Borrowings and Other Financing Instruments Borrowings and Other Financing Instruments, Credit Facilities (Details)		12 Months Ended
		Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility		$ 3,250,000,000
Drawn	[1]	1,087,000,000
Available		$ 2,163,000,000
Xcel Energy Inc. | Credit Facilities
Line of Credit Facility [Line Items]
Line Of Credit Facility Debt To Total Capitalization Ratio (as a percent)	[2],[3]	58.00%	58.00%
Credit Facility	[4]	$ 1,500,000,000
Drawn	[1]	488,000,000
Available		1,012,000,000
Line Of Credit Facility Maximum Amount Credit Facility May Be Increased	[3]	$ 200,000,000
Line Of Credit Facility Maximum Debt To Total Capitalization Ratio Allowed		65.00%
Line Of Credit Facility Minimum Threshhold Percentage Of Subsidiary Assets To Consolidated Assets Required To Initiate Cross Default Provisions		15.00%
Line of Credit Facility, Minimum Amount of Indebtedness in Default to Initiate Cross Default Provisions		$ 75,000,000
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval	[3],[5]	2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
Debt Instrument, Maturity Date		Jun. 30, 2021
Direct advances on the credit facility outstanding			$ 0
Xcel Energy Inc. | 364-Day Term Loan
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Period		364 days
NSP-Minnesota | Credit Facilities
Line of Credit Facility [Line Items]
Line Of Credit Facility Debt To Total Capitalization Ratio (as a percent)	[2]	48.00%	48.00%
Credit Facility	[4]	$ 500,000,000
Drawn	[1]	187,000,000
Available		313,000,000
Line Of Credit Facility Maximum Amount Credit Facility May Be Increased		$ 100,000,000
Line Of Credit Facility Maximum Debt To Total Capitalization Ratio Allowed		65.00%
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval	[5]	2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
Direct advances on the credit facility outstanding		$ 0	$ 0
PSCo | Credit Facilities
Line of Credit Facility [Line Items]
Line Of Credit Facility Debt To Total Capitalization Ratio (as a percent)	[2]	46.00%	44.00%
Credit Facility	[4]	$ 700,000,000
Drawn	[1]	317,000,000
Available		383,000,000
Line Of Credit Facility Maximum Amount Credit Facility May Be Increased		$ 100,000,000
Line Of Credit Facility Maximum Debt To Total Capitalization Ratio Allowed		65.00%
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval	[5]	2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
Direct advances on the credit facility outstanding		$ 0	$ 0
SPS | Credit Facilities
Line of Credit Facility [Line Items]
Line Of Credit Facility Debt To Total Capitalization Ratio (as a percent)	[2]	46.00%	46.00%
Credit Facility	[4]	$ 400,000,000
Drawn	[1]	44,000,000
Available		356,000,000
Line Of Credit Facility Maximum Amount Credit Facility May Be Increased		$ 50,000,000
Line Of Credit Facility Maximum Debt To Total Capitalization Ratio Allowed		65.00%
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval	[5]	2
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
Direct advances on the credit facility outstanding		$ 0	$ 0
NSP-Wisconsin | Credit Facilities
Line of Credit Facility [Line Items]
Line Of Credit Facility Debt To Total Capitalization Ratio (as a percent)	[2]	48.00%	47.00%
Credit Facility	[4]	$ 150,000,000
Drawn	[1]	51,000,000
Available		$ 99,000,000
Line Of Credit Facility Maximum Debt To Total Capitalization Ratio Allowed		65.00%
Number Of Additional Periods Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval	[5]	1
Term Of Each Additional Period Revolving Termination Date Can Be Extended Subject To Majority Bank Group Approval		1 year
Direct advances on the credit facility outstanding		$ 0	$ 0

[1] Includes outstanding commercial paper, term loan borrowings and letters of credit.

[2] Each credit facility has a financial covenant requiring that the debt-to-total capitalization ratio be less than or equal to 65%.

[3] The Xcel Energy Inc. credit facility has a cross-default provision that Xcel Energy Inc. will be in default on its borrowings under the facility if it or any of its subsidiaries (except NSP-Wisconsin as long as its total assets do not comprise more than 15% of Xcel Energy’s consolidated total assets) default on indebtedness in an aggregate principal amount exceeding $75 million.

[4] These credit facilities mature in June 2021, with the exception of Xcel Energy’s Inc.’s 364-day term loan agreement which expires in December 2019.

[5] All extension requests are subject to majority bank group approval.