Net increase or decrease in the carrying amount of the debt instrument for the period.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Name:	us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

Acquisitions, Discontinued Operations and Dispositions -Collective Collateral Facilities (Details) - USD ($)	Jan. 05, 2021	Jul. 26, 2021	Dec. 31, 2020
Direct Energy
Line of Credit Facility [Line Items]
Revolving credit facility commitment increase	$ 3,400,000,000
Revolving Credit Facility \| Revolving Credit Facility commitment increase
Line of Credit Facility [Line Items]
Revolving credit facility commitment increase	802,000,000
Revolving Credit Facility \| Revolving Credit Facility new tranche
Line of Credit Facility [Line Items]
Revolving credit facilities	273,000,000
Revolving Credit Facility \| Facility agreement in connection with the sale of pre-capitalized trust securities
Line of Credit Facility [Line Items]
Revolving credit facilities	874,000,000
Revolving Credit Facility \| Credit default swap facility
Line of Credit Facility [Line Items]
Revolving credit facilities			$ 150,000,000
Revolving Credit Facility \| Revolving accounts receivable financing facility
Line of Credit Facility [Line Items]
Revolving credit facilities		$ 800,000,000	750,000,000
Revolving Credit Facility \| Repurchase facility
Line of Credit Facility [Line Items]
Revolving credit facilities			75,000,000
Revolving Credit Facility \| Bilateral letter of credit facilities
Line of Credit Facility [Line Items]
Revolving credit facilities			$ 475,000,000
Revolving Credit Facility \| Total Increases to Liquidity and Collateral Facilities
Line of Credit Facility [Line Items]
Revolving credit facility commitment increase	$ 3,399,000,000