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Summary of Significant Accounting Policies - Pension Plan Contributions (Details) $ in Millions | Jun. 30, 2020 USD ($)
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Accounting Policies [Abstract] |
Pension plan employer contributions deferred until 2021 due to CARES Act | $ 47

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- Definition Defined Benefit Plan, Deferral of Future Employer Contributions due to CARES Act + References No definition available. + Details
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Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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