This element represents the exercise price under employee stock purchase plan as a percentage of fair value.

No definition available.

Name:	nrg_EmployeeStockPurchasePlanExercisePriceAsPercentageOfFairValue
Namespace Prefix:	nrg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the maximum percentage of eligible compensation, which can be withheld by employees to purchase shares of the entity.

+ References

No definition available.

+ Details

Name:	nrg_EmployeeStockPurchasePlanMaximumPercentageOfCompensationEligible
Namespace Prefix:	nrg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Employee Stock Purchase Plan, Minimum Percentage of Compensation Eligible

+ References

No definition available.

+ Details

Name:	nrg_EmployeeStockPurchasePlanMinimumPercentageofCompensationEligible
Namespace Prefix:	nrg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Long-term Capital Allocation, Target Allocation, Cash Generated Allocated Returned to Shareholders, Percentage

+ References

No definition available.

+ Details

Name:	nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedReturnedToShareholdersPercentage
Namespace Prefix:	nrg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Long-term Capital Allocation, Target Allocation, Cash Generated Allocated to Growth Investments, Percentage

+ References

No definition available.

+ Details

Name:	nrg_LongTermCapitalAllocationTargetAllocationCashGeneratedAllocatedToGrowthInvestmentsPercentage
Namespace Prefix:	nrg_
Data Type:	dtr-types:percentItemType
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_ClassOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ 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(28))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 4: 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(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

+ Details

Name:	us-gaap_TreasuryStockAcquiredAverageCostPerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	nrg_CapitalAllocationPlanAxis=nrg_CapitalAllocationPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nrg_CapitalAllocationPlanAxis=nrg_CapitalAllocationPlanOpenMarketRepurchasesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Changes in Capital Structure - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2022	Dec. 31, 2019	Dec. 31, 2021	Dec. 06, 2021
Class of Stock [Line Items]
Long-term capital allocation, target allocation, cash generated allocated to growth investments, percentage			50.00%
Long-term capital allocation, target allocation, cash generated allocated returned to shareholders, percentage			50.00%
ESPP, minimum percentage of eligible compensation to purchase shares	1.00%
ESPP, maximum percentage of eligible compensation	10.00%
ESPP, exercise price as percentage of fair value	95.00%
Capital Allocation Plan
Class of Stock [Line Items]
Stock repurchase program, authorized amount					$ 1,000,000,000
Amounts paid for shares purchased		$ 193,000,000		$ 44,000,000
Average price paid per share (in usd per share)		$ 38.78
Capital Allocation Plan, Open Market Repurchases
Class of Stock [Line Items]
Amounts paid for shares purchased		$ 187,000,000
Average price paid per share (in usd per share)		$ 38.66