Projected Benefit Payments (Details) $ in Millions	Dec. 31, 2019 USD ($)
Pension Plan [Member]
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]
2020	$ 278
2021	263
2022	262
2023	260
2024	255
2025-2029	1,205
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]
2020	44
2021	43
2022	42
2023	41
2024	40
2025-2029	181
Expected Medicare Part D Subsidies [Abstract]
2020	2
2021	2
2022	2
2023	2
2024	2
2025-2029	13
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]
2020	42
2021	41
2022	40
2023	39
2024	38
2025-2029	$ 168

No definition available.

Name:	us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of prescription drug subsidy receipts expected after fifth fiscal year following latest fiscal year.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsAfterYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of prescription drug subsidy receipts expected in next fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of prescription drug subsidy receipts expected in fifth fiscal year following latest fiscal year.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

+ Details

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsYearFive1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of prescription drug subsidy receipts expected in fourth fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsYearFour1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of prescription drug subsidy receipts expected in third fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsYearThree1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of prescription drug subsidy receipts expected in second fiscal year following latest fiscal year.

+ References

+ Details

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsYearTwo1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

Name:	xel_DefinedBenefitPlanNetProjectedBenefitPaymentsAbstract
Namespace Prefix:	xel_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in the five fiscal years thereafter (the aggregate net amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

+ References

No definition available.

+ Details

Name:	xel_DefinedBenefitPlanNetProjectedBenefitPaymentsInFiveFiscalYearsThereafter
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 5 after the balance sheet date.

+ References

No definition available.

+ Details

Name:	xel_DefinedBenefitPlanNetProjectedBenefitPaymentsInYearFive
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 4 after the balance sheet date.

+ References

No definition available.

+ Details

Name:	xel_DefinedBenefitPlanNetProjectedBenefitPaymentsInYearFour
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 1 after the balance sheet date.

+ References

No definition available.

+ Details

Name:	xel_DefinedBenefitPlanNetProjectedBenefitPaymentsInYearOne
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 3 after the balance sheet date.

+ References

No definition available.

+ Details

Name:	xel_DefinedBenefitPlanNetProjectedBenefitPaymentsInYearThree
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 2 after the balance sheet date.

+ References

No definition available.

+ Details

Name:	xel_DefinedBenefitPlanNetProjectedBenefitPaymentsInYearTwo
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

Name:	xel_NetProjectedPostretirementHealthCareBenefitPaymentsAbstract
Namespace Prefix:	xel_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: