Clearway Energy (CWEN) 10-Q 3 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2018shares
Document And Entity Information [Abstract]
Entity Registrant Name	NRG Yield, Inc.
Entity Central Index Key	1,567,683
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Common Class A [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding	34,586,250
Common Class B [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding	42,738,750
Common Class C [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding	65,343,576
Common Class D [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding	42,738,750

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Operating Revenues
Total operating revenues		$ 225	$ 221	[1]
Operating Costs and Expenses
Cost of operations		89	85	[1]
Depreciation and amortization		81	77	[1]
General and administrative		5	4	[1]
Acquisition-related transaction and integration costs		1	1	[1]
Total operating costs and expenses		176	167	[1]
Operating Income		49	54	[1]
Other Income (Expense)
Equity in earnings of unconsolidated affiliates		4	19	[1]
Other income, net		1	1	[1]
Loss on debt extinguishment		0	(2)	[1]
Interest expense		(55)	(75)	[1]
Total other expense, net		(50)	(57)	[1]
Loss Before Income Taxes		(1)	(3)	[1]
Income tax benefit		(1)	(1)	[1]
Net Loss		0	(2)	[1]
Less: Pre-acquisition net income of Drop Down Assets		4	13	[1]
Net Loss Excluding Pre-acquisition Net Income of Drop Down Assets		(4)	(15)	[1]
Less: Loss attributable to noncontrolling interests		(20)	(12)	[1]
Net Income (Loss) Attributable to NRG Yield, Inc.		$ 16	$ (3)	[1]
Earnings (Loss) Per Share Attributable to NRG Yield, Inc. Class A and Class C Common Stockholders
Dividends Per Common Share, Cash Paid		$ 0.298
Common Class C [Member]
Earnings Per Share, Basic	[2]	$ 0.16	$ (0.03)
Other Income (Expense)
Net Income (Loss) Attributable to NRG Yield, Inc.	[2]	$ 10	$ (2)
Earnings (Loss) Per Share Attributable to NRG Yield, Inc. Class A and Class C Common Stockholders
Weighted Average Number of Shares Outstanding, Basic and Diluted	[2]	65	63
Earnings (Loss) per Weighted Average Class A and Class C Common Share - Basic and Diluted	[2]	$ 0.16	$ (0.03)
Dividends Per Common Share, Cash Paid		$ 0.298	$ 0.260
Common Class A [Member]
Other Income (Expense)
Net Income (Loss) Attributable to NRG Yield, Inc.	[2]	$ 6	$ (1)
Earnings (Loss) Per Share Attributable to NRG Yield, Inc. Class A and Class C Common Stockholders
Weighted Average Number of Shares Outstanding, Basic and Diluted	[2]	35	35
Earnings (Loss) per Weighted Average Class A and Class C Common Share - Basic and Diluted	[2]	$ 0.16	$ (0.03)
Dividends Per Common Share, Cash Paid		$ 0.298	$ 0.260
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	(a) Basic and diluted earnings (loss) per share might not recalculate due to presenting values in millions rather than whole dollars.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	[1]
Net loss	$ 0	$ (2)
Other Comprehensive Gain, net of tax
Unrealized gain on derivatives, net of income tax expense of $3 and $1	17	6
Other comprehensive gain	17	6
Comprehensive Income	17	4
Less: Pre-acquisition net income of Drop Down Assets	4	13
Less: Comprehensive loss attributable to noncontrolling interests	(11)	(9)
Comprehensive Income Attributable to NRG Yield, Inc.	$ 24	$ 0
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Consolidated Statements of Com4

Consolidated Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gain/loss on derivatives, income tax expense /(benefit)	$ 3	$ 1

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 173,000,000	$ 148,000,000	[1]
Restricted cash	104,000,000	168,000,000	[1]
Accounts receivable — trade	82,000,000	95,000,000	[1]
Inventory	39,000,000	39,000,000	[1]
Notes receivable	9,000,000	13,000,000	[1]
Prepayments and other current assets	18,000,000	19,000,000	[1]
Total current assets	425,000,000	482,000,000	[1]
Property, plant and equipment, net	5,340,000,000	5,410,000,000	[1]
Other Assets
Equity investments in affiliates	1,169,000,000	1,178,000,000	[1]
Intangible assets, net	1,210,000,000	1,228,000,000	[1]
Derivative instruments	16,000,000	1,000,000	[1]
Deferred income taxes	129,000,000	128,000,000	[1]
Other non-current assets	73,000,000	62,000,000	[1]
Total other assets	2,597,000,000	2,597,000,000	[1]
Total Assets	8,362,000,000	8,489,000,000	[1]
Current Liabilities
Current portion of long-term debt	698,000,000	339,000,000	[1]
Accounts payable — trade	40,000,000	46,000,000	[1]
Accounts payable — affiliate	54,000,000	49,000,000	[1]
Derivative instruments	9,000,000	18,000,000	[1]
Accrued expenses and other current liabilities	58,000,000	88,000,000	[1]
Total current liabilities	859,000,000	540,000,000	[1]
Other Liabilities
Long-term debt	5,261,000,000	5,659,000,000	[1]
Derivative instruments	17,000,000	31,000,000	[1]
Other non-current liabilities	99,000,000	100,000,000	[1]
Total non-current liabilities	5,377,000,000	5,790,000,000	[1]
Total Liabilities	6,236,000,000	6,330,000,000	[1]
Commitments and Contingencies	0	0
Stockholders' Equity
Preferred stock, $0.01 par value; 10,000,000 shares authorized; none issued	0	0	[1]
Class A, Class B, Class C and Class D common stock, $0.01 par value; 3,000,000,000 shares authorized (Class A 500,000,000, Class B 500,000,000, Class C 1,000,000,000, Class D 1,000,000,000); 185,407,326 shares issued and outstanding (Class A 34,586,250, Class B 42,738,750, Class C 65,343,576, Class D 42,738,750) at March 31, 2018 and 184,780,837 shares issued and outstanding (Class A 34,586,250, Class B 42,738,750, Class C 64,717,087, Class D 42,738,750) at December 31, 2017	1,000,000	1,000,000	[1]
Additional paid-in capital	1,827,000,000	1,843,000,000	[1]
Accumulated deficit	(53,000,000)	(69,000,000)	[1]
Accumulated other comprehensive loss	(20,000,000)	(28,000,000)	[1]
Noncontrolling interest	371,000,000	412,000,000	[1]
Total Stockholders' Equity	2,126,000,000	2,159,000,000	[1]
Total Liabilities and Stockholders' Equity	$ 8,362,000,000	$ 8,489,000,000	[1]
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Common Stock, Par or Stated Value Per Share	$ 0.01
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Commitments and Contingencies	$ 0	$ 0
Common Class A [Member]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Issued	34,586,250	34,586,250
Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Class B [Member]
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Issued	42,738,750	42,738,750
Common Class C [Member]
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Issued	65,343,576	64,717,087
Common Class D [Member]
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Issued	42,738,750	42,738,750

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	[1]
Cash Flows from Operating Activities
Net loss	$ 0	$ (2)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in earnings of unconsolidated affiliates	(4)	(19)
Distributions from unconsolidated affiliates	13	16
Depreciation and amortization	81	77
Amortization of financing costs and debt discounts	7	5
Amortization of intangibles and out-of-market contracts	17	17
Adjustment for debt extinguishment	0	(2)
Changes in deferred income taxes	(1)	(1)
Changes in derivative instruments	(23)	(8)
Loss on disposal of asset components	2	3
Changes in prepaid and accrued liabilities for tolling agreements	(36)	(36)
Changes in other working capital	9	10
Net Cash Provided by Operating Activities	65	64
Cash Flows from Investing Activities
Payments for the Drop Down Assets	42	131
Capital expenditures	(18)	(6)
Cash receipts from notes receivable	4	4
Return of investment from unconsolidated affiliates	14	16
Investments in unconsolidated affiliates	(6)	(7)
Payments for (Proceeds from) Other Investing Activities	(4)	0
Net Cash Used in Investing Activities	(44)	(124)
Cash Flows from Financing Activities
Net contributions from noncontrolling interests	30	14
Net distributions and return of capital to NRG prior to the acquisition of Drop Down Assets	0	(21)
Net proceeds from the issuance of common stock	10	7
Payments of dividends and distributions	(55)	(48)
Payments of debt issuance costs	0	3
Proceeds from the revolving credit facility	20	0
Proceeds from the issuance of long-term debt	14	41
Payments for long-term debt	(79)	(105)
Net Cash Used in Financing Activities	(60)	(115)
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(39)	(175)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	316	498
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 277	$ 323
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business NRG Yield, Inc., together with its consolidated subsidiaries, or the Company, is a dividend growth-oriented company that has historically served as the primary vehicle through which NRG owns, operates and acquires contracted renewable and conventional generation and thermal infrastructure assets. The Company believes it is well positioned to be a premier company for investors seeking stable and growing dividend income from a diversified portfolio of lower-risk assets. The Company owns a diversified portfolio of contracted renewable and conventional generation and thermal infrastructure assets in the U.S. The Company’s contracted generation portfolio collectively represents 5,118 net MW as of March 31, 2018 . Nearly all of these assets sell substantially all of their output pursuant to long-term offtake agreements with creditworthy counterparties. The weighted average remaining contract duration of these offtake agreements was approximately 15 years as of March 31, 2018 based on CAFD. The Company also owns thermal infrastructure assets with an aggregate steam and chilled water capacity of 1,319 net MWt and electric generation capacity of 123 net MW. These thermal infrastructure assets provide steam, hot and/or chilled water, and, in some instances, electricity to commercial businesses, universities, hospitals and governmental units in multiple locations, principally through long-term contracts or pursuant to rates regulated by state utility commissions. NRG Yield, Inc. consolidates the results of NRG Yield LLC through its controlling interest, with NRG's interest shown as noncontrolling interest in the financial statements. The holders of NRG Yield, Inc.'s outstanding shares of Class A and Class C common stock are entitled to dividends as declared. NRG receives its distributions from NRG Yield LLC through its ownership of NRG Yield LLC Class B and Class D units. The following table represents the structure of the Company as of March 31, 2018 : On February 6, 2018, Global Infrastructure Partners, or GIP, entered into a purchase and sale agreement with NRG, or the NRG Transaction, for the acquisition of NRG's full ownership interests in the Company and NRG's renewable development and operations platform. The NRG Transaction is subject to certain closing conditions, including customary legal and regulatory approvals. The Company expects the NRG Transaction to close in the second half of 2018. NRG is currently the Company's controlling stockholder and the Company has been highly dependent on NRG for, among other things, growth opportunities and management and administration services. In connection with the NRG Transaction, the Company entered into a Consent and Indemnity Agreement with NRG and GIP setting forth key terms and conditions of the Company's consent to the NRG Transaction. For further discussion of the NRG Transaction, refer to Item 1 - Business in the Company's 2017 Form 10-K. For risks related to the NRG Transaction and the Company's relationship with NRG see Part I, Item 1A, Risk Factors in the Company's 2017 Form 10-K. As of March 31, 2018 , the Company's operating assets are comprised of the following projects: Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Conventional El Segundo 100 % 550 Southern California Edison 2023 GenConn Devon 50 % 95 Connecticut Light & Power 2040 GenConn Middletown 50 % 95 Connecticut Light & Power 2041 Marsh Landing 100 % 720 Pacific Gas and Electric 2023 Walnut Creek 100 % 485 Southern California Edison 2023 1,945 Utility Scale Solar Agua Caliente 16 % 46 Pacific Gas and Electric 2039 Alpine 100 % 66 Pacific Gas and Electric 2033 Avenal 50 % 23 Pacific Gas and Electric 2031 Avra Valley 100 % 26 Tucson Electric Power 2032 Blythe 100 % 21 Southern California Edison 2029 Borrego 100 % 26 San Diego Gas and Electric 2038 CVSR 100 % 250 Pacific Gas and Electric 2038 Desert Sunlight 250 25 % 63 Southern California Edison 2035 Desert Sunlight 300 25 % 75 Pacific Gas and Electric 2040 Kansas South 100 % 20 Pacific Gas and Electric 2033 Roadrunner 100 % 20 El Paso Electric 2031 TA High Desert 100 % 20 Southern California Edison 2033 Utah Solar Portfolio (b) (e) 50 % 265 PacifiCorp 2036 921 Distributed Solar Apple I LLC Projects 100 % 9 Various 2032 AZ DG Solar Projects 100 % 5 Various 2025 - 2033 SPP Projects 100 % 25 Various 2026 - 2037 Other DG Projects 100 % 13 Various 2023 - 2039 52 Wind Alta I 100 % 150 Southern California Edison 2035 Alta II 100 % 150 Southern California Edison 2035 Alta III 100 % 150 Southern California Edison 2035 Alta IV 100 % 102 Southern California Edison 2035 Alta V 100 % 168 Southern California Edison 2035 Alta X (b) 100 % 137 Southern California Edison 2038 Alta XI (b) 100 % 90 Southern California Edison 2038 Buffalo Bear 100 % 19 Western Farmers Electric Co-operative 2033 Crosswinds (b) (f) 99 % 21 Corn Belt Power Cooperative 2027 Elbow Creek (b) (f) 100 % 122 NRG Power Marketing LLC 2022 Elkhorn Ridge (b) (f) 66.7 % 54 Nebraska Public Power District 2029 Forward (b) (f) 100 % 29 Constellation NewEnergy, Inc. 2017 Goat Wind (b) (f) 100 % 150 Dow Pipeline Company 2025 Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Hardin (b) (f) 99 % 15 Interstate Power and Light Company 2027 Laredo Ridge 100 % 80 Nebraska Public Power District 2031 Lookout (b) (f) 100 % 38 Southern Maryland Electric Cooperative 2030 Odin (b) (f) 99.9 % 20 Missouri River Energy Services 2028 Pinnacle 100 % 55 Maryland Department of General Services and University System of Maryland 2031 San Juan Mesa (b) (f) 75 % 90 Southwestern Public Service Company 2025 Sleeping Bear (b) (f) 100 % 95 Public Service Company of Oklahoma 2032 South Trent 100 % 101 AEP Energy Partners 2029 Spanish Fork (b) (f) 100 % 19 PacifiCorp 2028 Spring Canyon II (b) 90.1 % 29 Platte River Power Authority 2039 Spring Canyon III (b) 90.1 % 25 Platte River Power Authority 2039 Taloga 100 % 130 Oklahoma Gas & Electric 2031 Wildorado (b) (f) 100 % 161 Southwestern Public Service Company 2027 2,200 Thermal NRG Energy Center Dover LLC 100 % 103 NRG Power Marketing LLC 2018 Thermal generation 100 % 20 Various Various 123 Total net generation capacity (c) 5,241 Thermal equivalent MWt (d) 100 % 1,319 Various Various (a) Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018 . (b) Projects are part of tax equity arrangements. (c) The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs. (d) For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers. (e) Represents interests in Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC, all acquired as part of the March 2017 Drop Down Assets (ownership percentage is based upon cash to be distributed). (f) Projects are part of NRG Wind TE Holdco portfolio. In addition to the facilities owned or leased in the table above, the Company entered into partnerships to own or purchase solar power generation projects, as well as other ancillary related assets from a related party via intermediate funds. The Company does not consolidate these partnerships and accounts for them as equity method investments. The Company's net interest in these projects is 262 MW based on cash to be distributed as of March 31, 2018 . For further discussions, refer to Note 4 , Investments Accounted for by the Equity Method and Variable Interest Entities of this Form 10-Q and Note 5 , Investments Accounted for by the Equity Method and Variable Interest Entities to the consolidated financial statements included in the Company's 2017 Form 10-K. Substantially all of the Company's generation assets are under long-term contractual arrangements for the output or capacity from these assets. The thermal assets are comprised of district energy systems and combined heat and power plants that produce steam, hot water and/or chilled water and, in some instances, electricity at a central plant. Certain district energy systems are subject to rate regulation by state public utility commissions (although they may negotiate certain rates) while the other district energy systems have rates determined by negotiated bilateral contracts. As described in Note 3 , Business Acquisitions , on March 30, 2018, the Company acquired 100% of NRG's interests in Buckthorn Renewables, LLC, which owns a 154 MW construction-stage utility-scale solar generation project, or the Buckthorn Solar Drop Down Asset, for cash consideration of approximately $42 million , subject to working capital adjustments, plus assumed non-recourse debt of approximately $183 million . The project will sell power under a 25-year PPA to the City of Georgetown, Texas starting in July 2018 when it is expected to achieve commercial operation. The purchase price was funded with cash on hand and borrowings from the revolving credit facility. The acquisition of the Buckthorn Solar Drop Down Asset was accounted for as a transfer of entities under common control. The accounting guidance requires retrospective combination of the entities for all periods presented as if the combinations had been in effect from the beginning of the financial statement period or from the date the entities were under common control (if later than the beginning of the financial statement period). The recast of the Company's financial statements for the Buckthorn Solar Drop Down Asset did not affect the historical net income attributable to NRG Yield, Inc., weighted average number of shares outstanding, earnings per share or dividends. Additionally, as described in Note 3 , Business Acquisitions , during the year ended December 31, 2017, the Company acquired the November 2017 Drop Down Assets and August 2017 Drop Down Assets from NRG. Similarly to the Buckthorn Solar Drop Down Asset, the Company recast its historical financial statements to combine the entities for the periods presented as if the combinations had been in effect from the beginning of the financial statements period. The recast of the Company's financial statements for the November 2017 Drop Down Assets and August 2017 Drop Down Assets did not affect the historical net income attributable to NRG Yield, Inc., weighted average number of shares outstanding, earnings per share or dividends. The accompanying unaudited interim 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 GAAP 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 included in the Company's 2017 Form 10-K. Interim results are not necessarily indicative of results for a full year. In the opinion of management, the accompanying unaudited interim 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, 2018 , and the results of operations, comprehensive income (loss) and cash flows for the three months ended March 31, 2018 and 2017 .

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions. These estimates and assumptions impact the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could be different from these estimates. Accumulated Depreciation, Accumulated Amortization The following table presents the accumulated depreciation included in the property, plant and equipment, net, and accumulated amortization included in intangible assets, net, respectively, as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (In millions) Property, Plant and Equipment Accumulated Depreciation $ 1,358 $ 1,285 Intangible Assets Accumulated Amortization 255 237 Noncontrolling Interests Stockholders' equity represents the equity associated with the Class A and Class C common stockholders, the equity associated with the Class B and Class D common stockholder, NRG, and the third-party interests under certain tax equity arrangements are classified as noncontrolling interests. The following table reflects the changes in the Company's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 as previously reported $ 391 Net Assets of Buckthorn Solar Drop Down Asset as of December 31, 2017 21 Balance as of December 31, 2017 as recast $ 412 Capital contributions from tax equity investors, net of distributions 30 Payment for the Buckthorn Solar Drop Down Asset (42 ) Pre-acquisition net income of the Buckthorn Solar Drop Down Asset 4 Comprehensive loss (11 ) Distributions to NRG, net (22 ) Balance as of March 31, 2018 $ 371 NRG Yield LLC Distributions to NRG The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the three months ended March 31, 2018 : First Quarter 2018 Distributions per Class B Unit $ 0.298 Distributions per Class D Unit $ 0.298 On April 24, 2018 , NRG Yield LLC declared a distribution on its Class A, Class B, Class C and Class D units of $0.309 per unit payable on June 15, 2018 to unit holders of record as of June 1, 2018 . Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606, Revenue from Contracts with Customers, or Topic 606, using the modified retrospective method applied to contracts which were not completed as of the adoption date, with no adjustment required to the financial statements upon adoption. Following the adoption of the new standard, the Company’s revenue recognition of its contracts with customers remains materially consistent with its historical practice. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company's policies with respect to its various revenue streams are detailed below. In general, the Company applies the invoicing practical expedient to recognize revenue for the revenue streams detailed below, except in circumstances where the invoiced amount does not represent the value transferred to the customer. Thermal Revenues Steam and chilled water revenue is recognized as the Company transfers the product to the customer, based on customer usage as determined by meter readings taken at month-end. Some locations read customer meters throughout the month, and recognize estimated revenue for the period between meter read date and month-end. For thermal contracts, the Company’s performance obligation to deliver steam and chilled water is satisfied over time and revenue is recognized based on the invoiced amount. The Thermal Business subsidiaries collect and remit state and local taxes associated with sales to their customers, as required by governmental authorities. These taxes are presented on a net basis in the income statement. As contracts for steam and chilled water are long-term contracts, the Company has performance obligations under these contracts that have not yet been satisfied. These performance obligations have transaction prices that are both fixed and variable, and that vary based on the contract duration, customer type, inception date and other contract-specific factors. For the fixed price contracts, the Company cannot accurately estimate the amount of its unsatisfied performance obligations as it will vary based on customer usage, which will depend on factors such as weather and customer activity. Power Purchase Agreements, or PPAs The majority of the Company’s revenues are obtained through PPAs or other contractual agreements. Energy, capacity and where applicable, renewable attributes, from the majority of the Company’s renewable energy assets and certain conventional energy plants is sold through long-term PPAs and tolling agreements to a single counterparty, which is often a utility or commercial customer. The majority of these PPAs are accounted for as leases. ASC 840 requires the minimum lease payments received to be amortized over the term of the lease and contingent rentals are recorded when the achievement of the contingency becomes probable. Judgment is required by management in determining the economic life of each generating facility, in evaluating whether certain lease provisions constitute minimum payments or represent contingent rent and other factors in determining whether a contract contains a lease and whether the lease is an operating lease or capital lease. Renewable Energy Credits As stated above, renewable energy credits, or RECs, are usually sold through long-term PPAs. Revenue from the sale of self-generated RECs is recognized when related energy is generated and simultaneously delivered even in cases where there is a certification lag as it has been deemed to be perfunctory. In a bundled contract to sell energy, capacity and/or self-generated RECs, all performance obligations are deemed to be delivered at the same time and hence, timing of recognition of revenue for all performance obligations is the same and occurs over time. In such cases, it is often unnecessary to allocate transaction price to multiple performance obligations. Sale of Emission Allowances The Company records its bank of emission allowances as part of intangible assets. From time to time, management may authorize the transfer of emission allowances in excess of usage from the Company's emission bank to intangible assets held-for-sale for trading purposes. The Company records the sale of emission allowances on a net basis within operating revenue in the Company's consolidated statements of operations. Disaggregated Revenues The following table represents the Company’s disaggregation of revenue from contracts with customers for the three months ended March 31, 2018 along with the reportable segment for each category: (In millions) Conventional Generation Renewables Thermal Total Energy revenue (a) $ 1 $ 112 $ 1 $ 114 Capacity revenue (a) 79 — 3 82 Contract amortization (1 ) (15 ) (1 ) (17 ) Other revenue — 1 45 46 Total operating revenue 79 98 48 225 Less: Lease revenue (80 ) (101 ) — (181 ) Less: Contract amortization 1 15 1 17 Total revenue from contracts with customers $ — $ 12 $ 49 $ 61 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 1 $ 101 $ — $ 102 Capacity Revenue 79 — — 79 Contract Amortization Assets and liabilities recognized from power sales agreements assumed through acquisitions related to the sale of electric capacity and energy in future periods for which the fair value has been determined to be significantly less (more) than market are amortized to revenue over the term of each underlying contract based on actual generation and/or contracted volumes or on a straight-line basis, where applicable. Contract Balances The following table reflects the contract assets and liabilities included on the Company’s balance sheet as of March 31, 2018: (In millions) March 31, 2018 Accounts receivable, net - Contracts with customers $ 26 Accounts receivable, net - Leases 56 Total accounts receivable, net $ 82 Income Taxes NRG Yield, Inc. is included in certain NRG consolidated unitary state tax return filings which is reflected in NRG Yield, Inc.'s state effective tax rate. If NRG Yield, Inc. filed under a separate standalone methodology, there would be no material change to the state tax benefit as of March 31, 2018 . Reclassifications Certain prior-year amounts have been reclassified for comparative purposes. Recent Accounting Developments - Not Yet Adopted ASU 2016-02 — In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), or Topic 842, with the objective to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and to improve financial reporting by expanding the related disclosures. The guidance in Topic 842 provides that a lessee that may have previously accounted for a lease as an operating lease under current GAAP should recognize the assets and liabilities that arise from a lease on the balance sheet. In addition, Topic 842 expands the required quantitative and qualitative disclosures with regards to lease arrangements. The Company will adopt the standard effective January 1, 2019 and expects to elect certain of the practical expedients permitted, including the expedient that permits the Company to retain its existing lease assessment and classification. The Company is currently working through an adoption plan and evaluating the anticipated impact on the Company's results of operations, cash flows and financial position. While the Company is currently evaluating the impact the new guidance will have on its financial position and results of operations, the Company expects to recognize lease liabilities and right of use assets. The extent of the increase to assets and liabilities associated with these amounts remains to be determined pending the Company’s review of its existing lease contracts and service contracts which may contain embedded leases. While this review is still in process, the Company believes the adoption of Topic 842 may be material to its financial statements. The Company is continuing to monitor potential changes to Topic 842 that have been proposed by the FASB and will assess any necessary changes to the implementation as the guidance is updated.

Business Acquisitions Business

Business Acquisitions Business Acquisitions (Notes)	3 Months Ended
	Mar. 31, 2018
Business Acquisitions [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	Business Acquisitions 2018 Acquisitions Central CA Fuel Cell 1, LLC — On April 18, 2018 , the Company acquired the Central CA Fuel Cell 1, LLC project in Tulare, California from FuelCell Energy Finance, Inc., for cash consideration of $11 million , subject to working capital adjustments. The project will add an additional 2.8 MW of thermal capacity to the Company's portfolio, with a 20 -year PPA contract with the City of Tulare. The transaction will be reflected in the Company's Thermal segment. Buckthorn Solar Drop Down Asset — On March 30, 2018 , the Company acquired 100% of NRG's interests in Buckthorn Renewables, LLC, which owns a 154 MW construction-stage utility-scale solar generation project, located in Texas, or the Buckthorn Solar Drop Down Asset, for cash consideration of approximately $42 million , subject to working capital adjustments. The Company also assumed non-recourse debt of $ 183 million and non-controlling interest of $19 million (as of acquisition date) attributable to the Class A member, as further described below. A portion of non-recourse debt is expected to convert to a term loan and the remainder of the outstanding debt will be paid down with the remaining contributions from the Class A member upon the project achieving substantial completion in May 2018. The purchase price for the Buckthorn Solar Drop Down Asset was funded with cash on hand and borrowings from the Company's revolving credit facility. The assets and liabilities transferred to the Company relate to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combinations - Related Issues . The difference between the cash paid and historical value of the entities' equity was recorded as a distribution to NRG and decreased the balance of its noncontrolling interest. Because the transaction constituted a transfer of net assets under common control, the guidance requires retrospective combination of the entities for all periods presented as if the combination has been in effect since the inception of common control. Buckthorn Solar Portfolio, LLC, a wholly owned subsidiary of Buckthorn Renewables, LLC, is the Class B member in a tax equity partnership, Buckthorn Holdings, LLC, the owner of the Buckthorn Solar Drop Down Asset. The Class A member is a tax equity investor, or TE investor, who receives 99% of allocations of taxable income and other items through the six month anniversary of the placed in service date, at which time the allocations change to 67% through the last calendar year before the flip point, and then back to 99% through the flip point (which occurs when the TE Investor obtains a specified return on its initial investment), at which time the allocations to the TE Investor change to 5% for all the periods thereafter. Before the flip point, the TE investor would receive a priority distribution of distributable cash, as defined, plus a percentage of remaining distributable cash after the priority distribution subject to a percentage cap. On March 30, 2018, the TE Investor made its initial capital contribution of $19 million with the remaining contributions from each partner targeted to be funded in the second quarter of 2018. The project will sell power under a 25-year PPA to the City of Georgetown, Texas starting in July 2018 when it is expected to achieve commercial operation. The following is a summary of net assets transferred in connection with the acquisition of the Buckthorn Solar Drop Down Asset as of March 31, 2018: (In millions) Assets: Current assets $ 20 Property, plant and equipment 212 Non-current assets 3 Total assets 235 Liabilities: Debt (Current and non-current) (a) 176 Other current and non-current liabilities 15 Total liabilities 191 Less: noncontrolling interest 19 Net assets acquired $ 25 (a) Net of $7 million of net debt issuance costs. The following table presents the historical information summary combining the financial information for the Buckthorn Drop Down Asset transferred in connection with the acquisition: As of December 31, 2017 (In millions) As Previously Reported Buckthorn Solar Drop Down Asset As Currently Reported Assets: Current assets $ 482 $ — $ 482 Property, plant and equipment 5,204 206 5,410 Non-current assets 2,597 — 2,597 Total assets 8,283 206 8,489 Liabilities: Debt 5,837 161 5,998 Other current and non-current liabilities 308 24 332 Total liabilities 6,145 185 6,330 Net assets $ 2,138 $ 21 $ 2,159 2017 Acquisitions November 2017 Drop Down Assets — On November 1, 2017, the Company acquired a 38 MW solar portfolio primarily comprised of assets from NRG's Solar Power Partners (SPP) funds and other projects developed by NRG , for cash consideration of $74 million , including working capital adjustments, plus assumed non-recourse debt of $26 million . The purchase price for the November 2017 Drop Down Assets was funded with cash on hand. The assets and liabilities transferred to the Company relate to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combinations - Related Issues . The difference between the cash paid and historical value of the entities' equity was recorded as a contribution from NRG and increased the balance of its noncontrolling interest. Because the transaction constituted a transfer of net assets under common control, the guidance requires retrospective combination of the entities for all periods presented as if the combination has been in effect since the inception of common control. August 2017 Drop Down Assets — On August 1, 2017, the Company acquired the remaining 25% interest in NRG Wind TE Holdco, a portfolio of 12 wind projects, from NRG for total cash consideration of $44 million , including working capital adjustments. The purchase agreement also included potential additional payments to NRG dependent upon actual energy prices for merchant periods beginning in 2027, which were estimated and accrued as contingent consideration in the amount of $8 million . The Company originally acquired 75% of NRG Wind TE Holdco on November 3, 2015, or November 2015 Drop Down Assets, which were consolidated with 25% of the net assets recorded as noncontrolling interest. The assets and liabilities transferred to the Company related to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combination - Related Issues. As the Company had reflected NRG's 25% ownership of NRG Wind TE Holdco in noncontrolling interest, the difference between the cash paid of $44 million , net of the contingent consideration of $8 million , and the historical value of the remaining 25% of $87 million as of July 31, 2017, was recorded as an adjustment to NRG's noncontrolling interest. Since the transaction constituted a transfer of entities under common control, the accounting guidance requires retrospective combination of the entities for all periods presented as if the combination has been in effect from the beginning of the financial statement period or from the date the entities were under common control (if later than the beginning of the financial statement period). The following tables present a summary of the Company's historical information combining the financial information for the November 2017 Drop Down Assets and August 2017 Drop Down Assets transferred in connection with the acquisition: Three months ended March 31, 2017 As Previously Reported (a) November 2017 Drop Down Assets August 2017 Drop Down Assets As Currently Reported (In millions) Total operating revenues $ 218 $ 3 $ — $ 221 Operating income 54 — — 54 Net loss (1 ) (1 ) — (2 ) Less: Pre-acquisition net income of Drop Down Assets 12 (1 ) 2 13 Less: Loss attributable to noncontrolling interests (10 ) — (2 ) (12 ) Net loss attributable to NRG Yield, Inc. (3 ) — — (3 ) (a) As previously reported in the Company's Form 10-Q for the quarter ended March 31, 2017 March 2017 Drop Down Assets — On March 27, 2017, the Company acquired the following interests from NRG: (i) Agua Caliente Borrower 2 LLC, which owns a 16% interest (approximately 31% of NRG's 51% interest) in the Agua Caliente solar farm, one of the ROFO Assets, representing ownership of approximately 46 net MW of capacity and (ii) NRG's interests in the Utah Solar Portfolio. Agua Caliente is located in Yuma County, AZ and sells power subject to a 25 -year PPA with Pacific Gas and Electric, with 22 years remaining on that contract. The seven utility-scale solar farms in the Utah Solar Portfolio are owned by the following entities: Four Brothers Capital, LLC, Iron Springs Capital, LLC, and Granite Mountain Capital, LLC. These utility-scale solar farms achieved commercial operations in 2016, sell power subject to 20 -year PPAs with PacifiCorp, a subsidiary of Berkshire Hathaway and are part of a tax equity structure with Dominion Solar Projects III, Inc., or Dominion, through which the Company is entitled to receive 50% of cash to be distributed, as further described below. The Company paid cash consideration of $128 million , which includes $4 million of final working capital adjustment paid to the Company by NRG during the period ended March 31, 2018. The acquisition of the March 2017 Drop Down Assets was funded with cash on hand. The Company recorded the acquired interests as equity method investments. The Company also assumed non-recourse debt of $41 million and $287 million on Agua Caliente Borrower 2 LLC and the Utah Solar Portfolio, respectively, as well as its pro-rata share of non-recourse project-level debt of Agua Caliente Solar LLC, as further described in Note 4 , Investments Accounted for by the Equity Method and Variable Interest Entities . The assets and liabilities transferred to the Company relate to interests under common control by NRG and were recorded at historical cost in accordance with ASC 805-50, Business Combination - Related Issues. The difference between the cash paid and the historical value of the entities' equity of $8 million was recorded as an adjustment to NRG's noncontrolling interest. Since the transaction constituted a transfer of entities under common control, the accounting guidance requires retrospective combination of the entities for all periods presented as if the combination has been in effect from the beginning of the financial statement period or from the date the entities were under common control (if later than the beginning of the financial statement period).

Variable Interest Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments Accounted for by the Equity Method and Variable Interest Entities	Investments Accounted for by the Equity Method and Variable Interest Entities Entities that are Consolidated The Company has a controlling financial interest in certain entities which have been identified as VIEs under ASC 810, Consolidations, or ASC 810. These arrangements are primarily related to tax equity arrangements entered into with third parties in order to monetize certain tax credits associated with wind facilities, as further described in Note 5 , Investments Accounted for by the Equity Method and Variable Interest Entities , to the consolidated financial statements included in the Company's 2017 Form 10-K. Buckthorn Renewables, LLC - As described in Note 3 , Business Acquisitions , on March 30, 2018, the Company acquired 100% of NRG’s interest in a 154 MW construction-stage utility-scale solar generation project, Buckthorn Renewables, LLC, which owns 100% interest in Buckthorn Solar Portfolio, LLC, which in turn owns 100% of the Class B membership interests in Buckthorn Holdings, LLC for total consideration of approximately $42 million , subject to working capital adjustments. Buckthorn Holdings, LLC is a tax equity fund, which is a variable interest entity that is consolidated by Buckthorn Solar Portfolio, LLC. The Company is the primary beneficiary, through its position as managing member, and indirectly consolidates Buckthorn Holdings, LLC through Buckthorn Solar Portfolio, LLC. The Class A member is a tax equity investor who made its initial capital contribution of $19 million on March 30, 2018, which is reflected as noncontrolling interest on the Company’s consolidated balance sheet. The project is expected to begin commercial operations in July 2018, at which time the remaining contributions from each partner would be funded. The Company utilizes the HLBV method to determine the net income or loss allocated to the tax equity investor noncontrolling interest. Summarized financial information for the Company's consolidated VIEs consisted of the following as of March 31, 2018 : (In millions) NRG Wind TE Holdco Alta Wind TE Holdco Spring Canyon Buckthorn Renewables, LLC Other current and non-current assets $ 172 $ 18 $ 2 $ 23 Property, plant and equipment 369 430 94 212 Intangible assets 2 259 — — Total assets 543 707 96 235 Current and non-current liabilities 195 8 5 191 Total liabilities 195 8 5 191 Noncontrolling interest 9 77 50 19 Net assets less noncontrolling interests $ 339 $ 622 $ 41 $ 25 Entities that are not Consolidated The Company has interests in entities that are considered VIEs under ASC 810, but for which it is not considered the primary beneficiary. The Company accounts for its interests in these entities under the equity method of accounting, as further described in Note 5 , Investments Accounted for by the Equity Method and Variable Interest Entities , to the consolidated financial statements included in the Company's 2017 Form 10-K. The Company's maximum exposure to loss as of March 31, 2018 is limited to its equity investment in the unconsolidated entities, as further summarized in the table below: (In millions) Maximum exposure to loss Four Brothers Solar, LLC $ 209 GenConn Energy LLC 100 Granite Mountain Holdings, LLC 76 NRG DGPV Holdco 1 LLC 73 NRG DGPV Holdco 3 LLC 62 NRG DGPV Holdco 2 LLC 61 Iron Springs Holdings, LLC 53 NRG RPV Holdco 1 LLC 52 NRG DGPV Holdco 3 LLC — The Company invested $6 million of cash during the three months ended March 31, 2018 into DGPV Holdco 3 LLC and recorded $16 million due to NRG in accounts payable - affiliate as of March 31, 2018 to be funded in tranches as the project milestones are completed. The Company owns approximately 59 MW of distributed solar capacity, based on cash to be distributed, with a weighted average remaining contract life of approximately 22 years as of March 31, 2018 . Utah Solar Portfolio — As described in Note 3 , Business Acquisitions , on March 27, 2017, as part of the March 2017 Drop Down Assets acquisition, the Company acquired from NRG 100% of the Class A equity interests in the Utah Solar Portfolio, comprised of Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC. The Class B interests of the Utah Solar Portfolio are owned by a tax equity investor, who receives 99% of allocations of taxable income and other items until the flip point, which occurs when the tax equity investor obtains a specified return on its initial investment, at which time the allocations to the tax equity investor change to 50% . The Company generally receives 50% of distributable cash throughout the term of the tax-equity arrangements. The three entities comprising the Utah Solar Portfolio are VIEs. As the Company is not the primary beneficiary, the Company uses the equity method of accounting to account for its interests in the Utah Solar Portfolio. The Company utilizes the HLBV method to determine its share of the income or losses in the investees. The following tables present summarized financial information for the Company's significant equity method investments: Three months ended March 31, (In millions) 2018 2017 Income Statement Data: DGPV entities (a) Operating revenues $ 11 $ 5 Operating loss — (1 ) Net income (loss) 3 (2 ) March 31, 2018 December 31, 2017 Balance Sheet Data: (In millions) DGPV entities (a) Current assets $ 92 $ 74 Non-current assets 718 671 Current liabilities 84 83 Non-current liabilities 236 216 Redeemable noncontrolling interest 42 44 (a) Includes DGPV Holdco 1, DGPV Holdco 2, and DGPV Holdco 3 Non-recourse project-level debt of unconsolidated affiliates Agua Caliente Financing — As described in Note 3 , Business Acquisitions , on March 27, 2017, the Company acquired a 16% interest in the Agua Caliente solar facility through its acquisition of Agua Caliente Borrower 2 LLC. As of March 31, 2018 , Agua Caliente Solar LLC, the direct owner of the Agua Caliente solar facility, had $815 million outstanding under the Agua Caliente financing agreement with the Federal Financing Bank, or FFB, borrowed to finance the costs of constructing the facility. The Company's pro-rata share of the Agua Caliente financing arrangement was $130 million as of March 31, 2018 . Amounts borrowed under the Agua Caliente financing agreement accrue interest at a fixed rate based on U.S. Treasury rates plus a spread of 0.375% , mature in 2037 and are secured by the assets of Agua Caliente Solar LLC. The loans provided by the FFB are guaranteed by the U.S. DOE.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair Value Accounting under ASC 820 ASC 820 establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows: • Level 1—quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date. • Level 2—inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. • Level 3—unobservable inputs for the asset or liability only used when there is little, if any, market activity for the asset or liability at the measurement date. In accordance with ASC 820, the Company determines the level in the fair value hierarchy within which each fair value measurement in its entirety falls, based on the lowest level input that is significant to the fair value measurement. For cash and cash equivalents, restricted cash, accounts receivable, accounts receivable — affiliate, accounts payable, current portion of the accounts payable — affiliates, accrued expenses and other liabilities, the carrying amounts approximate 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 the Company’s recorded financial instruments not carried at fair market value are as follows: As of March 31, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable (a) $ 9 $ 9 $ 13 $ 13 Liabilities: Long-term debt, including current portion (b) $ 6,023 $ 6,020 $ 6,066 $ 6,099 (a) Carrying amount as of December 31, 2017, includes the long-term portion of notes receivable, which is recorded in other noncurrent assets on the Company's consolidated balance sheets. (b) Excludes deferred financing costs, which are recorded as a reduction to long-term debt on the Company's consolidated balance sheets. The fair value of the Company's publicly-traded long-term debt is based on quoted market prices and is classified as Level 2 within the fair value hierarchy. The fair value of debt securities, non-publicly traded long-term debt and certain notes receivable of the Company are based on expected future cash flows discounted at market interest rates, or current interest rates for similar instruments with equivalent credit quality and are classified as Level 3 within the fair value hierarchy. The following table presents the level within the fair value hierarchy for long-term debt, including current portion as of March 31, 2018 , and December 31, 2017 : As of March 31, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 1,472 $ 4,548 $ 1,502 $ 4,597 Recurring Fair Value Measurements The Company records its derivative assets and liabilities at fair value on its consolidated balance sheet. The following table presents assets and liabilities measured and recorded at fair value on the Company's consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of March 31, 2018 As of December 31, 2017 Fair Value (a) Fair Value (a) (In millions) Level 2 Level 2 Derivative assets: Commodity contracts $ — $ 1 Interest rate contracts 17 1 Total assets 17 2 Derivative liabilities: Commodity contracts 2 1 Interest rate contracts 24 48 Total liabilities $ 26 $ 49 (a) There were no derivative assets or liabilities classified as Level 1 or Level 3 as of March 31, 2018 and December 31, 2017 . Derivative Fair Value Measurements The Company's contracts are non-exchange-traded and valued using prices provided by external sources. For the Company’s energy markets, management receives quotes from multiple sources. To the extent that multiple quotes are received, the prices reflect the average of the bid-ask mid-point prices obtained from all sources believed to provide the most liquid market for the commodity. The fair value of each contract is discounted using a risk free interest rate. In addition, a credit reserve is applied to reflect credit risk, which is, for interest rate swaps, calculated based on credit default swaps using the bilateral method. For commodities, to the extent that the net exposure under a specific master agreement is an asset, the Company uses the counterparty’s default swap rate. If the net exposure under a specific master agreement is a liability, the Company uses NRG's default swap rate. For interest rate swaps and commodities, the credit reserve is added to the discounted fair value to reflect the exit price that a market participant would be willing to receive to assume the liabilities or that a market participant would be willing to pay for the assets. As of March 31, 2018 , the credit reserve was less than $1 million . It is possible that future market prices could vary from those used in recording assets and liabilities and such variations could be material. Concentration of Credit Risk In addition to the credit risk discussion in Note 2 , Summary of Significant Accounting Policies , to the consolidated financial statements included in the Company's 2017 Form 10-K, the following is a discussion of the concentration of credit risk for the Company's financial instruments. 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. The Company monitors and manages credit risk through credit policies that include: (i) an established credit approval process; (ii) daily monitoring of counterparties' credit limits; (iii) the use of credit mitigation measures such as margin, collateral, prepayment arrangements, or volumetric limits; (iv) the use of payment netting agreements; and (v) the use of master netting agreements that allow for the netting of positive and negative exposures of various contracts associated with a single counterparty. Risks surrounding counterparty performance and credit could ultimately impact the amount and timing of expected cash flows. The Company seeks to mitigate counterparty risk by having a diversified portfolio of counterparties. Counterparty credit exposure includes credit risk exposure under certain long-term agreements, including solar and other PPAs. As external sources or observable market quotes are not available to estimate such exposure, the Company estimates the exposure related to 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, 2018 , credit risk exposure to these counterparties attributable to the Company's ownership interests was approximately $2.6 billion for the next five years . The majority of these power contracts are with utilities with strong credit quality and public utility commission or other regulatory support. However, such regulated utility counterparties can be impacted by changes in government regulations, which the Company is unable to predict.

Accounting for Derivative Instr

Accounting for Derivative Instruments and Hedging Activities	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Accounting for Derivative Instruments and Hedging Activities	Accounting for Derivative Instruments and Hedging Activities This footnote should be read in conjunction with the complete description under Note 7 , Accounting for Derivative Instruments and Hedging Activities , to the consolidated financial statements included in the Company's 2017 Form 10-K. Energy-Related Commodities As of March 31, 2018 , the Company had energy-related derivative instruments extending through 2020. At March 31, 2018 , these contracts were not designated as cash flow or fair value hedges. Interest Rate Swaps As of March 31, 2018 , the Company had interest rate derivative instruments on non-recourse debt extending through 2041, a portion of which are designated as cash flow hedges. Volumetric Underlying Derivative Transactions The following table summarizes the net notional volume buy of the Company's open derivative transactions broken out by commodity: Total Volume March 31, 2018 December 31, 2017 Commodity Units (In millions) Natural Gas MMBtu 1 2 Interest Dollars $ 2,001 $ 2,050 Fair Value of Derivative Instruments The following table summarizes the fair value within the derivative instrument valuation on the balance sheet: Fair Value Derivative Assets (a) Derivative Liabilities March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 (In millions) Derivatives Designated as Cash Flow Hedges: Interest rate contracts current $ 1 $ — $ 2 $ 4 Interest rate contracts long-term 7 1 6 9 Total Derivatives Designated as Cash Flow Hedges 8 1 8 13 Derivatives Not Designated as Cash Flow Hedges: Interest rate contracts current — — 6 13 Interest rate contracts long-term 9 — 10 22 Commodity contracts current — 1 1 1 Commodity contracts long-term — — 1 — Total Derivatives Not Designated as Cash Flow Hedges 9 1 18 36 Total Derivatives $ 17 $ 2 $ 26 $ 49 (a) Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of March 31, 2018 and December 31, 2017 . 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. As of March 31, 2018 , and December 31, 2017 , there was no outstanding collateral paid or received. The following tables summarize the offsetting of derivatives by the counterparty master agreement level as of March 31, 2018 , and December 31, 2017 : As of March 31, 2018 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts (a) : (In millions) Derivative assets $ — $ — $ — Derivative liabilities (2 ) — (2 ) Total commodity contracts (2 ) — (2 ) Interest rate contracts: Derivative assets 17 (2 ) 15 Derivative liabilities (24 ) 2 (22 ) Total interest rate contracts (7 ) — (7 ) Total derivative instruments $ (9 ) $ — $ (9 ) (a) There were no commodity contracts classified as derivative assets as of March 31, 2018 . As of December 31, 2017 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts: (In millions) Derivative assets $ 1 $ — $ 1 Derivative liabilities (1 ) — (1 ) Total commodity contracts — — — Interest rate contracts: Derivative assets 1 (1 ) — Derivative liabilities (48 ) 1 (47 ) Total interest rate contracts (47 ) — (47 ) Total derivative instruments $ (47 ) $ — $ (47 ) Accumulated Other Comprehensive Loss The following table summarizes the effects on the Company’s accumulated OCL balance attributable to interest rate swaps designated as cash flow hedge derivatives, net of tax: Three months ended March 31, 2018 2017 (In millions) Accumulated OCL beginning balance $ (60 ) $ (70 ) Reclassified from accumulated OCL to income due to realization of previously deferred amounts 4 4 Mark-to-market of cash flow hedge accounting contracts 13 2 Accumulated OCL ending balance, net of income tax benefit of $6 and $15, respectively (43 ) (64 ) Accumulated OCL attributable to noncontrolling interests (23 ) (39 ) Accumulated OCL attributable to NRG Yield, Inc. $ (20 ) $ (25 ) Losses expected to be realized from OCL during the next 12 months, net of income tax benefit of $1 $ 11 The Company's regression analysis for Marsh Landing, Walnut Creek and Avra Valley interest rate swaps, while positively correlated, no longer contain matching terms for cash flow hedge accounting. As a result, the Company voluntarily de-designated the Marsh Landing, Walnut Creek and Avra Valley cash flow hedges as of April 28, 2017, and will prospectively mark these derivatives to market through the income statement. Impact of Derivative Instruments on the Statements of Operations The Company has interest rate derivative instruments that are not designated as cash flow hedges. The effect of interest rate hedges is recorded to interest expense. For the three months ended March 31, 2018 and 2017 , the impact to the consolidated statements of operations was a gain of $24 million and $4 million , respectively. A portion of the Company’s derivative commodity contracts relates to its Thermal Business for the purchase of fuel commodities based on the forecasted usage of the thermal district energy centers. Realized gains and losses on these contracts are reflected in the fuel costs that are permitted to be billed to customers through the related customer contracts or tariffs and, accordingly, no gains or losses are reflected in the consolidated statements of income for these contracts. See Note 5 , Fair Value of Financial Instruments , for a discussion regarding concentration of credit risk.

Long-term Debt

Long-term Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-term Debt	Long-term Debt This footnote should be read in conjunction with the complete description under Note 10 , Long-term Debt , to the consolidated financial statements included in the Company's 2017 Form 10-K. Long-term debt consisted of the following: March 31, 2018 December 31, 2017 March 31, 2018, interest rate % (a) Letters of Credit Outstanding at March 31, 2018 (In millions, except rates) 2019 Convertible Notes $ 345 $ 345 3.500 2020 Convertible Notes 288 288 3.250 2024 Senior Notes 500 500 5.375 2026 Senior Notes 350 350 5.000 NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2019 (b) 75 55 L+2.500 $ 67 Project-level debt: Agua Caliente Borrower 2, due 2038 40 41 5.430 17 Alpine, due 2022 135 135 L+1.750 16 Alta Wind I - V lease financing arrangements, due 2034 and 2035 926 926 5.696 - 7.015 118 Buckthorn Solar, due 2018 and 2025 183 169 L + 1.750 10 CVSR, due 2037 731 746 2.339 - 3.775 — CVSR Holdco Notes, due 2037 188 194 4.680 13 El Segundo Energy Center, due 2023 369 400 L+1.75 - L+2.375 139 Energy Center Minneapolis, due 2025 83 83 5.950 — Energy Center Minneapolis Series D Notes, due 2031 125 125 3.550 — Laredo Ridge, due 2028 93 95 L+1.875 10 Marsh Landing, due 2023 309 318 L+2.125 38 Tapestry, due 2021 158 162 L+1.625 20 Utah Solar Portfolio, due 2022 278 278 various 13 Viento, due 2023 163 163 L+3.00 27 Walnut Creek, due 2023 259 267 L+1.625 65 Other 440 443 various 39 Subtotal project-level debt: 4,480 4,545 Total debt 6,038 6,083 Less current maturities (c) (698 ) (339 ) Less net debt issuance costs (64 ) (68 ) Less discounts (d) (15 ) (17 ) Total long-term debt $ 5,261 $ 5,659 (a) As of March 31, 2018 , L+ equals 3 month LIBOR plus x%, except for Viento, due 2023 where L+ equals 6 month LIBOR plus 3.00% and Buckthorn Solar and Utah Solar Portfolio, where L+ equals 1 month LIBOR plus x%. (b) Applicable rate is determined by the borrower leverage ratio, as defined in the credit agreement. (c) The 2019 Convertible Notes become due in February 2019 and are included in current portion of long-term debt on the Company's consolidated balance sheet as of March 31, 2018 . (d) Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes. The financing arrangements listed above contain certain covenants, including financial covenants that the Company is required to be in compliance with during the term of the respective arrangement. As of March 31, 2018 , the Company was in compliance with all of the required covenants. The discussion below describes material changes to or additions of long-term debt for the three months ended March 31, 2018 . NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility As of March 31, 2018 , the Company had outstanding borrowings of $75 million under the revolving credit facility, which included borrowings of $20 million made during the period ended March 31, 2018 , to finance the acquisition of the Buckthorn Solar Drop Down Asset, as well as for general corporate purposes. The Company also had $67 million of letters of credit outstanding. On February 6, 2018, NRG Yield Operating LLC and NRG Yield LLC amended the revolving credit facility to modify the "change of control" provisions to permit the consummation of the NRG Transaction, and also to permit NRG Yield Operating LLC, NRG Yield LLC and certain subsidiaries to incur up to $1.5 billion of unsecured indebtedness in order to repurchase or make other required cash payments, in each case if applicable, with respect to NRG Yield Operating LLC’s outstanding senior notes and NRG Yield's outstanding convertible notes in connection with the NRG Transaction. On April 30, 2018, the Company closed on the refinancing of the revolving credit facility, which extended the maturity of the facility to April 28, 2023, and decreased the Company's overall cost of borrowing from L+ 2.50% to L+ 1.75% . The facility will continue to be used for general corporate purposes including financing of future acquisitions and posting letters of credit. Project - level Debt Buckthorn Solar Drop Down Asset Debt As part of the Buckthorn Solar Drop Down Asset acquisition, the Company assumed non-recourse debt of $183 million relating to Buckthorn Portfolio Solar, LLC. The assumed debt consisted of a Construction Loan and an Investment Tax Credits, or ITC, Bridge Loan, both at an interest rate of LIBOR plus 1.75% . The Construction Loan will convert to a Term Loan with an expected maturity of May 2025, and the ITC Bridge Loan will be paid at substantial completion of the Buckthorn Solar project with the final proceeds from the TE Investor. Buckthorn Solar entered into a series of fixed for floating interest rate swaps that would fix the interest rate for a minimum of 80% of the outstanding notional amount. All interest rate swap payments by Buckthorn Solar and its counterparties are made quarterly and LIBOR is determined in advance of each interest period.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic earnings per common share is computed by dividing net income by the weighted average number of common shares outstanding. Shares issued during the year are weighted for the portion of the year that they were outstanding. Diluted earnings per share is computed in a manner consistent with that of basic earnings per share while giving effect to all potentially dilutive common shares that were outstanding during the period. The reconciliation of the Company's basic and diluted earnings per share is shown in the following tables: Three months ended March 31, 2018 2017 (In millions, except per share data) (a) Common Class A Common Class C Common Class A Common Class C Basic and diluted earnings (loss) per share attributable to NRG Yield, Inc. common stockholders Net income (loss) attributable to NRG Yield, Inc. $ 6 $ 10 $ (1 ) $ (2 ) Weighted average number of common shares outstanding — basic and diluted 35 65 35 63 Earnings (Loss) per weighted average common share — basic and diluted $ 0.16 $ 0.16 $ (0.03 ) $ (0.03 ) (a) Basic and diluted earnings (loss) per share might not recalculate due to presenting values in millions rather than whole dollars. The following table summarizes the Company's outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company's diluted earnings per share: Three months ended March 31, 2018 2017 (In millions of shares) 2019 Convertible Notes - Common Class A 15 15 2020 Convertible Notes - Common Class C 10 10

Changes in Capital Structure

Changes in Capital Structure	3 Months Ended
	Mar. 31, 2018
Changes in Capital Structure [Abstract]
Partners' Capital Notes Disclosure [Text Block]	Changes in Capital Structure At-the-Market Equity Offering Program, or the ATM Program NRG Yield, Inc. is party to an equity distribution agreement with Barclays Capital Inc., Credit Suisse Securities (USA) LLC, J.P. Morgan Securities LLC and RBC Capital Markets, LLC, as sales agents. Pursuant to the terms of the equity distribution agreement, NRG Yield, Inc. may offer and sell shares of its Class C common stock par value $0.01 per share, from time to time through the sales agents up to an aggregate sales price of $150 million through an at-the-market equity offering program, or the ATM Program. NRG Yield, Inc. may also sell shares of its Class C common stock to any of the sales agents, as principals for its own account, at a price agreed upon at the time of sale. The Company sold a total of 936,662 of Class C common stock for net proceeds of $16 million during the period ended March 31, 2018, $6 million of which were received in the second quarter of 2018. The Company incurred commission fees of $105 thousand during the period ended March 31, 2018. As of April 3, 2018, approximately $99 million of Class C common stock remains available for issuance under the ATM Program. As a result of the Company's sale of shares of Class C common stock under the ATM Program, the public shareholders of Class A and Class C common stock increased their economic and voting interests in NRG Yield, Inc. to 53.9% , and 44.9% , respectively, as of March 31, 2018 . Dividends to Class A and Class C common stockholders The following table lists the dividends paid on the Company's Class A common stock and Class C common stock during the three months ended March 31, 2018 : First Quarter 2018 Dividends per Class A share $ 0.298 Dividends per Class C share $ 0.298 Dividends on the Class A common stock and Class C common stock are subject to available capital, market conditions, and compliance with associated laws, regulations and other contractual obligations. The Company expects that, based on current circumstances, comparable cash dividends will continue to be paid in the foreseeable future. On April 24, 2018 , the Company declared quarterly dividends on its Class A common stock and Class C common stock of $0.309 per share payable on June 15, 2018 , to stockholders of record as of June 1, 2018 . The Company also has authorized 10 million shares of preferred stock, par value $0.01 per share. None of the shares of preferred stock have been issued.

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company’s segment structure reflects how management currently operates and allocates resources. The Company's businesses are segregated based on conventional power generation, renewable businesses which consist of solar and wind, and the thermal and chilled water business. The Corporate segment reflects the Company's corporate costs. The Company's chief operating decision maker, its Chief Executive Officer, evaluates the performance of its segments based on operational measures including adjusted earnings before interest, taxes, depreciation and amortization, or Adjusted EBITDA, and CAFD, as well as economic gross margin and net income (loss). Three months ended March 31, 2018 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 79 $ 98 $ 48 $ — $ 225 Cost of operations 22 34 33 — 89 Depreciation and amortization 26 50 5 — 81 General and administrative — — — 5 5 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 31 14 10 (6 ) 49 Equity in earnings of unconsolidated affiliates 3 1 — — 4 Other income, net — 1 — — 1 Interest expense (7 ) (24 ) (2 ) (22 ) (55 ) Income (loss) before income taxes 27 (8 ) 8 (28 ) (1 ) Income tax benefit — — — (1 ) (1 ) Net Income (Loss) $ 27 $ (8 ) $ 8 $ (27 ) $ — Total Assets $ 1,815 $ 5,953 $ 424 $ 170 $ 8,362 Three months ended March 31, 2017 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 75 $ 102 $ 44 $ — $ 221 Cost of operations 22 33 30 — 85 Depreciation and amortization 24 48 5 — 77 General and administrative — — — 4 4 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 29 21 9 (5 ) 54 Equity in earnings of unconsolidated affiliates 3 16 — — 19 Other income, net — 1 — — 1 Loss on debt extinguishment — (2 ) — — (2 ) Interest expense (12 ) (39 ) (3 ) (21 ) (75 ) Income (loss) before income taxes 20 (3 ) 6 (26 ) (3 ) Income tax benefit — — — (1 ) (1 ) Net Income (Loss) $ 20 $ (3 ) $ 6 $ (25 ) $ (2 )

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Effective Tax Rate The income tax provision consisted of the following: Three months ended March 31, 2018 2017 (In millions, except percentages) Loss before income taxes $ (1 ) $ (3 ) Income tax benefit (1 ) (1 ) Effective income tax rate 100.0 % 33.3 % For the three months ended March 31, 2018 and 2017 , the overall effective tax rate was different than the statutory rate of 21% and 35% , respectively, primarily due to production and investment tax credits generated from certain wind and solar assets, respectively, and earnings allocated to NRG resulting from its interest in NRG Yield LLC. For tax purposes, NRG Yield LLC is treated as a partnership; therefore, the Company and NRG each record their respective share of taxable income or loss.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions Disclosure	Related Party Transactions In addition to the transactions and relationships described elsewhere in the notes to the consolidated financial statements, NRG or certain subsidiaries of NRG provide services to the Company's project entities. Amounts due to NRG or its subsidiaries are recorded as accounts payable - affiliate and amounts due to the Company from NRG subsidiaries are recorded as accounts receivable - affiliate on the Company's consolidated balance sheet. The disclosures below summarize the Company's material related party transactions with NRG and its subsidiaries that are included in the Company's operating revenues and operating costs. Power Purchase Agreements (PPAs) between the Company and NRG Power Marketing Elbow Creek and Dover are parties to PPAs with NRG Power Marketing and generate revenue under the PPAs, which are recorded to operating revenues in the Company's consolidated statements of operations. For the three months ended March 31, 2018 and 2017 , Elbow Creek and Dover, collectively, generated revenues of $3 million and $4 million , respectively. Energy Marketing Services Agreement by and between Thermal entities and NRG Power Marketing NRG Energy Center Dover LLC, NRG Energy Center Minneapolis, NRG Energy Center Phoenix LLC, and NRG Energy Center Paxton LLC, or Thermal entities, which are subsidiaries of the Company, are parties to Energy Marketing Services Agreements with NRG Power Marketing, a wholly-owned subsidiary of NRG. Under the agreements, NRG Power Marketing procures fuel and fuel transportation for the operation of the Thermal entities. For each of the three months ended March 31, 2018 and 2017 , the Thermal entities purchased $4 million of natural gas from NRG Power Marketing. Operation and Maintenance (O&M) Services Agreements by and between the Company's subsidiaries and NRG Certain of the Company's subsidiaries are party to O&M Services Agreements with NRG, pursuant to which NRG subsidiaries provide necessary and appropriate services to operate and maintain the subsidiaries' plant operations, businesses and thermal facilities. NRG is reimbursed for the provided services, as well as for all reasonable and related expenses and expenditures, and payments to third parties for services and materials rendered to or on behalf of the parties to the agreements. NRG is not entitled to any management fee or mark-up under the agreements. The fees incurred under these agreements were $10 million for each of the three months ended March 31, 2018 and 2017 . The Company had $9 million and $13 million due to NRG for the services performed under the O&M Agreements in accounts payable — affiliate as of March 31, 2018 and December 31, 2017 , respectively. O&M Services Agreements by and between GenConn and NRG GenConn incurs fees under two O&M agreements with wholly-owned subsidiaries of NRG. For the three months ended March 31, 2018 and 2017 , the aggregate fees incurred under the agreements were $1 million for each period. Administrative Services Agreement by and between Marsh Landing and NRG West Coast LLC Marsh Landing is a party to an administrative services agreement with NRG West Coast LLC, a wholly owned subsidiary of NRG. The Company reimbursed costs under this agreement of $3 million for each of the three months ended March 31, 2018 and 2017 . There was a balance of $3 million and $1 million due to NRG West Coast LLC in accounts payable—affiliate as of March 31, 2018 and December 31, 2017 , respectively. Administrative Services Agreements by and between the Company and NRG Renew Operation & Maintenance LLC Various wholly-owned subsidiaries of the Company in the Renewables segment are party to administrative services agreements with NRG Renew Operation & Maintenance LLC, or RENOM, a wholly-owned subsidiary of NRG, which provides O&M services to these subsidiaries. The Company incurred total expenses for these services of $7 million and $6 million for the three months ended March 31, 2018 and 2017 , respectively. There was a balance of $4 million and $5 million due to RENOM as of March 31, 2018 and December 31, 2017 , respectively. Management Services Agreement by and between the Company and NRG NRG provides the Company with various operational, management, and administrative services, which include human resources, accounting, tax, legal, information systems, treasury, and risk management, as set forth in the Management Services Agreement. As of March 31, 2018 , the base management fee was approximately $9 million per year, subject to an inflation-based adjustment annually at an inflation factor based on the year-over-year U.S. consumer price index. The fee is also subject to adjustments following the consummation of future acquisitions and as a result of a change in the scope of services provided under the Management Services Agreement. Costs incurred under this agreement for each of the three months ended March 31, 2018 and 2017 were $2 million . The costs incurred under the Management Service Agreement included certain direct expenses incurred by NRG on behalf of the Company in addition to the base management fee. EPC Agreement by and between NECP and NRG On October 31, 2016, NRG Business Services LLC, a subsidiary of NRG, and NECP, a wholly owned subsidiary of the Company, entered into an EPC agreement for the construction of a 73 MWt district energy system for NECP to provide 150 kpph of steam, 6,750 tons of chilled water and 7.5 MW of emergency backup power service to UPMC Mercy. The initial term of the energy services agreement with UPMC Mercy will be for a period of twenty years from the service commencement date. Pursuant to the terms of the EPC agreement and amendments made through the end of 2017, NECP agreed to pay NRG Business Services LLC $88 million , subject to adjustment based upon certain conditions in the EPC agreement, upon substantial completion of the project. In addition, the capacity of the district energy system increased from 73 MWt to 80 MWt. The project is expected to reach commercial operations in the second quarter of 2018.

Contingencies (Notes)

Contingencies (Notes)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies Disclosure [Text Block]	Contingencies This note should be read in conjunction with the complete description under Note 16 , Commitments and Contingencies , to the Company's 2017 Form 10-K. 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. The Company records reserves for estimated losses from contingencies when information available indicates that a loss is probable and the amount of the loss, or range of loss, can be reasonably estimated. As applicable, the Company has established an adequate reserve for the matters discussed below. In addition, legal costs are expensed as incurred. Management assesses such matters based on current information and makes a judgment concerning its potential outcome, considering the nature of the claim, the amount and nature of damages sought, and the probability of success. The Company is unable to predict the outcome of the legal proceedings below 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, the Company 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 the Company's consolidated financial position, results of operations, or cash flows. Braun v. NRG Yield, Inc. — On April 19, 2016, plaintiffs filed a putative class action lawsuit against NRG Yield, Inc., the current and former members of its board of directors individually, and other parties in California Superior Court in Kern County, CA. Plaintiffs allege various violations of the Securities Act due to the defendants’ alleged failure to disclose material facts related to low wind production prior to the NRG Yield, Inc.'s June 22, 2015 Class C common stock offering. Plaintiffs seek compensatory damages, rescission, attorney’s fees and costs. The Defendants filed demurrers and a motion challenging jurisdiction on October 18, 2016. The case is currently stayed by agreement of the parties. On May 2, 2018, the court approved a joint stipulation which provides: (i) plaintiffs' opposition brief is due on or before July 30, 2018; (ii) defendants' reply brief is due on or before October 5, 2018; and (iii) a hearing on the motions is scheduled on October 30, 2018. GenOn Noteholders' Lawsuit — On December 13, 2016, certain indenture trustees for an ad hoc group of holders, or the Noteholders, of the GenOn Energy, Inc., or GenOn, 7.875% Senior Notes due 2017, 9.500% Notes due 2018, and 9.875% Notes due 2020, and the GenOn Americas Generation, LLC 8.50% Senior Notes due 2021 and 9.125% Senior Notes due 2031, along with certain of the Noteholders, filed a complaint in the Superior Court of the State of Delaware against NRG and GenOn alleging certain claims related to the Services Agreement between NRG and GenOn. On April 30, 2017, the Noteholders filed an amended complaint that asserts additional claims of fraudulent transfer, insider preference and breach of fiduciary duties. In addition to NRG and GenOn, the amended complaint names NRG Yield LLC and certain current and former officers and directors of GenOn as defendants. The plaintiffs, among other things, generally seek return of all monies paid under the Services Agreement and any other damages that the court deems appropriate. On April 28, 2017, the bondholders filed an amended complaint adding the GenOn directors and officers as defendants and asserting claims that they breached certain fiduciary duties. Plaintiffs specifically allege that the transfer of Marsh Landing to NRG Yield LLC constituted a fraudulent transfer. On June 12, 2017, certain GenOn entities, NRG and certain holders of the GenOn and GenOn Americas Generation, LLC senior notes entered into a restructuring support and lock-up agreement. On December 14, 2017, a settlement agreement was entered into between GenOn and NRG which should ultimately resolve this lawsuit.

Summary of Significant Accoun21

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Revenue Recognition, Policy [Policy Text Block]	Revenue Recognition Revenue from Contracts with Customers On January 1, 2018, the Company adopted the guidance in ASC 606, Revenue from Contracts with Customers, or Topic 606, using the modified retrospective method applied to contracts which were not completed as of the adoption date, with no adjustment required to the financial statements upon adoption. Following the adoption of the new standard, the Company’s revenue recognition of its contracts with customers remains materially consistent with its historical practice. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company's policies with respect to its various revenue streams are detailed below. In general, the Company applies the invoicing practical expedient to recognize revenue for the revenue streams detailed below, except in circumstances where the invoiced amount does not represent the value transferred to the customer. Thermal Revenues Steam and chilled water revenue is recognized as the Company transfers the product to the customer, based on customer usage as determined by meter readings taken at month-end. Some locations read customer meters throughout the month, and recognize estimated revenue for the period between meter read date and month-end. For thermal contracts, the Company’s performance obligation to deliver steam and chilled water is satisfied over time and revenue is recognized based on the invoiced amount. The Thermal Business subsidiaries collect and remit state and local taxes associated with sales to their customers, as required by governmental authorities. These taxes are presented on a net basis in the income statement. As contracts for steam and chilled water are long-term contracts, the Company has performance obligations under these contracts that have not yet been satisfied. These performance obligations have transaction prices that are both fixed and variable, and that vary based on the contract duration, customer type, inception date and other contract-specific factors. For the fixed price contracts, the Company cannot accurately estimate the amount of its unsatisfied performance obligations as it will vary based on customer usage, which will depend on factors such as weather and customer activity. Power Purchase Agreements, or PPAs The majority of the Company’s revenues are obtained through PPAs or other contractual agreements. Energy, capacity and where applicable, renewable attributes, from the majority of the Company’s renewable energy assets and certain conventional energy plants is sold through long-term PPAs and tolling agreements to a single counterparty, which is often a utility or commercial customer. The majority of these PPAs are accounted for as leases. ASC 840 requires the minimum lease payments received to be amortized over the term of the lease and contingent rentals are recorded when the achievement of the contingency becomes probable. Judgment is required by management in determining the economic life of each generating facility, in evaluating whether certain lease provisions constitute minimum payments or represent contingent rent and other factors in determining whether a contract contains a lease and whether the lease is an operating lease or capital lease. Renewable Energy Credits As stated above, renewable energy credits, or RECs, are usually sold through long-term PPAs. Revenue from the sale of self-generated RECs is recognized when related energy is generated and simultaneously delivered even in cases where there is a certification lag as it has been deemed to be perfunctory. In a bundled contract to sell energy, capacity and/or self-generated RECs, all performance obligations are deemed to be delivered at the same time and hence, timing of recognition of revenue for all performance obligations is the same and occurs over time. In such cases, it is often unnecessary to allocate transaction price to multiple performance obligations. Sale of Emission Allowances The Company records its bank of emission allowances as part of intangible assets. From time to time, management may authorize the transfer of emission allowances in excess of usage from the Company's emission bank to intangible assets held-for-sale for trading purposes. The Company records the sale of emission allowances on a net basis within operating revenue in the Company's consolidated statements of operations. Disaggregated Revenues The following table represents the Company’s disaggregation of revenue from contracts with customers for the three months ended March 31, 2018 along with the reportable segment for each category: (In millions) Conventional Generation Renewables Thermal Total Energy revenue (a) $ 1 $ 112 $ 1 $ 114 Capacity revenue (a) 79 — 3 82 Contract amortization (1 ) (15 ) (1 ) (17 ) Other revenue — 1 45 46 Total operating revenue 79 98 48 225 Less: Lease revenue (80 ) (101 ) — (181 ) Less: Contract amortization 1 15 1 17 Total revenue from contracts with customers $ — $ 12 $ 49 $ 61 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 1 $ 101 $ — $ 102 Capacity Revenue 79 — — 79 Contract Amortization Assets and liabilities recognized from power sales agreements assumed through acquisitions related to the sale of electric capacity and energy in future periods for which the fair value has been determined to be significantly less (more) than market are amortized to revenue over the term of each underlying contract based on actual generation and/or contracted volumes or on a straight-line basis, where applicable. Contract Balances The following table reflects the contract assets and liabilities included on the Company’s balance sheet as of March 31, 2018: (In millions) March 31, 2018 Accounts receivable, net - Contracts with customers $ 26 Accounts receivable, net - Leases 56 Total accounts receivable, net $ 82
Income Tax, Policy [Policy Text Block]	Income Taxes NRG Yield, Inc. is included in certain NRG consolidated unitary state tax return filings which is reflected in NRG Yield, Inc.'s state effective tax rate. If NRG Yield, Inc. filed under a separate standalone methodology, there would be no material change to the state tax benefit as of March 31, 2018 .
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions. These estimates and assumptions impact the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities as of the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could be different from these estimates.
Noncontrolling Interest Disclosure [Text Block]	Noncontrolling Interests Stockholders' equity represents the equity associated with the Class A and Class C common stockholders, the equity associated with the Class B and Class D common stockholder, NRG, and the third-party interests under certain tax equity arrangements are classified as noncontrolling interests. The following table reflects the changes in the Company's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 as previously reported $ 391 Net Assets of Buckthorn Solar Drop Down Asset as of December 31, 2017 21 Balance as of December 31, 2017 as recast $ 412 Capital contributions from tax equity investors, net of distributions 30 Payment for the Buckthorn Solar Drop Down Asset (42 ) Pre-acquisition net income of the Buckthorn Solar Drop Down Asset 4 Comprehensive loss (11 ) Distributions to NRG, net (22 ) Balance as of March 31, 2018 $ 371 NRG Yield LLC Distributions to NRG The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the three months ended March 31, 2018 : First Quarter 2018 Distributions per Class B Unit $ 0.298 Distributions per Class D Unit $ 0.298 On April 24, 2018 , NRG Yield LLC declared a distribution on its Class A, Class B, Class C and Class D units of $0.309 per unit payable on June 15, 2018 to unit holders of record as of June 1, 2018 .
Distributions [Policy Text Block]	NRG Yield LLC Distributions to NRG The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the three months ended March 31, 2018 : First Quarter 2018 Distributions per Class B Unit $ 0.298 Distributions per Class D Unit $ 0.298 On April 24, 2018 , NRG Yield LLC declared a distribution on its Class A, Class B, Class C and Class D units of $0.309 per unit payable on June 15, 2018 to unit holders of record as of June 1, 2018
Recent Accounting Developments	Recent Accounting Developments - Not Yet Adopted ASU 2016-02 — In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), or Topic 842, with the objective to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and to improve financial reporting by expanding the related disclosures. The guidance in Topic 842 provides that a lessee that may have previously accounted for a lease as an operating lease under current GAAP should recognize the assets and liabilities that arise from a lease on the balance sheet. In addition, Topic 842 expands the required quantitative and qualitative disclosures with regards to lease arrangements. The Company will adopt the standard effective January 1, 2019 and expects to elect certain of the practical expedients permitted, including the expedient that permits the Company to retain its existing lease assessment and classification. The Company is currently working through an adoption plan and evaluating the anticipated impact on the Company's results of operations, cash flows and financial position. While the Company is currently evaluating the impact the new guidance will have on its financial position and results of operations, the Company expects to recognize lease liabilities and right of use assets. The extent of the increase to assets and liabilities associated with these amounts remains to be determined pending the Company’s review of its existing lease contracts and service contracts which may contain embedded leases. While this review is still in process, the Company believes the adoption of Topic 842 may be material to its financial statements. The Company is continuing to monitor potential changes to Topic 842 that have been proposed by the FASB and will assess any necessary changes to the implementation as the guidance is updated.

Segment Reporting Segment Repor

Segment Reporting Segment Reporting (Policies)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Segment Reporting, Policy [Policy Text Block]	The Company’s segment structure reflects how management currently operates and allocates resources. The Company's businesses are segregated based on conventional power generation, renewable businesses which consist of solar and wind, and the thermal and chilled water business. The Corporate segment reflects the Company's corporate costs. The Company's chief operating decision maker, its Chief Executive Officer, evaluates the performance of its segments based on operational measures including adjusted earnings before interest, taxes, depreciation and amortization, or Adjusted EBITDA, and CAFD, as well as economic gross margin and net income (loss).

Nature of Business Nature of Bu

Nature of Business Nature of Business (Tables)	3 Months Ended
	Mar. 31, 2018
Nature of Business Disclosure [Abstract]
IPO of NRG Yield	The following table represents the structure of the Company as of March 31, 2018 :
Schedule of Ownership	As of March 31, 2018 , the Company's operating assets are comprised of the following projects: Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Conventional El Segundo 100 % 550 Southern California Edison 2023 GenConn Devon 50 % 95 Connecticut Light & Power 2040 GenConn Middletown 50 % 95 Connecticut Light & Power 2041 Marsh Landing 100 % 720 Pacific Gas and Electric 2023 Walnut Creek 100 % 485 Southern California Edison 2023 1,945 Utility Scale Solar Agua Caliente 16 % 46 Pacific Gas and Electric 2039 Alpine 100 % 66 Pacific Gas and Electric 2033 Avenal 50 % 23 Pacific Gas and Electric 2031 Avra Valley 100 % 26 Tucson Electric Power 2032 Blythe 100 % 21 Southern California Edison 2029 Borrego 100 % 26 San Diego Gas and Electric 2038 CVSR 100 % 250 Pacific Gas and Electric 2038 Desert Sunlight 250 25 % 63 Southern California Edison 2035 Desert Sunlight 300 25 % 75 Pacific Gas and Electric 2040 Kansas South 100 % 20 Pacific Gas and Electric 2033 Roadrunner 100 % 20 El Paso Electric 2031 TA High Desert 100 % 20 Southern California Edison 2033 Utah Solar Portfolio (b) (e) 50 % 265 PacifiCorp 2036 921 Distributed Solar Apple I LLC Projects 100 % 9 Various 2032 AZ DG Solar Projects 100 % 5 Various 2025 - 2033 SPP Projects 100 % 25 Various 2026 - 2037 Other DG Projects 100 % 13 Various 2023 - 2039 52 Wind Alta I 100 % 150 Southern California Edison 2035 Alta II 100 % 150 Southern California Edison 2035 Alta III 100 % 150 Southern California Edison 2035 Alta IV 100 % 102 Southern California Edison 2035 Alta V 100 % 168 Southern California Edison 2035 Alta X (b) 100 % 137 Southern California Edison 2038 Alta XI (b) 100 % 90 Southern California Edison 2038 Buffalo Bear 100 % 19 Western Farmers Electric Co-operative 2033 Crosswinds (b) (f) 99 % 21 Corn Belt Power Cooperative 2027 Elbow Creek (b) (f) 100 % 122 NRG Power Marketing LLC 2022 Elkhorn Ridge (b) (f) 66.7 % 54 Nebraska Public Power District 2029 Forward (b) (f) 100 % 29 Constellation NewEnergy, Inc. 2017 Goat Wind (b) (f) 100 % 150 Dow Pipeline Company 2025 Projects Percentage Ownership Net Capacity (MW) (a) Offtake Counterparty Expiration Hardin (b) (f) 99 % 15 Interstate Power and Light Company 2027 Laredo Ridge 100 % 80 Nebraska Public Power District 2031 Lookout (b) (f) 100 % 38 Southern Maryland Electric Cooperative 2030 Odin (b) (f) 99.9 % 20 Missouri River Energy Services 2028 Pinnacle 100 % 55 Maryland Department of General Services and University System of Maryland 2031 San Juan Mesa (b) (f) 75 % 90 Southwestern Public Service Company 2025 Sleeping Bear (b) (f) 100 % 95 Public Service Company of Oklahoma 2032 South Trent 100 % 101 AEP Energy Partners 2029 Spanish Fork (b) (f) 100 % 19 PacifiCorp 2028 Spring Canyon II (b) 90.1 % 29 Platte River Power Authority 2039 Spring Canyon III (b) 90.1 % 25 Platte River Power Authority 2039 Taloga 100 % 130 Oklahoma Gas & Electric 2031 Wildorado (b) (f) 100 % 161 Southwestern Public Service Company 2027 2,200 Thermal NRG Energy Center Dover LLC 100 % 103 NRG Power Marketing LLC 2018 Thermal generation 100 % 20 Various Various 123 Total net generation capacity (c) 5,241 Thermal equivalent MWt (d) 100 % 1,319 Various Various (a) Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018 . (b) Projects are part of tax equity arrangements. (c) The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs. (d) For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers. (e) Represents interests in Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC, all acquired as part of the March 2017 Drop Down Assets (ownership percentage is based upon cash to be distributed). (f) Projects are part of NRG Wind TE Holdco portfolio.

Summary of Significant Accoun24

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Schedule of Accumulated Depreciation and Amortization [Table Text Block]	The following table presents the accumulated depreciation included in the property, plant and equipment, net, and accumulated amortization included in intangible assets, net, respectively, as of March 31, 2018 and December 31, 2017 : March 31, 2018 December 31, 2017 (In millions) Property, Plant and Equipment Accumulated Depreciation $ 1,358 $ 1,285 Intangible Assets Accumulated Amortization 255 237
Schedule of Change in Noncontrolling Interest [Table Text Block]	The following table reflects the changes in the Company's noncontrolling interest balance: (In millions) Balance as of December 31, 2017 as previously reported $ 391 Net Assets of Buckthorn Solar Drop Down Asset as of December 31, 2017 21 Balance as of December 31, 2017 as recast $ 412 Capital contributions from tax equity investors, net of distributions 30 Payment for the Buckthorn Solar Drop Down Asset (42 ) Pre-acquisition net income of the Buckthorn Solar Drop Down Asset 4 Comprehensive loss (11 ) Distributions to NRG, net (22 ) Balance as of March 31, 2018 $ 371
Distributions Made to Limited Liability Company (LLC) Member, by Distribution [Table Text Block]	The following table lists the distributions paid to NRG on NRG Yield LLC's Class B and D units during the three months ended March 31, 2018 : First Quarter 2018 Distributions per Class B Unit $ 0.298 Distributions per Class D Unit $ 0.298
Disaggregation of Revenue [Table Text Block]	The following table represents the Company’s disaggregation of revenue from contracts with customers for the three months ended March 31, 2018 along with the reportable segment for each category: (In millions) Conventional Generation Renewables Thermal Total Energy revenue (a) $ 1 $ 112 $ 1 $ 114 Capacity revenue (a) 79 — 3 82 Contract amortization (1 ) (15 ) (1 ) (17 ) Other revenue — 1 45 46 Total operating revenue 79 98 48 225 Less: Lease revenue (80 ) (101 ) — (181 ) Less: Contract amortization 1 15 1 17 Total revenue from contracts with customers $ — $ 12 $ 49 $ 61 (a) The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840: Conventional Generation Renewables Thermal Total Energy Revenue $ 1 $ 101 $ — $ 102 Capacity Revenue 79 — — 79
Contract with Customer, Asset and Liability [Table Text Block]	The following table reflects the contract assets and liabilities included on the Company’s balance sheet as of March 31, 2018: (In millions) March 31, 2018 Accounts receivable, net - Contracts with customers $ 26 Accounts receivable, net - Leases 56 Total accounts receivable, net $ 82

Business Acquisitions Busines25

Business Acquisitions Business Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2018
November 2017 Drop Down Assets and August 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information [Table Text Block]	The following tables present a summary of the Company's historical information combining the financial information for the November 2017 Drop Down Assets and August 2017 Drop Down Assets transferred in connection with the acquisition: Three months ended March 31, 2017 As Previously Reported (a) November 2017 Drop Down Assets August 2017 Drop Down Assets As Currently Reported (In millions) Total operating revenues $ 218 $ 3 $ — $ 221 Operating income 54 — — 54 Net loss (1 ) (1 ) — (2 ) Less: Pre-acquisition net income of Drop Down Assets 12 (1 ) 2 13 Less: Loss attributable to noncontrolling interests (10 ) — (2 ) (12 ) Net loss attributable to NRG Yield, Inc. (3 ) — — (3 ) (a) As previously reported in the Company's Form 10-Q for the quarter ended March 31, 2017
Buckthorn Solar Drop Down Asset [Member]
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following is a summary of net assets transferred in connection with the acquisition of the Buckthorn Solar Drop Down Asset as of March 31, 2018: (In millions) Assets: Current assets $ 20 Property, plant and equipment 212 Non-current assets 3 Total assets 235 Liabilities: Debt (Current and non-current) (a) 176 Other current and non-current liabilities 15 Total liabilities 191 Less: noncontrolling interest 19 Net assets acquired $ 25 (a) Net of $7 million of net debt issuance costs.
Business Acquisition, Pro Forma Information [Table Text Block]	The following table presents the historical information summary combining the financial information for the Buckthorn Drop Down Asset transferred in connection with the acquisition: As of December 31, 2017 (In millions) As Previously Reported Buckthorn Solar Drop Down Asset As Currently Reported Assets: Current assets $ 482 $ — $ 482 Property, plant and equipment 5,204 206 5,410 Non-current assets 2,597 — 2,597 Total assets 8,283 206 8,489 Liabilities: Debt 5,837 161 5,998 Other current and non-current liabilities 308 24 332 Total liabilities 6,145 185 6,330 Net assets $ 2,138 $ 21 $ 2,159

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	3 Months Ended
	Mar. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity Method Investments [Table Text Block]	The following tables present summarized financial information for the Company's significant equity method investments: Three months ended March 31, (In millions) 2018 2017 Income Statement Data: DGPV entities (a) Operating revenues $ 11 $ 5 Operating loss — (1 ) Net income (loss) 3 (2 ) March 31, 2018 December 31, 2017 Balance Sheet Data: (In millions) DGPV entities (a) Current assets $ 92 $ 74 Non-current assets 718 671 Current liabilities 84 83 Non-current liabilities 236 216 Redeemable noncontrolling interest 42 44
Entities that are not consolidated [Member]
Schedule of Equity Method Investments [Line Items]
Schedule of Variable Interest Entities [Table Text Block]	The Company's maximum exposure to loss as of March 31, 2018 is limited to its equity investment in the unconsolidated entities, as further summarized in the table below: (In millions) Maximum exposure to loss Four Brothers Solar, LLC $ 209 GenConn Energy LLC 100 Granite Mountain Holdings, LLC 76 NRG DGPV Holdco 1 LLC 73 NRG DGPV Holdco 3 LLC 62 NRG DGPV Holdco 2 LLC 61 Iron Springs Holdings, LLC 53 NRG RPV Holdco 1 LLC 52
Consolidated Entities [Member]
Schedule of Equity Method Investments [Line Items]
Schedule of Variable Interest Entities [Table Text Block]	Summarized financial information for the Company's consolidated VIEs consisted of the following as of March 31, 2018 : (In millions) NRG Wind TE Holdco Alta Wind TE Holdco Spring Canyon Buckthorn Renewables, LLC Other current and non-current assets $ 172 $ 18 $ 2 $ 23 Property, plant and equipment 369 430 94 212 Intangible assets 2 259 — — Total assets 543 707 96 235 Current and non-current liabilities 195 8 5 191 Total liabilities 195 8 5 191 Noncontrolling interest 9 77 50 19 Net assets less noncontrolling interests $ 339 $ 622 $ 41 $ 25

Fair Value of Financial Instr27

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Estimated carrying values and fair values	The estimated carrying amounts and fair values of the Company’s recorded financial instruments not carried at fair market value are as follows: As of March 31, 2018 As of December 31, 2017 Carrying Amount Fair Value Carrying Amount Fair Value (In millions) Assets: Notes receivable (a) $ 9 $ 9 $ 13 $ 13 Liabilities: Long-term debt, including current portion (b) $ 6,023 $ 6,020 $ 6,066 $ 6,099
Fair Value, Option, Quantitative Disclosures [Table Text Block]	The fair value of the Company's publicly-traded long-term debt is based on quoted market prices and is classified as Level 2 within the fair value hierarchy. The fair value of debt securities, non-publicly traded long-term debt and certain notes receivable of the Company are based on expected future cash flows discounted at market interest rates, or current interest rates for similar instruments with equivalent credit quality and are classified as Level 3 within the fair value hierarchy. The following table presents the level within the fair value hierarchy for long-term debt, including current portion as of March 31, 2018 , and December 31, 2017 : As of March 31, 2018 As of December 31, 2017 Level 2 Level 3 Level 2 Level 3 (In millions) Long-term debt, including current portion $ 1,472 $ 4,548 $ 1,502 $ 4,597
Schedule of Fair Value, Assets and Liabilities [Table Text Block]	The Company records its derivative assets and liabilities at fair value on its consolidated balance sheet. The following table presents assets and liabilities measured and recorded at fair value on the Company's consolidated balance sheets on a recurring basis and their level within the fair value hierarchy: As of March 31, 2018 As of December 31, 2017 Fair Value (a) Fair Value (a) (In millions) Level 2 Level 2 Derivative assets: Commodity contracts $ — $ 1 Interest rate contracts 17 1 Total assets 17 2 Derivative liabilities: Commodity contracts 2 1 Interest rate contracts 24 48 Total liabilities $ 26 $ 49 (a) There were no derivative assets or liabilities classified as Level 1 or Level 3 as of March 31, 2018 and December 31, 2017 .

Accounting for Derivative Ins28

Accounting for Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net notional volume buy/(sell) of NRG Yield's open derivative transactions broken out by commodity	The following table summarizes the net notional volume buy of the Company's open derivative transactions broken out by commodity: Total Volume March 31, 2018 December 31, 2017 Commodity Units (In millions) Natural Gas MMBtu 1 2 Interest Dollars $ 2,001 $ 2,050
Fair value within the derivative instrument valuation on the balance sheets	he following table summarizes the fair value within the derivative instrument valuation on the balance sheet: Fair Value Derivative Assets (a) Derivative Liabilities March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 (In millions) Derivatives Designated as Cash Flow Hedges: Interest rate contracts current $ 1 $ — $ 2 $ 4 Interest rate contracts long-term 7 1 6 9 Total Derivatives Designated as Cash Flow Hedges 8 1 8 13 Derivatives Not Designated as Cash Flow Hedges: Interest rate contracts current — — 6 13 Interest rate contracts long-term 9 — 10 22 Commodity contracts current — 1 1 1 Commodity contracts long-term — — 1 — Total Derivatives Not Designated as Cash Flow Hedges 9 1 18 36 Total Derivatives $ 17 $ 2 $ 26 $ 49 (a) Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of March 31, 2018 and December 31, 2017 .
Offsetting of derivatives by counterparty master agreement level and collateral received or paid	The following tables summarize the offsetting of derivatives by the counterparty master agreement level as of March 31, 2018 , and December 31, 2017 : As of March 31, 2018 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts (a) : (In millions) Derivative assets $ — $ — $ — Derivative liabilities (2 ) — (2 ) Total commodity contracts (2 ) — (2 ) Interest rate contracts: Derivative assets 17 (2 ) 15 Derivative liabilities (24 ) 2 (22 ) Total interest rate contracts (7 ) — (7 ) Total derivative instruments $ (9 ) $ — $ (9 ) (a) There were no commodity contracts classified as derivative assets as of March 31, 2018 . As of December 31, 2017 Gross Amounts of Recognized Assets/Liabilities Derivative Instruments Net Amount Commodity contracts: (In millions) Derivative assets $ 1 $ — $ 1 Derivative liabilities (1 ) — (1 ) Total commodity contracts — — — Interest rate contracts: Derivative assets 1 (1 ) — Derivative liabilities (48 ) 1 (47 ) Total interest rate contracts (47 ) — (47 ) Total derivative instruments $ (47 ) $ — $ (47 )
Effects of NRG Yield's accumulated OCI balance attributable to interest rate swaps designated as cash flow hedge derivatives, net of tax	The following table summarizes the effects on the Company’s accumulated OCL balance attributable to interest rate swaps designated as cash flow hedge derivatives, net of tax: Three months ended March 31, 2018 2017 (In millions) Accumulated OCL beginning balance $ (60 ) $ (70 ) Reclassified from accumulated OCL to income due to realization of previously deferred amounts 4 4 Mark-to-market of cash flow hedge accounting contracts 13 2 Accumulated OCL ending balance, net of income tax benefit of $6 and $15, respectively (43 ) (64 ) Accumulated OCL attributable to noncontrolling interests (23 ) (39 ) Accumulated OCL attributable to NRG Yield, Inc. $ (20 ) $ (25 ) Losses expected to be realized from OCL during the next 12 months, net of income tax benefit of $1 $ 11

Long-term Debt (Tables)

Long-term Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of long-term debt	Long-term debt consisted of the following: March 31, 2018 December 31, 2017 March 31, 2018, interest rate % (a) Letters of Credit Outstanding at March 31, 2018 (In millions, except rates) 2019 Convertible Notes $ 345 $ 345 3.500 2020 Convertible Notes 288 288 3.250 2024 Senior Notes 500 500 5.375 2026 Senior Notes 350 350 5.000 NRG Yield LLC and NRG Yield Operating LLC Revolving Credit Facility, due 2019 (b) 75 55 L+2.500 $ 67 Project-level debt: Agua Caliente Borrower 2, due 2038 40 41 5.430 17 Alpine, due 2022 135 135 L+1.750 16 Alta Wind I - V lease financing arrangements, due 2034 and 2035 926 926 5.696 - 7.015 118 Buckthorn Solar, due 2018 and 2025 183 169 L + 1.750 10 CVSR, due 2037 731 746 2.339 - 3.775 — CVSR Holdco Notes, due 2037 188 194 4.680 13 El Segundo Energy Center, due 2023 369 400 L+1.75 - L+2.375 139 Energy Center Minneapolis, due 2025 83 83 5.950 — Energy Center Minneapolis Series D Notes, due 2031 125 125 3.550 — Laredo Ridge, due 2028 93 95 L+1.875 10 Marsh Landing, due 2023 309 318 L+2.125 38 Tapestry, due 2021 158 162 L+1.625 20 Utah Solar Portfolio, due 2022 278 278 various 13 Viento, due 2023 163 163 L+3.00 27 Walnut Creek, due 2023 259 267 L+1.625 65 Other 440 443 various 39 Subtotal project-level debt: 4,480 4,545 Total debt 6,038 6,083 Less current maturities (c) (698 ) (339 ) Less net debt issuance costs (64 ) (68 ) Less discounts (d) (15 ) (17 ) Total long-term debt $ 5,261 $ 5,659 (a) As of March 31, 2018 , L+ equals 3 month LIBOR plus x%, except for Viento, due 2023 where L+ equals 6 month LIBOR plus 3.00% and Buckthorn Solar and Utah Solar Portfolio, where L+ equals 1 month LIBOR plus x%. (b) Applicable rate is determined by the borrower leverage ratio, as defined in the credit agreement. (c) The 2019 Convertible Notes become due in February 2019 and are included in current portion of long-term debt on the Company's consolidated balance sheet as of March 31, 2018 . (d) Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The reconciliation of the Company's basic and diluted earnings per share is shown in the following tables: Three months ended March 31, 2018 2017 (In millions, except per share data) (a) Common Class A Common Class C Common Class A Common Class C Basic and diluted earnings (loss) per share attributable to NRG Yield, Inc. common stockholders Net income (loss) attributable to NRG Yield, Inc. $ 6 $ 10 $ (1 ) $ (2 ) Weighted average number of common shares outstanding — basic and diluted 35 65 35 63 Earnings (Loss) per weighted average common share — basic and diluted $ 0.16 $ 0.16 $ (0.03 ) $ (0.03 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]	The following table summarizes the Company's outstanding equity instruments that are anti-dilutive and were not included in the computation of the Company's diluted earnings per share: Three months ended March 31, 2018 2017 (In millions of shares) 2019 Convertible Notes - Common Class A 15 15 2020 Convertible Notes - Common Class C 10 10

Changes in Capital Structure St

Changes in Capital Structure Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Changes in Capital Structure [Abstract]
Schedule of Stock by Class [Table Text Block]
Dividends Declared [Table Text Block]	The following table lists the dividends paid on the Company's Class A common stock and Class C common stock during the three months ended March 31, 2018 : First Quarter 2018 Dividends per Class A share $ 0.298 Dividends per Class C share $ 0.298

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Three months ended March 31, 2018 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 79 $ 98 $ 48 $ — $ 225 Cost of operations 22 34 33 — 89 Depreciation and amortization 26 50 5 — 81 General and administrative — — — 5 5 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 31 14 10 (6 ) 49 Equity in earnings of unconsolidated affiliates 3 1 — — 4 Other income, net — 1 — — 1 Interest expense (7 ) (24 ) (2 ) (22 ) (55 ) Income (loss) before income taxes 27 (8 ) 8 (28 ) (1 ) Income tax benefit — — — (1 ) (1 ) Net Income (Loss) $ 27 $ (8 ) $ 8 $ (27 ) $ — Total Assets $ 1,815 $ 5,953 $ 424 $ 170 $ 8,362 Three months ended March 31, 2017 (In millions) Conventional Generation Renewables Thermal Corporate Total Operating revenues $ 75 $ 102 $ 44 $ — $ 221 Cost of operations 22 33 30 — 85 Depreciation and amortization 24 48 5 — 77 General and administrative — — — 4 4 Acquisition-related transaction and integration costs — — — 1 1 Operating income (loss) 29 21 9 (5 ) 54 Equity in earnings of unconsolidated affiliates 3 16 — — 19 Other income, net — 1 — — 1 Loss on debt extinguishment — (2 ) — — (2 ) Interest expense (12 ) (39 ) (3 ) (21 ) (75 ) Income (loss) before income taxes 20 (3 ) 6 (26 ) (3 ) Income tax benefit — — — (1 ) (1 ) Net Income (Loss) $ 20 $ (3 ) $ 6 $ (25 ) $ (2 )

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Reconciliation of the U.S. federal statutory rate to the Company's effective rate	The income tax provision consisted of the following: Three months ended March 31, 2018 2017 (In millions, except percentages) Loss before income taxes $ (1 ) $ (3 ) Income tax benefit (1 ) (1 ) Effective income tax rate 100.0 % 33.3 %

Nature of Business (Details)

Nature of Business (Details) $ in Millions		Mar. 31, 2018USD ($)MW	Aug. 02, 2017USD ($)	Mar. 27, 2017USD ($)MW	Mar. 31, 2018USD ($)MW	Dec. 31, 2017USD ($)
Nature of Business
Weighted Average Remaining PPA Term					15 years
Power Generation Capacity, Megawatts	[1],[2]	5,241			5,241
Power Generation Capacity, Megawatts, including portion attributable to noncontrolling interest	[1]	5,247			5,247
Megawatts Thermal Equivalent, Available Under right-to-use Provisions		134			134
Long-term Debt | $		$ 6,038			$ 6,038	$ 6,083
Conventional Generation, Utility-Scale Solar, Distributed Solar, and Wind [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]	5,118			5,118
Conventional Generation [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]	1,945			1,945
Utility-Scale Solar
Nature of Business
Power Generation Capacity, Megawatts	[1]	921			921
Distributed Solar [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]	52			52
Wind Farms [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]	2,200			2,200
Thermal [Member]
Nature of Business
Percentage of Ownership	[2]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	123			123
Steam and Chilled Water Capacity, Megawatts Thermal Equivalent	[1],[2],[3]	1,319			1,319
NRG Energy Center Dover [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
NRG Yield, Inc. [Member]
Nature of Business
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Voting Interest					44.90%
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest					53.90%
NRG Yield LLC | NRG [Member]
Nature of Business
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Voting Interest					55.10%
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest					46.10%
GenConn Middletown | Conventional Generation [Member]
Nature of Business
Equity Method Investment, Ownership Percentage		50.00%			50.00%
Power Generation Capacity, Megawatts	[1]	95			95
GenConn Devon [Member] | Conventional Generation [Member]
Nature of Business
Equity Method Investment, Ownership Percentage		50.00%			50.00%
Power Generation Capacity, Megawatts	[1]	95			95
Marsh Landing | Conventional Generation [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	720			720
El Segundo [Member] | Conventional Generation [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	550			550
Walnut Creek [Member] | Conventional Generation [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	485			485
Agua Caliente [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership		16.00%			16.00%
Power Generation Capacity, Megawatts	[1]	46			46
Alpine [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	66			66
Avenal [Member] | Utility-Scale Solar
Nature of Business
Equity Method Investment, Ownership Percentage		50.00%			50.00%
Power Generation Capacity, Megawatts	[1]	23			23
Avra Valley | Utility-Scale Solar
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	26			26
NRG Solar Blythe LLC [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	21			21
Borrego [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	26			26
CVSR [Member] | Utility-Scale Solar
Nature of Business
Equity Method Investment, Ownership Percentage		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	250			250
Desert Sunlight [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership		25.00%			25.00%
Kansas South [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	20			20
Roadrunner | Utility-Scale Solar
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	20			20
TA - High Desert LLC [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	20			20
Utah Portfolio [Member] | Utility-Scale Solar
Nature of Business
Percentage of Ownership	[4]	50.00%			50.00%
Power Generation Capacity, Megawatts	[1],[4]	265			265
AZ DG Solar Projects [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	5			5
PFMG DG Solar Projects [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	9			9
Alta I [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	150			150
Alta II [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	150			150
Alta III [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	150			150
Alta IV [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	102			102
Alta V [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	168			168
Alta X [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5]	137			137
Alta XI [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5]	90			90
South Trent | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	101			101
Spanish Fork [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	19			19
Spring Canyon II [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5]	90.10%			90.10%
Power Generation Capacity, Megawatts	[1],[5]	29			29
Laredo Ridge [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	80			80
Lookout [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	38			38
Odin Wind Farm [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	99.90%			99.90%
Power Generation Capacity, Megawatts	[1],[5],[6]	20			20
Taloga [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	130			130
Wildorado [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	161			161
Pinnacle [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	55			55
San Juan Mesa Wind Project, LLC [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	75.00%			75.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	90			90
Sleeping Bear [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	95			95
Buffalo Bear [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts	[1]	19			19
Crosswinds [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	99.00%			99.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	21			21
Elbow Creek [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	122			122
Elkhorn Ridge Wind, LLC [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	66.70%			66.70%
Power Generation Capacity, Megawatts	[1],[5],[6]	54			54
Forward [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	29			29
Goat Wind [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	100.00%			100.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	150			150
Hardin [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5],[6]	99.00%			99.00%
Power Generation Capacity, Megawatts	[1],[5],[6]	15			15
Spring Canyon [Member] | Wind Farms [Member]
Nature of Business
Power Generation Capacity, Megawatts attributed to noncontrolling interest	[1],[5]	6			6
Spring Canyon III [Member] | Wind Farms [Member]
Nature of Business
Percentage of Ownership	[5]	90.10%			90.10%
Power Generation Capacity, Megawatts	[1],[5]	25			25
Thermal [Member] | Thermal [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]	20			20
NRG Energy Center Dover [Member] | Thermal [Member]
Nature of Business
Power Generation Capacity, Megawatts	[1]	103			103
SPP Projects [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts		25			25
Other DG Assets [Member] | Distributed Solar [Member]
Nature of Business
Percentage of Ownership		100.00%			100.00%
Power Generation Capacity, Megawatts		13			13
Buckthorn Solar Drop Down Asset [Member]
Nature of Business
Power Generation Capacity, Megawatts		154			154
Business Acquisitions, Purchase Price | $		$ 42
August 2017 Drop Down Assets [Member]
Nature of Business
Business Acquisitions, Purchase Price | $			$ 44
Southern California Edison [Member] | Desert Sunlight [Member] | Utility-Scale Solar
Nature of Business
Power Generation Capacity, Megawatts	[1]	63			63
Pacific Gas and Electric [Member] | Desert Sunlight [Member] | Utility-Scale Solar
Nature of Business
Power Generation Capacity, Megawatts	[1]	75			75
Common Class D [Member] | NRG Yield LLC
Nature of Business
Sale of Stock, Percentage of Ownership after Transaction					100.00%
Unconsolidated Solar Partnerships [Member]
Nature of Business
Power Generation Capacity, Megawatts		262			262
Agua Caliente [Member]
Nature of Business
Long-term Debt | $		$ 815			$ 815
March 2017 Drop Down Assets [Member]
Nature of Business
Business Acquisitions, Purchase Price | $				$ 128
Agua Caliente Borrower 2 [Member]
Nature of Business
Equity Method Investment, Ownership Percentage		16.00%			16.00%
Power Generation Capacity, Megawatts				46
Agua Caliente Borrower 2 [Member] | NRG [Member]
Nature of Business
Percentage of Ownership				51.00%
Buckthorn Solar Drop Down Asset [Member]
Nature of Business
Long-term Debt | $		$ 183			$ 183	$ 169
Buckthorn Solar Drop Down Asset [Member] | Buckthorn Solar Drop Down Asset [Member]
Nature of Business
Long-term Debt | $		$ 183			$ 183
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs.
[3]	For thermal energy, net capacity represents MWt for steam or chilled water and excludes 134 MWt available under the right-to-use provisions contained in agreements between two of the Company's thermal facilities and certain of its customers.
[4]	Represents interests in Four Brothers Solar, LLC, Granite Mountain Holdings, LLC, and Iron Springs Holdings, LLC, all acquired as part of the March 2017 Drop Down Assets (ownership percentage is based upon cash to be distributed).
[5]	Projects are part of tax equity arrangements
[6]	Projects are part of NRG Wind TE Holdco portfolio.

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Details) - USD ($)		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017
Summary of Significant Accounting Policies [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		$ 1,358,000,000			$ 1,285,000,000
Finite-Lived Intangible Assets, Accumulated Amortization		255,000,000			237,000,000
Stockholders' Equity Attributable to Noncontrolling Interest		(371,000,000)			(412,000,000)	[1]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		2,126,000,000			2,159,000,000	[1]
Pre-acquisition net income of the Buckthorn Solar Drop Down Asset		4,000,000	$ 13,000,000	[1]
Comprehensive loss		(11,000,000)	(9,000,000)	[1]
Distributions to NRG, net		$ (22,000,000)
Dividends Payable, Date Declared		Apr. 24, 2018
Common Stock, Dividends, Per Share, Declared		$ 0.309
Dividends Payable, Date to be Paid		Jun. 15, 2018
Dividends Payable, Date of Record		Jun. 1, 2018
Revenue from Contract with Customer, Excluding Assessed Tax		$ 61,000,000
Capitalized Contract Cost, Amortization		(17,000,000)
Total operating revenues		225,000,000	221,000,000	[1]
Operating Leases, Income Statement, Contingent Revenue		181,000,000
Accounts Receivable, Net		82,000,000
Buckthorn Solar Drop Down Asset [Member]
Summary of Significant Accounting Policies [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					21,000,000
Payment for the Buckthorn Solar Drop Down Asset		(42,000,000)
Financial Institutions [Member]
Summary of Significant Accounting Policies [Line Items]
Capital contributions from tax equity investors, net of distributions		$ 30,000,000
Common Class B [Member]
Summary of Significant Accounting Policies [Line Items]
Distribution Made to Limited Liability Company (LLC) Member, Distributions Paid, Per Unit		$ 0.298
Common Class D [Member]
Summary of Significant Accounting Policies [Line Items]
Distribution Made to Limited Liability Company (LLC) Member, Distributions Paid, Per Unit		$ 0.298
Scenario, Previously Reported [Member]
Summary of Significant Accounting Policies [Line Items]
Stockholders' Equity Attributable to Noncontrolling Interest					(391,000,000)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					$ 2,138,000,000
Pre-acquisition net income of the Buckthorn Solar Drop Down Asset	[2]		12,000,000
Total operating revenues	[2]		218,000,000
Customer Contracts [Member]
Summary of Significant Accounting Policies [Line Items]
Accounts Receivable, Net		$ 26,000,000
Lease Agreements [Member]
Summary of Significant Accounting Policies [Line Items]
Accounts Receivable, Net		56,000,000
Conventional Generation [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0
Capitalized Contract Cost, Amortization		(1,000,000)
Total operating revenues		79,000,000	75,000,000
Operating Leases, Income Statement, Contingent Revenue		(80,000,000)
Renewables [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		12,000,000
Capitalized Contract Cost, Amortization		(15,000,000)
Total operating revenues		98,000,000	102,000,000
Operating Leases, Income Statement, Contingent Revenue		(101,000,000)
Thermal [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		49,000,000
Capitalized Contract Cost, Amortization		(1,000,000)
Total operating revenues		48,000,000	$ 44,000,000
Operating Leases, Income Statement, Contingent Revenue		0
Energy Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	114,000,000
Operating Leases, Income Statement, Contingent Revenue		102,000,000
Energy Revenue [Member] | Conventional Generation [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	1,000,000
Operating Leases, Income Statement, Contingent Revenue		1,000,000
Energy Revenue [Member] | Renewables [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	112,000,000
Operating Leases, Income Statement, Contingent Revenue		101,000,000
Energy Revenue [Member] | Thermal [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	1,000,000
Operating Leases, Income Statement, Contingent Revenue		0
Capacity Revenue [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	82,000,000
Operating Leases, Income Statement, Contingent Revenue		79,000,000
Capacity Revenue [Member] | Conventional Generation [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	79,000,000
Operating Leases, Income Statement, Contingent Revenue		79,000,000
Capacity Revenue [Member] | Renewables [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	0
Operating Leases, Income Statement, Contingent Revenue		0
Capacity Revenue [Member] | Thermal [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	3,000,000
Operating Leases, Income Statement, Contingent Revenue		0
Products And Services, Other [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		46,000,000
Products And Services, Other [Member] | Conventional Generation [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0
Products And Services, Other [Member] | Renewables [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,000,000
Products And Services, Other [Member] | Thermal [Member]
Summary of Significant Accounting Policies [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 45,000,000
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	As previously reported in the Company's Form 10-Q for the quarter ended March 31, 2017
[3]	The following amounts of energy and capacity revenue relate to leases and are accounted for under ASC 840:

Business Acquisitions Busines36

Business Acquisitions Business Acquisitions - Central CA Fuel Cell (Details) $ in Millions		Apr. 18, 2018USD ($)MW	Mar. 31, 2018MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts	[1],[2]		5,241
Subsequent Event [Member] | Central CA Fuel Cell 1 [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred | $		$ 11
Power Generation Capacity, Megawatts		2.8
Power Purchase Agreement Period		20 years
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs.

Business Acquisitions Busines37

Business Acquisitions Business Acquisitions - Buckthorn Solar Drop Down Asset (Details) $ in Millions		Mar. 31, 2018USD ($)MW	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Assets, Current		$ 425	$ 482	[1]
Power Generation Capacity, Megawatts | MW	[2],[3]	5,241
Long-term Debt		$ 6,038	6,083
Property, Plant and Equipment, Net		5,340	5,410	[1]
Other Assets		2,597	2,597	[1]
Total Assets		8,362	8,489	[1]
Debt, Long-term and Short-term, Combined Amount			5,998
Other Liabilities			332
Liabilities		6,236	6,330	[1]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ 2,126	2,159	[1]
Buckthorn Solar Drop Down Asset [Member]
Business Acquisition [Line Items]
Assets, Current			0
Power Generation Capacity, Megawatts | MW		154
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets		$ 20
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		212
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets		3
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		235
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	[4]	176
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other		15
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		191
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		19
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		25
Business Combination, Consideration Transferred		42
Property, Plant and Equipment, Net			206
Other Assets			0
Total Assets			206
Debt, Long-term and Short-term, Combined Amount			161
Other Liabilities			24
Liabilities			185
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			21
Buckthorn Solar Drop Down Asset [Member]
Business Acquisition [Line Items]
Long-term Debt		183	169
Buckthorn Solar Drop Down Asset [Member] | Buckthorn Solar Drop Down Asset [Member]
Business Acquisition [Line Items]
Long-term Debt		$ 183
Scenario, Previously Reported [Member]
Business Acquisition [Line Items]
Assets, Current			482
Property, Plant and Equipment, Net			5,204
Other Assets			2,597
Total Assets			8,283
Debt, Long-term and Short-term, Combined Amount			5,837
Other Liabilities			308
Liabilities			6,145
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			$ 2,138
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018.
[3]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs.
[4]	Net of $7 million of net debt issuance costs.

Business Acquisitions Busines38

Business Acquisitions Business Acquisitions - November 2017 Drop Down (Details) $ in Millions		Nov. 02, 2017USD ($)	Mar. 31, 2018USD ($)MW	Dec. 31, 2017USD ($)	Nov. 01, 2017USD ($)MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW	[1],[2]		5,241
Long-term Debt			$ 6,038	$ 6,083
November 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW					38
Business Combination, Consideration Transferred		$ 74
November 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Long-term Debt					$ 26
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs.

Business Acquisitions Busines39

Business Acquisitions Business Acquisitions - August 2017 Drop Down (Details) - USD ($) $ in Millions		Nov. 02, 2017	Aug. 02, 2017	Mar. 27, 2017	Mar. 31, 2018	Mar. 31, 2017		Aug. 01, 2017
Business Acquisition [Line Items]
Total operating revenues					$ 225	$ 221	[1]
Operating Income (Loss)					49	54	[1]
Net Income (Loss)					0	(2)	[1]
Less: Pre-acquisition net income of Drop Down Assets					4	13	[1]
Less: Loss attributable to noncontrolling interests					(20)	(12)	[1]
Net Income (Loss) Available to Common Stockholders, Basic					16	(3)	[1]
August 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred			$ 44
Business Combination, Contingent Consideration, Liability					$ 8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net								$ 87
Total operating revenues						0
Operating Income (Loss)						0
Net Income (Loss)						0
Less: Pre-acquisition net income of Drop Down Assets						2
Less: Loss attributable to noncontrolling interests						(2)
Net Income (Loss) Available to Common Stockholders, Basic						0
November 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 74
Total operating revenues						3
Operating Income (Loss)						0
Net Income (Loss)						(1)
Less: Pre-acquisition net income of Drop Down Assets						(1)
Less: Loss attributable to noncontrolling interests						0
Net Income (Loss) Available to Common Stockholders, Basic						0
August 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired								25.00%
March 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred				$ 128
Scenario, Previously Reported [Member]
Business Acquisition [Line Items]
Total operating revenues	[2]					218
Operating Income (Loss)	[2]					54
Net Income (Loss)	[2]					(1)
Less: Pre-acquisition net income of Drop Down Assets	[2]					12
Less: Loss attributable to noncontrolling interests	[2]					(10)
Net Income (Loss) Available to Common Stockholders, Basic	[2]					$ (3)
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	As previously reported in the Company's Form 10-Q for the quarter ended March 31, 2017

Business Acquisitions Busines40

Business Acquisitions Business Acquisitions - March 2017 Drop Down (Details) $ in Millions		Mar. 27, 2017USD ($)MW	Mar. 31, 2018USD ($)MW
Business Acquisition [Line Items]
Power Generation Capacity, Megawatts | MW	[1],[2]		5,241
Agua Caliente Borrower 2 [Member]
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage			16.00%
Percentage of NRG's Ownership		31.00%
Power Generation Capacity, Megawatts | MW		46
Power Purchase Agreement Period		25 years
Remaining Power Purchase Agreement term		22 years
Non-Recourse Debt		$ 41
Utah Portfolio [Member]
Business Acquisition [Line Items]
Remaining Power Purchase Agreement term		20 years
Percentage of Cash Available for Distributions			50.00%
Non-Recourse Debt		$ 287
March 2017 Drop Down Assets [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		128
Business Acquisition, Consideration Transferred, Working Capital			$ 4
Business Combination, Separately Recognized Transactions, Net Gains and Losses		$ 8
NRG [Member] | Agua Caliente Borrower 2 [Member]
Business Acquisition [Line Items]
Percentage of Ownership		51.00%
NRG [Member] | Utah Portfolio [Member]
Business Acquisition [Line Items]
Percentage of Cash Available for Distributions			50.00%
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs.

Variable Interest Entities Vari

Variable Interest Entities Variable Interest Entities - Consolidated Entities (Details) $ in Millions		Mar. 31, 2018USD ($)MW	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Power Generation Capacity, Megawatts | MW	[1],[2]	5,241
Other Assets		$ 2,597	$ 2,597	[3]
Property, Plant and Equipment, Net		5,340	5,410	[3]
Total Assets		8,362	8,489	[3]
Liabilities		6,236	6,330	[3]
November 2015 Drop Down Assets [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets		172
Property, Plant and Equipment, Net		369
Intangible Assets		2
Total Assets		543
Liabilities		195
Noncontrolling Interest in Variable Interest Entity		9
Net Assets		339
Alta X and XI TE Holdco [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets		18
Property, Plant and Equipment, Net		430
Intangible Assets		259
Total Assets		707
Liabilities		8
Noncontrolling Interest in Variable Interest Entity		77
Net Assets		622
Spring Canyon [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets		2
Property, Plant and Equipment, Net		94
Intangible Assets		0
Total Assets		96
Liabilities		5
Noncontrolling Interest in Variable Interest Entity		50
Net Assets		41
Buckthorn Solar Drop Down Asset [Member]
Schedule of Equity Method Investments [Line Items]
Other Assets		23
Property, Plant and Equipment, Net		212
Intangible Assets		0
Total Assets		235
Liabilities		191
Noncontrolling Interest in Variable Interest Entity		19
Net Assets		$ 25
Buckthorn Solar Drop Down Asset [Member]
Schedule of Equity Method Investments [Line Items]
Power Generation Capacity, Megawatts | MW		154
Business Combination, Consideration Transferred		$ 42
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		$ 19
Other Assets			0
Property, Plant and Equipment, Net			206
Total Assets			206
Liabilities			$ 185
[1]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018.
[2]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs.
[3]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Variable Interest Entities Va42

Variable Interest Entities Variable Interest Entities - Unconsolidated Entities (Details) $ in Millions		3 Months Ended
		Mar. 31, 2018USD ($)MW	Mar. 31, 2017USD ($)		Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		$ 1,169			$ 1,178	[1]
Power Generation Capacity, Megawatts | MW	[2],[3]	5,241
Operating revenues		$ 225	$ 221	[1]
Operating Income (Loss)		49	54	[1]
Net Income (Loss)		0	(2)	[1]
Assets, Current		425			482	[1]
Liabilities, Current		859			540	[1]
Liabilities, Noncurrent		5,377			5,790	[1]
Four Brothers Solar [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		209
Granite Mountain Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		76
Iron Springs Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		53
Gen Conn Energy LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		100
NRG DGPV Holdco 1 [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		73
NRG RPV Holdco [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		52
NRG DGPV Holdco 2 [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		61
NRG DGPV Holdco 3 [Member]
Schedule of Equity Method Investments [Line Items]
Equity investments in affiliates		62
Payments to Acquire Interest in Subsidiaries and Affiliates		6
Due to Affiliate		$ 16
Power Generation Capacity, Megawatts | MW		59
Remaining Lease Term		22 years
Utah Portfolio [Member]
Schedule of Equity Method Investments [Line Items]
Operating revenues		$ 11	5
Operating Income (Loss)		0	(1)
Net Income (Loss)		3	$ (2)
Assets, Current		92			74
Assets, Noncurrent		718			671
Liabilities, Current		84			83
Liabilities, Noncurrent		236			216
NRG DGPV Holdco [Member]
Schedule of Equity Method Investments [Line Items]
Redeemable Noncontrolling Interest, Equity, Carrying Amount		$ 42			$ 44
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	Net capacity represents the maximum, or rated, generating capacity of the facility multiplied by the Company's percentage ownership in the facility as of March 31, 2018.
[3]	The Company's total generation capacity is net of 6 MWs for noncontrolling interest for Spring Canyon II and III. The Company's generation capacity including this noncontrolling interest was 5,247 MWs.

Variable Interest Entities Va43

Variable Interest Entities Variable Interest Entities - Utah Solar Portfolio (Details) - Utah Portfolio [Member]	Mar. 31, 2018
Variable Interest Entity [Line Items]
Percentage of Cash Available for Distributions	50.00%
Capital Unit, Class A [Member]
Variable Interest Entity [Line Items]
Percentage of Ownership	100.00%
Financial Institutions [Member] | Capital Unit, Class B [Member]
Variable Interest Entity [Line Items]
Taxable Income Allocation, Pre-Flip	99.00%
Taxable Income Allocation, Post-Flip	50.00%

Variable Interest Entities Va44

Variable Interest Entities Variable Interest Entities - Debt Held by Unconsolidated Affiliates (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Long-term Debt	$ 6,038	$ 6,083
Agua Caliente [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt	$ 815
Debt Instrument, Basis Spread on Libor Rate	0.375%
Agua Caliente Borrower 2 [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	16.00%
Pro-Rate Share of Debt Held by Unconsolidated Affiliates	$ 130

Fair Value of Financial Instr45

Fair Value of Financial Instruments Fair Value of Financial Instruments - Balance Sheet Grouping (Details) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financing Receivable, Net	[1]	$ 9	$ 13
Long-term Debt and Capital Lease Obligations, Including Current Maturities	[2]	6,020	6,099
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financing Receivable, Net	[1]	9	13
Long-term Debt and Capital Lease Obligations, Including Current Maturities	[2]	6,023	6,066
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt and Capital Lease Obligations, Including Current Maturities		1,472	1,502
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt and Capital Lease Obligations, Including Current Maturities		$ 4,548	$ 4,597
[1]	(a) Carrying amount as of December 31, 2017, includes the long-term portion of notes receivable, which is recorded in other noncurrent assets on the Company's consolidated balance sheets.
[2]	(b) Excludes deferred financing costs, which are recorded as a reduction to long-term debt on the Company's consolidated balance sheets.

Fair Value of Financial Instr46

Fair Value of Financial Instruments Fair Value of Financial Instruments - Recurring Fair Value (Details) - USD ($)		Mar. 31, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	$ 17,000,000		$ 2,000,000
Derivative Liability, Fair Value, Gross Liability		26,000,000		49,000,000
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[2]	17,000,000		2,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net		0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value, Gross Liability	[2]	26,000,000		49,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net		0		0
Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	[3]	1,000,000
Derivative Liability, Fair Value, Gross Liability		2,000,000	[3]	1,000,000
Commodity Contract [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[2]	0		1,000,000
Derivative Liability, Fair Value, Gross Liability	[2]	2,000,000		1,000,000
Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset		17,000,000		1,000,000
Derivative Liability, Fair Value, Gross Liability		24,000,000		48,000,000
Interest Rate Contract [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Fair Value, Gross Asset	[2]	17,000,000		1,000,000
Derivative Liability, Fair Value, Gross Liability	[2]	$ 24,000,000		$ 48,000,000
[1]	Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of March 31, 2018 and December 31, 2017.
[2]	(a) There were no derivative assets or liabilities classified as Level 1 or Level 3 as of March 31, 2018 and December 31, 2017.
[3]	There were no commodity contracts classified as derivative assets as of March 31, 2018.

Fair Value of Financial Instr47

Fair Value of Financial Instruments Fair Value of Financial Instruments - Credit Risk and Derivative FV Measurements (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair Value Assets, Valuation Techniques, Impact of Credit Reserve to Fair Value	$ 0
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 2,600
Estimated Counterparty Credit Risk Exposure to Certain Counterparties, Period	5 years

Accounting for Derivative Ins48

Accounting for Derivative Instruments and Hedging Activities Accounting for Derivative Instruments and Hedging Activities - FV of Derivatives (Details) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	$ 17		$ 2
Derivative Liability, Fair Value, Gross Liability		26		49
Fair Value of Gross Derivative Assets/(Liabilities), Net		(9)		(47)
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset		0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral		(9)		(47)
Derivative, Collateral, Right to Reclaim Cash		0		0
Derivative, Collateral, Obligation to Return Cash		0		0
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	8		1
Derivative Liability, Fair Value, Gross Liability		8		13
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	9		1
Derivative Liability, Fair Value, Gross Liability		18		36
Interest Rate Contract Current [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	1		0
Derivative Liability, Fair Value, Gross Liability		2		4
Interest Rate Contract Current [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	0		0
Derivative Liability, Fair Value, Gross Liability		6		13
Interest Rate Contract Non Current [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	7		1
Derivative Liability, Fair Value, Gross Liability		6		9
Interest Rate Contract Non Current [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	9		0
Derivative Liability, Fair Value, Gross Liability		10		22
Commodity Contract Current [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]			1
Derivative Liability, Fair Value, Gross Liability		1		1
Commodity Contract Non Current [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]			0
Derivative Liability, Fair Value, Gross Liability		1		0
Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		0	[2]	1
Derivative Liability, Fair Value, Gross Liability		2	[2]	1
Derivative Asset, Fair Value, Gross Liability		0	[2]	0
Derivative Liability, Fair Value, Gross Asset		0	[2]	0
Derivative Asset		0	[2]	1
Derivative Liability		2	[2]	1
Fair Value of Gross Derivative Assets/(Liabilities), Net		(2)	[2]	0
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset		0	[2]	0
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral		(2)	[2]	0
Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		17		1
Derivative Liability, Fair Value, Gross Liability		24		48
Derivative Asset, Fair Value, Gross Liability		2		1
Derivative Liability, Fair Value, Gross Asset		2		1
Derivative Asset		15		0
Derivative Liability		22		47
Fair Value of Gross Derivative Assets/(Liabilities), Net		(7)		(47)
Derivative Asset Fair Value Gross Liability Net Of Derivative Liability Fair Value Gross Asset		0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral Net Of Derivative Liability, Fair Value, Amount Offset Against Collateral		(7)		(47)
Interest [Member] | United States of America, Dollars
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		2,001		2,050
Natural Gas [Member] | MMbtu [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		$ 1		$ 2
[1]	Derivative Assets balances classified as current are included within the prepayments and other current assets line item of the consolidated balance sheets as of March 31, 2018 and December 31, 2017.
[2]	There were no commodity contracts classified as derivative assets as of March 31, 2018.

Accounting for Derivative Ins49

Accounting for Derivative Instruments and Hedging Activities Accounting for Derivative Instruments and Hedging Activities - AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016
Derivative [Line Items]
Accumulated Other Comprehensive Loss, Net of Tax	$ (43)		$ (60)		$ (70)	$ (64)
Accumulated Other Comprehensive Loss, Cumulative Change in Loss from Cash Flow Hedges, Tax Amount	(6)					(15)
Reclassified from accumulated OCL to income due to realization of previously deferred amounts	4	$ 4
Mark-to-market of cash flow hedge accounting contracts	13	2
Accumulated other comprehensive loss	(20)		$ (28)	[1]		$ (25)
Losses expected to be realized from OCL during the next 12 months, net of income tax benefit of $1	11
Losses expected to be realized from OCL during the next 12 months, Tax Amount	(1)
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net		$ 0
Noncontrolling Interest [Member]
Derivative [Line Items]
Accumulated other comprehensive loss	$ (23)						$ (39)
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Accounting for Derivative Ins50

Accounting for Derivative Instruments and Hedging Activities Accounting for Derivative Instruments and Hedging Activities - Impact to Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (24)	$ (4)

Long-term Debt Long-term Debt -

Long-term Debt Long-term Debt - Debt Table (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt		$ 6,038	$ 6,083
Current portion of long-term debt		(698)	(339)	[1]
Debt Issuance Costs, Net		(64)	(68)
Long-term Debt, Excluding Current Maturities		5,261	5,659
Debt Instrument, Unamortized Discount	[2]	(15)	(17)
3.5% Convertible Notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 345	345
Debt Instrument, Interest Rate, Stated Percentage	[3]	3.50%
3.25% Convertible Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 288	288
Debt Instrument, Interest Rate, Stated Percentage	[3]	3.25%
5.375% Senior Notes due in 2024 [Member]
Debt Instrument [Line Items]
Senior Notes		$ 500	500
Debt Instrument, Interest Rate, Stated Percentage	[3]	5.375%
5.00% Senior Notes due in 2026 [Member]
Debt Instrument [Line Items]
Senior Notes		$ 350	350
Debt Instrument, Interest Rate, Stated Percentage	[3]	5.00%
NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 75	55
Debt Instrument, Description of Variable Rate Basis	[3]	3 month LIBOR
Debt Instrument, Basis Spread on Variable Rate	[2]	2.50%
Alta Wind Asset Management, due 2031 [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	[3]	3 month LIBOR
Debt Instrument, Basis Spread on Variable Rate		2.375%
Agua Caliente Borrower 2 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 40	41
Debt Instrument, Interest Rate, Stated Percentage	[3]	5.43%
Alpine Financing Agreement, due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 135	135
Debt Instrument, Description of Variable Rate Basis	[3]	3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate		1.75%
Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 926	926
Buckthorn Solar Drop Down Asset [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 183	169
Debt Instrument, Description of Variable Rate Basis		1-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate		1.75%
CVSR, due 2037
Debt Instrument [Line Items]
Long-term Debt		$ 731	746
CVSR Holdco due 2037 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 188	194
Debt Instrument, Interest Rate, Stated Percentage	[3]	4.68%
El Segundo Energy Center, due 2023
Debt Instrument [Line Items]
Long-term Debt		$ 369	400
Debt Instrument, Description of Variable Rate Basis	[3]	3-Month LIBOR
El Segundo Energy Center due 2023 Tranche B [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		2.375%
El Segundo Energy Center due 2023 Tranche A [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.75%
Energy Center Minneapolis, due 2025
Debt Instrument [Line Items]
Long-term Debt		$ 83	83
Debt Instrument, Interest Rate, Stated Percentage		5.95%
Energy Center Minneapolis Series D Notes, due 2031
Debt Instrument [Line Items]
Long-term Debt		$ 125	125
Debt Instrument, Interest Rate, Stated Percentage	[3]	3.55%
Laredo Ridge Wind, LLC, due in 2026 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 93	95
Debt Instrument, Description of Variable Rate Basis	[3]	3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate		1.875%
Marsh Landing Term Loan Facility [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 309	318
Marsh Landing Tranche B due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	[3]	3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate		2.125%
Tapestry Wind LLC due in 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 158	162
Debt Instrument, Description of Variable Rate Basis	[3]	3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate		1.625%
Utah Solar Portfolio, due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 278	278
Viento Funding II, Inc., due in 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 163	163
Debt Instrument, Description of Variable Rate Basis	[3]	3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate		3.00%
Walnut Creek Energy, LLC, due in 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 259	267
Debt Instrument, Description of Variable Rate Basis	[3]	3-Month LIBOR
Debt Instrument, Basis Spread on Variable Rate		1.625%
Other Debt [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 440	443
Letters of Credit Outstanding, Amount		39
Project [Domain]
Debt Instrument [Line Items]
Long-term Debt		$ 4,480	$ 4,545
Minimum [Member] | Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.696%
Minimum [Member] | CVSR, due 2037
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.339%
Maximum [Member] | Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.015%
Maximum [Member] | CVSR, due 2037
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.775%
Letter of Credit [Member] | NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		$ 67
Letter of Credit [Member] | Agua Caliente Borrower 2 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		17
Letter of Credit [Member] | Alpine Financing Agreement, due 2022 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		16
Letter of Credit [Member] | Alta Wind I-V, lease financing arrangement, due 2034 and 2035 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		118
Letter of Credit [Member] | Buckthorn Solar Drop Down Asset [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		10
Letter of Credit [Member] | CVSR, due 2037
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		0
Letter of Credit [Member] | CVSR Holdco due 2037 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		13
Letter of Credit [Member] | El Segundo Energy Center, due 2023
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		139
Letter of Credit [Member] | Energy Center Minneapolis, due 2025
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		0
Letter of Credit [Member] | Energy Center Minneapolis Series D Notes, due 2031
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		0
Letter of Credit [Member] | Laredo Ridge Wind, LLC, due in 2026 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		10
Letter of Credit [Member] | Marsh Landing Term Loan Facility [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		38
Letter of Credit [Member] | Tapestry Wind LLC due in 2021 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		20
Letter of Credit [Member] | Utah Solar Portfolio, due 2022 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		13
Letter of Credit [Member] | Viento Funding II, Inc., due in 2023 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		27
Letter of Credit [Member] | Walnut Creek Energy, LLC, due in 2023 [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount		$ 65
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes.
[3]	As of March 31, 2018, L+ equals 3 month LIBOR plus x%, except for Viento, due 2023 where L+ equals 6 month LIBOR plus 3.00%

Long-term Debt Long-term Debt52

Long-term Debt Long-term Debt - Debt Disclosures (Details) - USD ($) $ in Millions		Apr. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,500
Long-term Debt			6,038	$ 6,083
NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding			75
Proceeds from Issuance of Debt			20
Long-term Debt			$ 75	55
Debt Instrument, Basis Spread on Variable Rate	[1]		2.50%
Buckthorn Solar Drop Down Asset [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 183	$ 169
Debt Instrument, Basis Spread on Variable Rate			1.75%
Letter of Credit [Member] | NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			$ 67
Letter of Credit [Member] | Buckthorn Solar Drop Down Asset [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount			10
Buckthorn Solar Drop Down Asset [Member] | Buckthorn Solar Drop Down Asset [Member]
Debt Instrument [Line Items]
Long-term Debt			$ 183
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage			80.00%
Subsequent Event [Member] | NRG Yield Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	[1]	1.75%
[1]	Discounts relate to the 2019 Convertible Notes and 2020 Convertible Notes.

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic		$ 16	$ (3)	[1]
Common Class A [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic	[2]	$ 6	$ (1)
Weighted Average Number of Shares Outstanding, Basic and Diluted	[2]	35	35
Earnings (Loss) per Weighted Average Class A and Class C Common Share - Basic and Diluted	[2]	$ 0.16	$ (0.03)
Common Class C [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic	[2]	$ 10	$ (2)
Weighted Average Number of Shares Outstanding, Basic and Diluted	[2]	65	63
Earnings (Loss) per Weighted Average Class A and Class C Common Share - Basic and Diluted	[2]	$ 0.16	$ (0.03)
3.5% Convertible Notes due 2019 [Member] | Common Class A [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		15	15
3.25% Convertible Notes due 2020 [Member] | Common Class C [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		10	10
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.
[2]	(a) Basic and diluted earnings (loss) per share might not recalculate due to presenting values in millions rather than whole dollars.

Changes in Capital Structure Ch

Changes in Capital Structure Changes in Capital Structure - Stock Issuance (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 03, 2018	Mar. 31, 2018
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share		$ 0.01
ATM Program, Maximum Dollar Value of Shares to Be Issued		$ 150,000
Common Stock, Shares, Issued		936,662
Proceeds from Issuance of Common Stock, Before Commission Fees		$ 16,000
Commission Fees		$ 105
NRG Yield, Inc. [Member]
Class of Stock [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		53.90%
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Voting Interest		44.90%
Subsequent Event [Member]
Class of Stock [Line Items]
Proceeds from Issuance of Common Stock, Before Commission Fees	$ 6,000
ATM program, dollar value of shares remaining	$ 99,000

Changes in Capital Structure 55

Changes in Capital Structure Changes in Capital Structure - Dividends (Details) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Class of Stock [Line Items]
Dividends Per Common Share, Cash Paid	$ 0.298
Dividends Payable, Date Declared	Apr. 24, 2018
Common Stock, Dividends, Per Share, Declared	$ 0.309
Dividends Payable, Date to be Paid	Jun. 15, 2018
Dividends Payable, Date of Record	Jun. 1, 2018
Preferred Stock, Shares Authorized	10,000,000		10,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Common Class A [Member]
Class of Stock [Line Items]
Dividends Per Common Share, Cash Paid	0.298	$ 0.260
Common Class C [Member]
Class of Stock [Line Items]
Dividends Per Common Share, Cash Paid	$ 0.298	$ 0.260

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017	[1]
Segment Reporting
Operating revenues	$ 225	$ 221	[1]
Cost of operations	89	85
Depreciation and amortization	81	77	[1]
General and administrative	5	4	[1]
Acquisition-related transaction and integration costs	1	1	[1]
Operating Income (Loss)	49	54	[1]
Equity in earnings of unconsolidated affiliates	4	19	[1]
Other income, net	1	1	[1]
Loss on debt extinguishment	0	(2)	[1]
Interest expense	(55)	(75)	[1]
Income (loss) before income taxes	(1)	(3)	[1]
Income tax benefit	(1)	(1)	[1]
Net Income (Loss)	0	(2)	[1]
Total Assets	8,362			$ 8,489
Conventional Generation
Segment Reporting
Operating revenues	79	75
Cost of operations	22	22
Depreciation and amortization	26	24
General and administrative	0	0
Acquisition-related transaction and integration costs	0	0
Operating Income (Loss)	31	29
Equity in earnings of unconsolidated affiliates	3	3
Other income, net	0	0
Loss on debt extinguishment		0
Interest expense	(7)	(12)
Income (loss) before income taxes	27	20
Income tax benefit	0	0
Net Income (Loss)	27	20
Total Assets	1,815
Renewables [Member]
Segment Reporting
Operating revenues	98	102
Cost of operations	34	33
Depreciation and amortization	50	48
General and administrative	0	0
Acquisition-related transaction and integration costs	0	0
Operating Income (Loss)	14	21
Equity in earnings of unconsolidated affiliates	1	16
Other income, net	1	1
Loss on debt extinguishment		(2)
Interest expense	(24)	(39)
Income (loss) before income taxes	(8)	(3)
Income tax benefit	0	0
Net Income (Loss)	(8)	(3)
Total Assets	5,953
Thermal [Member]
Segment Reporting
Operating revenues	48	44
Cost of operations	33	30
Depreciation and amortization	5	5
General and administrative	0	0
Acquisition-related transaction and integration costs	0	0
Operating Income (Loss)	10	9
Equity in earnings of unconsolidated affiliates	0	0
Other income, net	0	0
Loss on debt extinguishment		0
Interest expense	(2)	(3)
Income (loss) before income taxes	8	6
Income tax benefit	0	0
Net Income (Loss)	8	6
Total Assets	424
Corporate
Segment Reporting
Operating revenues	0	0
Cost of operations	0	0
Depreciation and amortization	0	0
General and administrative	5	4
Acquisition-related transaction and integration costs	1	1
Operating Income (Loss)	(6)	(5)
Equity in earnings of unconsolidated affiliates	0	0
Other income, net	0	0
Loss on debt extinguishment		0
Interest expense	(22)	(21)
Income (loss) before income taxes	(28)	(26)
Income tax benefit	(1)	(1)
Net Income (Loss)	(27)	$ (25)
Total Assets	$ 170
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Income Taxes (Provision) (Detai

Income Taxes (Provision) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Loss before income taxes	$ (1)	$ (3)	[1]
Income tax benefit	$ (1)	$ (1)	[1]
Effective income tax rate	100.00%	33.30%
U.S. federal statutory rate (as a percent)	21.00%	35.00%
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction
General and administrative	$ 5	$ 4	[1]
NRG [Member]
Related Party Transaction
Revenue from Related Parties	3	4
NRG RENOM [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party	7	6
Due to Affiliate	4				$ 5
Thermal [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party	4	4
Marsh Landing [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party	3	3
Due to Affiliate	3			$ 1
NRG Yield [Member] | NRG [Member]
Related Party Transaction
General and administrative	2	2
NRG Yield [Member] | NRG [Member] | Scenario, Plan [Member]
Related Party Transaction
Management Services Fee, Annual	9
NECP [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Amount to be Paid Upon Completion of Project	88
Operations and Maintenance services [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party	10	10
Due to Affiliate	9			$ 13
Operations and Maintenance services [Member] | GCE Holding LLC [Member] | NRG [Member]
Related Party Transaction
Related Party Transaction, Expenses from Transactions with Related Party	$ 1	$ 1
[1]	(a) Retrospectively adjusted as discussed in Note 1, Nature of Business.