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CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) - $ / shares
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Common Stockholders' Equity    
Common stock, shares authorized (in shares) 1,000,000,000 1,000,000,000
Common stock, par value (in dollars per share) $ 2.50 $ 2.50
Common stock, shares outstanding (in shares) 507,222,795 507,535,523
NSP-Minnesota | First Mortgage Bonds | Series Due March 1, 2018    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.25% 5.25%
Debt instrument, maturity date Mar. 01, 2018 Mar. 01, 2018
NSP-Minnesota | First Mortgage Bonds | Series Due Aug. 15, 2020    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.20% 2.20%
Debt instrument, maturity date Aug. 15, 2020 Aug. 15, 2020
NSP-Minnesota | First Mortgage Bonds | Series Due Aug. 15, 2022    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.15% 2.15%
Debt instrument, maturity date Aug. 15, 2022 Aug. 15, 2022
NSP-Minnesota | First Mortgage Bonds | Series Due May 15, 2023    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.60% 2.60%
Debt instrument, maturity date May 15, 2023 May 15, 2023
NSP-Minnesota | First Mortgage Bonds | Series Due July 1, 2025    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 7.125% 7.125%
Debt instrument, maturity date Jul. 01, 2025 Jul. 01, 2025
NSP-Minnesota | First Mortgage Bonds | Series Due March 1, 2028    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.50% 6.50%
Debt instrument, maturity date Mar. 01, 2028 Mar. 01, 2028
NSP-Minnesota | First Mortgage Bonds | Series Due July 15, 2035    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.25% 5.25%
Debt instrument, maturity date Jul. 15, 2035 Jul. 15, 2035
NSP-Minnesota | First Mortgage Bonds | Series Due June 1, 2036    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.25% 6.25%
Debt instrument, maturity date Jun. 01, 2036 Jun. 01, 2036
NSP-Minnesota | First Mortgage Bonds | Series Due July 1, 2037    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.20% 6.20%
Debt instrument, maturity date Jul. 01, 2037 Jul. 01, 2037
NSP-Minnesota | First Mortgage Bonds | Series Due Nov. 1, 2039    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.35% 5.35%
Debt instrument, maturity date Nov. 01, 2039 Nov. 01, 2039
NSP-Minnesota | First Mortgage Bonds | Series Due Aug. 15, 2040    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.85% 4.85%
Debt instrument, maturity date Aug. 15, 2040 Aug. 15, 2040
NSP-Minnesota | First Mortgage Bonds | Series Due Aug. 15, 2042    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.40% 3.40%
Debt instrument, maturity date Aug. 15, 2042 Aug. 15, 2042
NSP-Minnesota | First Mortgage Bonds | Series Due May 15, 2044    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.125% 4.125%
Debt instrument, maturity date May 15, 2044 May 15, 2044
NSP-Minnesota | First Mortgage Bonds | Series Due Aug. 15, 2045    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.00% 4.00%
Debt instrument, maturity date Aug. 15, 2045 Aug. 15, 2045
NSP-Minnesota | First Mortgage Bonds | Series Due May 15, 2046 [Member]    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.60%  
Debt instrument, maturity date May 15, 2046  
PSCo | First Mortgage Bonds | Series Due Sept. 1, 2017    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage [1] 4.375% 4.375%
Debt instrument, maturity date [1] Sep. 01, 2017 Sep. 01, 2017
PSCo | First Mortgage Bonds | Series Due Aug. 1, 2018    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.80% 5.80%
Debt instrument, maturity date Aug. 01, 2018 Aug. 01, 2018
PSCo | First Mortgage Bonds | Series Due June 1, 2019    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.125% 5.125%
Debt instrument, maturity date Jun. 01, 2019 Jun. 01, 2019
PSCo | First Mortgage Bonds | Series Due Nov. 15, 2020    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.20% 3.20%
Debt instrument, maturity date Nov. 15, 2020 Nov. 15, 2020
PSCo | First Mortgage Bonds | Series Due Sept. 15, 2022    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.25% 2.25%
Debt instrument, maturity date Sep. 15, 2022 Sep. 15, 2022
PSCo | First Mortgage Bonds | Series Due March 15, 2023    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.50% 2.50%
Debt instrument, maturity date Mar. 15, 2023 Mar. 15, 2023
PSCo | First Mortgage Bonds | Series Due May 15, 2025    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.90% 2.90%
Debt instrument, maturity date May 15, 2025 May 15, 2025
PSCo | First Mortgage Bonds | Series Due Sept. 1, 2037    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.25% 6.25%
Debt instrument, maturity date Sep. 01, 2037 Sep. 01, 2037
PSCo | First Mortgage Bonds | Series Due Aug. 1, 2038    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.50% 6.50%
Debt instrument, maturity date Aug. 01, 2038 Aug. 01, 2038
PSCo | First Mortgage Bonds | Series Due Aug. 15, 2041    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.75% 4.75%
Debt instrument, maturity date Aug. 15, 2041 Aug. 15, 2041
PSCo | First Mortgage Bonds | Series Due Sept. 15, 2042    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.60% 3.60%
Debt instrument, maturity date Sep. 15, 2042 Sep. 15, 2042
PSCo | First Mortgage Bonds | Series Due March 15, 2043    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.95% 3.95%
Debt instrument, maturity date Mar. 15, 2043 Mar. 15, 2043
PSCo | First Mortgage Bonds | Series Due March 15, 2044    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.30% 4.30%
Debt instrument, maturity date Mar. 15, 2044 Mar. 15, 2044
PSCo | First Mortgage Bonds | Series Due June 15, 2046 [Member]    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.55% 3.55%
Debt instrument, maturity date Jun. 15, 2046 Jun. 15, 2046
PSCo | Capital Lease Obligations    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt Instrument, Maturity Date Range, End Dec. 31, 2060  
PSCo | Capital Lease Obligations | Minimum    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 11.20%  
PSCo | Capital Lease Obligations | Maximum    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 14.30%  
SPS | First Mortgage Bonds | Series Due Aug. 15, 2041    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.50% 4.50%
Debt instrument, maturity date Aug. 15, 2041 Aug. 15, 2041
SPS | First Mortgage Bonds | Series Due June 15, 2024    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.30% 3.30%
Debt instrument, maturity date Jun. 15, 2024 Jun. 15, 2024
SPS | First Mortgage Bonds | Series Due Aug. 15, 2046 [Member]    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.40%  
Debt instrument, maturity date Aug. 15, 2046  
SPS | Senior Unsecured Notes | Senior E Due Oct. 1, 2016    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.60% 5.60%
Debt instrument, maturity date Oct. 01, 2016 Oct. 01, 2016
SPS | Senior Unsecured Notes | Senior G Due Dec. 1, 2018    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 8.75% 8.75%
Debt instrument, maturity date Dec. 01, 2018 Dec. 01, 2018
SPS | Senior Unsecured Notes | Senior C and D Due Oct. 1, 2033    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.00% 6.00%
Debt instrument, maturity date Oct. 01, 2033 Oct. 01, 2033
SPS | Senior Unsecured Notes | Senior F Due Oct. 1, 2036    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.00% 6.00%
Debt instrument, maturity date Oct. 01, 2036 Oct. 01, 2036
NSP-Wisconsin | First Mortgage Bonds | Series Due Oct. 1, 2018    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.25% 5.25%
Debt instrument, maturity date Oct. 01, 2018 Oct. 01, 2018
NSP-Wisconsin | First Mortgage Bonds | Series Due June 15, 2024    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.30% 3.30%
Debt instrument, maturity date Jun. 15, 2024 Jun. 15, 2024
NSP-Wisconsin | First Mortgage Bonds | Series Due Sept. 1, 2038    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.375% 6.375%
Debt instrument, maturity date Sep. 01, 2038 Sep. 01, 2038
NSP-Wisconsin | First Mortgage Bonds | Series Due Oct. 1, 2042    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.70% 3.70%
Debt instrument, maturity date Oct. 01, 2042 Oct. 01, 2042
NSP-Wisconsin | City of La Crosse Resource Recovery Bond | Series Due Nov. 1, 2021    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage [2] 6.00% 6.00%
Debt instrument, maturity date [2] Nov. 01, 2021 Nov. 01, 2021
NSP-Wisconsin | Fort McCoy System Acquisition | Due Oct. 15, 2030    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 7.00% 7.00%
Debt instrument, maturity date Oct. 15, 2030 Oct. 15, 2030
Other Subsidiaries | Various Eloigne Co. Affordable Housing Project Notes | Due 2017-2052    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt Instrument, Maturity Date Range, Start Jan. 01, 2017  
Debt Instrument, Maturity Date Range, End Dec. 31, 2052  
Other Subsidiaries | Various Eloigne Co. Affordable Housing Project Notes | Due 2017-2052 | Minimum    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 0.00%  
Other Subsidiaries | Various Eloigne Co. Affordable Housing Project Notes | Due 2017-2052 | Maximum    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 7.05%  
Xcel Energy Inc.    
Common Stockholders' Equity    
Common stock, shares outstanding (in shares) 507,222,795 507,535,523
Xcel Energy Inc. | Senior Unsecured Notes | Series Due May 9, 2016    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 0.75% 0.75%
Debt instrument, maturity date May 09, 2016 May 09, 2016
Xcel Energy Inc. | Senior Unsecured Notes | Series Due April 1, 2017    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 5.613% 5.613%
Debt instrument, maturity date Apr. 01, 2017 Apr. 01, 2017
Xcel Energy Inc. | Senior Unsecured Notes | Series Due June 1, 2017    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 1.20% 1.20%
Debt instrument, maturity date Jun. 01, 2017 Jun. 01, 2017
Xcel Energy Inc. | Senior Unsecured Notes | Series Due May 15, 2020    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.70% 4.70%
Debt instrument, maturity date May 15, 2020 May 15, 2020
Xcel Energy Inc. | Senior Unsecured Notes | Series Due March 15, 2021 [Member]    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.40%  
Debt instrument, maturity date Mar. 15, 2021  
Xcel Energy Inc. | Senior Unsecured Notes | Series Due March 15, 2022 [Member]    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 2.60%  
Debt instrument, maturity date Mar. 15, 2022  
Xcel Energy Inc. | Senior Unsecured Notes | Series Due June 1, 2025    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.30% 3.30%
Debt instrument, maturity date Jun. 01, 2025 Jun. 01, 2025
Xcel Energy Inc. | Senior Unsecured Notes | Series Due Dec. 1, 2026 [Member]    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 3.35%  
Debt instrument, maturity date Dec. 01, 2026  
Xcel Energy Inc. | Senior Unsecured Notes | Series Due July 1, 2036    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 6.50% 6.50%
Debt instrument, maturity date Jul. 01, 2036 Jul. 01, 2036
Xcel Energy Inc. | Senior Unsecured Notes | Series Due Sept. 15, 2041    
Schedule of Capitalization, Long-term Debt [Line Items]    
Debt instrument, interest rate, stated percentage 4.80% 4.80%
Debt instrument, maturity date Sep. 15, 2041 Sep. 15, 2041
[1] Pollution control financing.
[2] Resource recovery financing.