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v3.8.0.1

Guarantees (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Guarantor Obligations |  |
Under 1 Year | $ 1,467 |
1-3 Years | 98 |
3-5 Years | 264 |
Over 5 Years | 761 |
Guarantees by Remaining Maturity, Total | 2,590 | $ 2,767
Letters of credit and surety bonds |  |
Guarantor Obligations |  |
Under 1 Year | 1,467 |
1-3 Years | 66 |
3-5 Years | 7 |
Over 5 Years | 93 |
Guarantees by Remaining Maturity, Total | $ 1,633 | 1,837
Letters of credit and surety bonds, maximum expiration period (in years) | 1 year |
Asset sales guarantee obligations |  |
Guarantor Obligations |  |
Under 1 Year | $ 0 |
1-3 Years | 0 |
3-5 Years | 257 |
Over 5 Years | 55 |
Guarantees by Remaining Maturity, Total | 312 | 677
Other guarantees |  |
Guarantor Obligations |  |
Under 1 Year | 0 |
1-3 Years | 32 |
3-5 Years | 0 |
Over 5 Years | 613 |
Guarantees by Remaining Maturity, Total | 645 | 253
Eliminations | Letters of credit and surety bonds |  |
Guarantor Obligations |  |
Guarantees by Remaining Maturity, Total | $ 92 | $ 272

X
- Definition Maximum potential amount of future payments that the guarantor could be required to make between one to three years of the balance sheet date under the guarantee. + References No definition available. + Details
Name: | nrg_GuaranteeMaturityBetweenOneToThreeYears
Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum potential amount of future payments that the guarantor could be required to make between three to five years of the balance sheet date under the guarantee. + References No definition available. + Details
Name: | nrg_GuaranteeMaturityBetweenThreeToFiveYears
Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum potential amount of future payments that the guarantor could be required to make after five years of the balance sheet date under the guarantee. + References No definition available. + Details
Name: | nrg_GuaranteeMaturityGreaterThanFiveYears
Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Maximum potential amount of future payments that the guarantor could be required to make within one year of the balance sheet date under the guarantee. + References No definition available. + Details
Name: | nrg_GuaranteeMaturityLessThanOneYear
Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The estimated amount of future payments the guarantor could be required to make under guarantees, indemnities and other contingent liability obligations. + References No definition available. + Details
Name: | nrg_GuaranteeObligationsEstimatedExposure
Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This element represents the maximum expiration period of letters of credit and surety bonds for entity is contingently obliged. + References No definition available. + Details
Name: | nrg_GuaranteeObligationsLettersofCreditandSuretyBondsMaximumExpirationPeriod
Namespace Prefix: | nrg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- 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_GuaranteeObligationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=nrg_LettersOfCreditAndSuretyBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=nrg_AssetSalesGuaranteeObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_GuaranteeTypeOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_ConsolidationItemsAxis=us-gaap_ConsolidationEliminationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |