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Basis of Presentation - Basis of Presentation (Details) | Mar. 31, 2018 MW
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Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Generation capacity (in MW) | 30,000

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- Definition The generation capacity of the entity's power generation facilities as of the balance sheet date, expressed in megawatts. + References No definition available. + Details
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Namespace Prefix: | nrg_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration