Revenues (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Total revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 11,032	$ 11,020
Total revenue from contracts with customers \| Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	9,144	9,339
Total revenue from contracts with customers \| Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,814	1,612
Total revenue from contracts with customers \| All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	74	69
Retail
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	9,619	9,508
Retail \| Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,045	3,945
Retail \| C&I
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,440	5,423
Retail \| Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	134	140
Retail \| Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	7,851	7,927
Retail \| Regulated Electric \| Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,877	2,919
Retail \| Regulated Electric \| C&I
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,844	4,874
Retail \| Regulated Electric \| Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	130	134
Retail \| Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,694	1,512
Retail \| Natural Gas \| Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,127	988
Retail \| Natural Gas \| C&I
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	567	524
Retail \| Natural Gas \| Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Retail \| All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	74	69
Retail \| All Other \| Residential
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	41	38
Retail \| All Other \| C&I
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	29	25
Retail \| All Other \| Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4	6
Wholesale
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	737	791
Wholesale \| Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	737	791
Wholesale \| Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Wholesale \| All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Transmission
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	507	523
Transmission \| Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	507	523
Transmission \| Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Transmission \| All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	169	198
Other \| Regulated Electric
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	49	98
Other \| Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	120	100
Other \| All Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0
Alternative revenue and other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	497	517
Alternative revenue and other \| Regulated Electric
Disaggregation of Revenue [Line Items]
Alternative revenue and other	431	380
Alternative revenue and other \| Natural Gas
Disaggregation of Revenue [Line Items]
Alternative revenue and other	54	127
Alternative revenue and other \| All Other
Disaggregation of Revenue [Line Items]
Alternative revenue and other	12	10
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	11,529	11,537
Operating Segments \| Regulated Electric
Disaggregation of Revenue [Line Items]
Total revenues	9,575	9,719
Operating Segments \| Natural Gas
Disaggregation of Revenue [Line Items]
Total revenues	1,868	1,739
Operating Segments \| All Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 86	$ 79

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.

No definition available.

+ Details

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

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

+ Details

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue that is not accounted for under Topic 606.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

Name:	us-gaap_RevenueNotFromContractWithCustomer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_ProductMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=xel_RegulatedElectricMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=xel_RegulatedNaturalGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_AllOtherSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=xel_RetailDistributionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MajorCustomersAxis=xel_ResidentialCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MajorCustomersAxis=xel_CommercialandIndustrialCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MajorCustomersAxis=xel_OtherCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=xel_WholesaleDistributionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=xel_TransmissionServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=xel_OtherServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=xel_AlternativeandOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: