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Goodwill and Other Intangibles - Out of Market Contracts (Details) - Out of Market Contracts - Lease Agreements $ in Millions | 12 Months Ended
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Dec. 31, 2018 USD ($)
Out of Market Contracts Five Year Maturity |
2019 | $ 8
2020 | 8
2021 | 8
2022 | 8
2023 | $ 8

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- Definition The amount of amortization for out-of-market contracts expected to be recognized during the fifth twelve-month period following the balance sheet date. + References No definition available. + Details
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Balance Type: | debit
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- Definition The amount of amortization for out-of-market contracts expected to be recognized during the fourth twelve-month period following the balance sheet date. + References No definition available. + Details
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Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
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X
- Definition The amount of amortization for out-of-market contracts expected to be recognized during the twelve-month period following the balance sheet date. + References No definition available. + Details
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- Definition The amount of amortization for out-of-market contracts expected to be recognized during the third twelve-month period following the balance sheet date. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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X
- Definition The amount of amortization for out-of-market contracts expected to be recognized during the second twelve-month period following the balance sheet date. + References No definition available. + Details
Name: | nrg_FutureAmortizationExpensesOutOfMarketContractsYearTwo
Namespace Prefix: | nrg_
Data Type: | xbrli:monetaryItemType
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- Definition Out of Market Contract Five Year Maturity + References No definition available. + Details
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Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
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- Details
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Data Type: | na
Balance Type: |
Period Type: |