The amount of credit exposure to a significant portion of all counterparties.

No definition available.

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

- Definition

Carrying amount as of the balance sheet date of cash collateral and letters of credit received by the entity on deposit from third parties in support of energy risk management.

+ References

No definition available.

+ Details

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

- Definition

The percentage of net counterparty credit exposure that rolls-off by the end of 2012.

+ References

No definition available.

+ Details

Name:	nrg_CounterpartyCreditRiskExposurePercentageOfCreditRiskRollOff
Namespace Prefix:	nrg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the threshold percentage for disclosure of counterparty credit exposure.

+ References

No definition available.

+ Details

Name:	nrg_CounterpartyCreditRiskExposurePercentageThreshold
Namespace Prefix:	nrg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of net counterparty credit exposure of the entity.

+ References

No definition available.

+ Details

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

- Definition

This element represents the estimated amount of the counterparty credit risk exposure.

+ References

No definition available.

+ Details

Name:	nrg_EstimatedCounterpartyCreditRiskExposureToCertainCounterparties
Namespace Prefix:	nrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Estimated Counterparty Credit Risk Exposure to Certain Counterparties, Period

+ References

No definition available.

+ Details

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

- Definition

Represents the net exposure of the entity determined as total credit exposure to all counterparties less collateral (cash and letters of credit) held against those positions as of the reporting date.

+ References

No definition available.

+ Details

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

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

- Definition

Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.5)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130534-203044

+ Details

Name:	us-gaap_ProvisionForDoubtfulAccounts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	nrg_CounterpartyRiskByInvestmentGradeAxis=us-gaap_ExternalCreditRatingInvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nrg_CounterpartyRiskByInvestmentGradeAxis=nrg_ExternalCreditRatingNotRatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nrg_CounterpartyRiskByInstitutionAxis=nrg_FinancialInstitutionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nrg_CounterpartyRiskByInstitutionAxis=nrg_UtilitiesEnergyMerchantsMarketersAndOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Fair Value of Financial Instruments - Counterparty Credit Risk (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Fair Value Meaurements and Concentration of Credit Risk
Counterparty credit exposure, excluding credit risk exposure under certain long term agreements	$ 301
Counterparty credit exposure, collateral held (cash and letters of credit) against positions	123
Counterparty credit exposure, net	$ 180
Company's exposure before collateral expected to roll off by the end of 2015 (as a percent)	66.00%
Net exposure (as a percent)	100.00%
Counterparty credit risk exposure to certain counterparties, threshold (as a percent)	10.00%
Estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements for the next 5 years	$ 434
Period of estimated counterparty credit risk exposure under certain long term agreements, including California tolling agreements, South Central load obligations and solar power purchase agreements (in years)	5 years
Provision for bad debts	$ 85	$ 68	$ 45
Non-Investment grade/Non-Rated
Derivative Fair Value Meaurements and Concentration of Credit Risk
Net exposure (as a percent)	51.00%
Investment grade
Derivative Fair Value Meaurements and Concentration of Credit Risk
Net exposure (as a percent)	49.00%
Financial Institutions
Derivative Fair Value Meaurements and Concentration of Credit Risk
Net exposure (as a percent)	89.00%
Financial institutions
Derivative Fair Value Meaurements and Concentration of Credit Risk
Net exposure (as a percent)	11.00%