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Variable Interest Entities (Details) - MW | Sep. 30, 2021 | Dec. 31, 2020
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Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member] |  |
Variable Interest Entity [Line Items] |  |
Generating capacity under long term purchased power agreements (in MW) | 4,062 | 4,062

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- 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
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration

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- Definition Generating capacity under long-term purchased power agreements. + References No definition available. + Details
Name: | xel_GeneratingCapacityUnderLongTermPurchasedPowerAgreements
Namespace Prefix: | xel_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

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