XML 116 R87.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Commitments and Contingencies, Environmental Contingencies - Unrecorded Unconditional Purchase Obligation (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) Plant
Clean Water Act Effluent Limitations Guidelines [Domain] |
Environmental Requirements [Abstract] |
Liability for Estimated Cost to Comply with Regulation | $ 12
PSCo | Federal Coal Ash Regulation [Domain] |
Unrecorded Unconditional Purchase Obligation [Line Items] |
Number of sites where statistically significant increases over established groundwater standards exist | 2
NSP-Minnesota | Federal Coal Ash Regulation [Domain] |
Unrecorded Unconditional Purchase Obligation [Line Items] |
Number of sites where SSI's have been identified | 1
NSP-Minnesota | Federal Clean Water Act Section 316(b) |
Environmental Requirements [Abstract] |
Minimum Number of Plants Which Could Be Required to Make Improvements to Reduce Entrainment | Plant | 6
NSP-Wisconsin | Federal Clean Water Act Section 316(b) |
Environmental Requirements [Abstract] |
Minimum Number of Plants Which Could Be Required to Make Improvements to Reduce Entrainment | Plant | 2
Capital Commitments | Federal Clean Water Act Section 316(b) |
Environmental Requirements [Abstract] |
Liability for Estimated Cost to Comply with Regulation | $ 40
Liability for Estimated Cost to Comply With Entrainment Regulation | $ 200
Harrington Units 1 and 2 | SPS | Implementation of the National Ambient Air Quality Standard for Sulfur Dioxide |
Environmental Requirements [Abstract] |
Number of Years Unclassifiable Areas Will Be Monitored | 3 years
Tolk Units 1 and 2 | Capital Commitments | SPS | Regional Haze Rules |
Environmental Requirements [Abstract] |
Liability for Estimated Cost to Comply with Regulation | $ 600

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

X
- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | xel_EnvironmentalRequirementsAbstract
Namespace Prefix: | xel_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Estimated undiscounted amount of the accrual required to comply with required regulation. + References No definition available. + Details
Name: | xel_LiabilityForEstimatedCostToComplyWithRegulation
Namespace Prefix: | xel_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Estimated undiscounted amount of the accrual required to comply with required entrainment regulation under the federal Clean Water Act Section 316(b) rule. + References No definition available. + Details
Name: | xel_Liabilityforestimatedcosttocomplywithentrainmentregulation
Namespace Prefix: | xel_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Minimum number of plants which could be required by state regulators to make improvements to reduce entrainment + References No definition available. + Details
Name: | xel_Minimumnumberofplantswhichcouldberequiredtomakeimprovementstoreduceentrainment
Namespace Prefix: | xel_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of impoundments where closure plans will be expedited + References No definition available. + Details
Name: | xel_Numberofimpoundmentswhereclosureplanswillbeexpedited
Namespace Prefix: | xel_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of sites where statistically significant increases over established groundwater standards exist + References No definition available. + Details
Name: | xel_Numberofsiteswherestatisticallysignificantincreasesoverestablishedgroundwaterstandardsexist
Namespace Prefix: | xel_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of years unclassifiable areas will be monitored + References No definition available. + Details
Name: | xel_Numberofyearsunclassifiableareaswillbemonitored
Namespace Prefix: | xel_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | xel_EnvironmentalRegulationAxis=xel_CleanWaterActEffluentLimitationsGuidelinesDomain
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=xel_PscoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | xel_EnvironmentalRegulationAxis=xel_FederalCoalAshRegulationDomain
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=xel_NspMinnesotaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | xel_EnvironmentalRegulationAxis=xel_FederalCleanWaterActSection316bMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=xel_NSPWisconsinMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_CapitalAdditionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | xel_AssociatedPlantAxis=xel_HarringtonUnits1and2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=xel_SpsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | xel_EnvironmentalRegulationAxis=xel_ImplementationoftheNationalAmbientAirQualityStandardforsulfurdioxideMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | xel_AssociatedPlantAxis=xel_TolkUnits1and2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | xel_EnvironmentalRegulationAxis=xel_RegionalHazeRulesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |