XML 57 R60.htm IDEA: XBRL DOCUMENT
v3.20.1

Nuclear Decommissioning Trust Fund - Summary of aggregate fair values and realized gains and losses (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 | Dec. 31, 2019
Nuclear decommissioning trust fund |  |
Fair Value | $ 702 | $ 794
Unrealized Gains | 248 | 338
Unrealized Losses | 6 | 1
Cash and cash equivalents |  |
Nuclear decommissioning trust fund |  |
Fair Value | 21 | 17
Unrealized Gains | 0 | 0
Unrealized Losses | 0 | 0
U.S. government and federal agency obligations |  |
Nuclear decommissioning trust fund |  |
Fair Value | 57 | 68
Unrealized Gains | 10 | 4
Unrealized Losses | $ 0 | $ 0
Weighted-average Maturities (In years) | 14 years | 11 years
Federal agency mortgage-backed securities |  |
Nuclear decommissioning trust fund |  |
Fair Value | $ 93 | $ 100
Unrealized Gains | 4 | 3
Unrealized Losses | $ 0 | $ 0
Weighted-average Maturities (In years) | 24 years | 24 years
Commercial mortgage-backed securities |  |
Nuclear decommissioning trust fund |  |
Fair Value | $ 33 | $ 29
Unrealized Gains | 1 | 1
Unrealized Losses | $ 1 | $ 1
Weighted-average Maturities (In years) | 26 years | 24 years
Corporate debt securities |  |
Nuclear decommissioning trust fund |  |
Fair Value | $ 125 | $ 109
Unrealized Gains | 5 | 6
Unrealized Losses | $ 4 | $ 0
Weighted-average Maturities (In years) | 12 years | 11 years
Equity securities |  |
Nuclear decommissioning trust fund |  |
Fair Value | $ 368 | $ 466
Unrealized Gains | 228 | 324
Unrealized Losses | 1 | 0
Foreign government fixed income securities |  |
Nuclear decommissioning trust fund |  |
Fair Value | 5 | 5
Unrealized Gains | 0 | 0
Unrealized Losses | $ 0 | $ 0
Weighted-average Maturities (In years) | 10 years | 10 years

X
- Definition The weighted-average maturity period for securities of nuclear decommissioning trust funds assets. + References No definition available. + Details
Name: | nrg_DecommissioningTrustAssetsWeightedAverageMaturityPeriod
Namespace Prefix: | nrg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
Name: | us-gaap_DecommissioningTrustAssetsAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |