning trust fund securities	0		0
Proceeds from the sale of nuclear decommissioning trust fund securities	0		0
Proceeds from renewable energy grants and state rebates	2		387
Proceeds from sale of assets, net of cash disposed of			0
Cash proceeds to fund cash grant bridge loan payment			57
Other	-2		-4
Net Cash Provided/(Used) by Investing Activities	188		321
Cash Flows from Financing Activities
Proceeds from intercompany loans	0		0
Payment of dividends to common and preferred stockholders	0
Payment of intercompany dividends			0
Payment for treasury stock	0
Net (payments for)/receipts from settlement of acquired derivatives that include financing elements	40		-223
Contributions and sale proceeds from noncontrolling interest in subsidiaries	25		-9
Proceeds from issuance of long-term debt	221		464
Proceeds from issuance of common stock	0		0
Payment of debt issuance costs			-9
Payments for short and long-term debt	-89		-405
Net Cash (Used)/Provided by Financing Activities	147		-164
Effect of exchange rate changes on cash and cash equivalents	18		2
Net Increase/(Decrease) in Cash and Cash Equivalents	-77		589
Cash and Cash Equivalents at Beginning of Period	1,455		870
Cash and Cash Equivalents at End of Period	1,378		1,459
NRG Energy, Inc.
Cash Flows from Operating Activities
Net Loss	-126		-52
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Depreciation and amortization	5		3
Net Cash (Used)/Provided by Operating Activities	-539		-886
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	409		401
Acquisitions of businesses, net of cash acquired	0		-193
Capital expenditures	-6		-2
(Increase)/decrease in restricted cash, net	0		0
Increase in restricted cash - U.S. DOE projects	1		0
Decrease/(increase) in notes receivable	0		0
Investments in nuclear decommissioning trust fund securities	0		0
Proceeds from the sale of nuclear decommissioning trust fund securities	0		0
Proceeds from renewable energy grants and state rebates	0		0
Proceeds from sale of assets, net of cash disposed of			77
Cash proceeds to fund cash grant bridge loan payment			0
Other	-37		0
Net Cash Provided/(Used) by Investing Activities	367		283
Cash Flows from Financing Activities
Proceeds from intercompany loans	409		401
Payment of dividends to common and preferred stockholders	-51
Payment of intercompany dividends			-41
Payment for treasury stock	-79
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	27		1,100
Proceeds from issuance of common stock	1		3
Payment of debt issuance costs			-14
Payments for short and long-term debt	-5		-468
Net Cash (Used)/Provided by Financing Activities	302		981
Effect of exchange rate changes on cash and cash equivalents	0		0
Net Increase/(Decrease) in Cash and Cash Equivalents	130		378
Cash and Cash Equivalents at Beginning of Period	643		1,328
Cash and Cash Equivalents at End of Period	773		1,706
Eliminations
Cash Flows from Operating Activities
Net Loss	-18	[1]	-170	[2]
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Depreciation and amortization	0	[1]	0	[2]
Net Cash (Used)/Provided by Operating Activities	409	[1]	401	[1]
Cash Flows from Investing Activities
Intercompany loans to subsidiaries	0	[1]	0	[1]
Acquisitions of businesses, net of cash acquired	0	[1]	0	[1]
Capital expenditures	0	[1]	0	[1]
(Increase)/decrease 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 the sale of nuclear decommissioning trust fund securities	0	[1]	0	[1]
Proceeds from renewable energy grants and state rebates	0	[1]	0	[1]
Proceeds from sale of assets, net of cash disposed of			0	[1]
Cash proceeds to fund cash grant bridge loan payment			0	[1]
Other	0	[1]	0	[1]
Net Cash Provided/(Used) by Investing Activities	0	[1]	0	[1]
Cash Flows from Financing Activities
Proceeds from intercompany loans	-409	[1]	-401	[1]
Payment of dividends to common and preferred stockholders	0	[1]
Payment of intercompany dividends			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	[1]	0	[1]
Payment of debt issuance costs			0	[1]
Payments for short and long-term debt	0	[1]	0	[1]
Net Cash (Used)/Provided by Financing Activities	-409	[1]	-401	[1]
Effect of exchange rate changes on cash and cash equivalents	0	[1]	0	[1]
Net Increase/(Decrease) 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]
[1]	All significant intercompany transactions have been eliminated in consolidation.
[2]	(a)All significant intercompany transactions have been eliminated in consolidation.