Line of Credit Facility, Maximum Borrowing Capacity, Increase

No definition available.

Name:	nrg_LineOfCreditFacilityMaximumBorrowingCapacityIncrease
Namespace Prefix:	nrg_
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=nrg_CreditAgreement2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

Long-term Debt and Finance Leases -Senior Credit Facility, Credit Default Swap Facility and Bilateral letter of Credit Facilities (Details) - USD ($)		3 Months Ended	12 Months Ended
	Jan. 04, 2019	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2021
Credit Agreement 2019 \| Letter of Credit
Debt Instrument [Line Items]
Increase in revolving commitments and letters of credit			$ 150,000,000
Revolving credit facility	$ 80,000,000
Annual facility fees, percentage	1.33%
Letter of credit				$ 222,000,000
Bilateral letter of credit facilities \| Letter of Credit
Debt Instrument [Line Items]
Revolving credit facility			475,000,000
Letter of credit				469,000,000
Bilateral letter of credit facilities \| Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility			$ 475,000,000
Line of Credit \| Credit Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Increase in revolving commitments and letters of credit		$ 802,000,000
Revolving credit facility		$ 273,000,000
Revolving commitments available				$ 3,700,000,000