Additional Debt Borrowed

No definition available.

Name:	nrg_AdditionalDebtBorrowed
Namespace Prefix:	nrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Business Acquisitions, Consideration Transferred, Purchase Price

+ References

No definition available.

+ Details

Name:	nrg_BusinessAcquisitionsConsiderationTransferredPurchasePrice
Namespace Prefix:	nrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of Ownership

+ References

No definition available.

+ Details

Name:	nrg_PercentageOfOwnership
Namespace Prefix:	nrg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The generation capacity of the entity's power generation facilities as of the balance sheet date, expressed in megawatts.

+ References

No definition available.

+ Details

Name:	nrg_PowerGenerationCapacityMegawatts
Namespace Prefix:	nrg_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Remaining Lease Term

+ References

No definition available.

+ Details

Name:	nrg_RemainingLeaseTerm
Namespace Prefix:	nrg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6911338&loc=d3e6819-128478

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of other assets expected to be realized or consumed before one year or the normal operating cycle, if longer, acquired at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of identifiable intangible assets recognized as of the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 55
-Paragraph 37
-URI http://asc.fasb.org/extlink&oid=84160947&loc=d3e2207-128464

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

+ References

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of property, plant, and equipment recognized as of the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 55
-Paragraph 37
-URI http://asc.fasb.org/extlink&oid=84160947&loc=d3e2207-128464

+ Details

Name:	us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cash outflow, made soon after acquisition date of business combination, to settle contingent consideration liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentForContingentConsiderationLiabilityInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=nrg_SunEdisonUtilityScaleSolarandWindMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=nrg_SunEdisonSolarDistributedGenerationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=nrg_DesertSunlightMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=nrg_MechanicallycompleteSolarAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=nrg_IndevelopmentWindAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=nrg_ConstructionreadyandindevelopmentsolarassetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=nrg_IndevelopmentsolarassetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=nrg_ConstructionreadySolarFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nrg_EconomicEntityAxis=nrg_NrgMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nrg_ConsiderationbyTypeAxis=nrg_PostclosingobligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=nrg_NonRecourseDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nrg_UtahPortfolioMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Discontinued Operations, Acquisitions and Dispositions - Acquisitions (Details) $ in Millions					3 Months Ended	12 Months Ended
	Nov. 09, 2016 USD ($)	Nov. 02, 2016 USD ($) MW	Oct. 03, 2016 USD ($) MW	Jun. 29, 2015 USD ($) MW	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) MW
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW						30,000
Sun Edison Utility-Scale Solar and Wind
Business Acquisition [Line Items]
Cash consideration					$ 124
Purchase price					328
Current assets					5
Payments contingent upon future development milestones						$ 59
Amount paid for contingent consideration liability as of period end						20
SunEdison Solar Distributed Generation
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW			29
Cash consideration			$ 67
Purchase price allocated to construction in process			47
Purchase price allocated to intangible			15
Desert Sunlight
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW				550
Cash consideration				$ 285
Percentage of ownership interest				25.00%
Mechanically-complete Solar Assets \| Sun Edison Utility-Scale Solar and Wind
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW		530
In-development Wind Assets \| Sun Edison Utility-Scale Solar and Wind
Business Acquisition [Line Items]
Cash consideration		$ 111
Debt assumed					$ 222	$ 222
Remaining Lease Term					20 years
Construction-ready and in-development solar assets \| Sun Edison Utility-Scale Solar and Wind
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW						110
Cash consideration			2
In-development solar assets \| Sun Edison Utility-Scale Solar and Wind
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW						71
Construction-ready Solar Facility \| Sun Edison Utility-Scale Solar and Wind
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW						154
Cash consideration	$ 11
NRG \| Mechanically-complete Solar Assets \| Sun Edison Utility-Scale Solar and Wind
Business Acquisition [Line Items]
Generation capacity (in MW) \| MW		265
Post-closing obligations \| SunEdison Solar Distributed Generation
Business Acquisition [Line Items]
Cash consideration			$ 5
Non Recourse Debt \| Utah Portfolio
Business Acquisition [Line Items]
Additional debt borrowed					$ 65	$ 65