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Benefit Plans and Other Postretirement Benefits (Details) (USD $)
 1 Months Ended 12 Months Ended
Jan. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Employees Represented by Local Labor Unions Under Collective Bargaining Agreements Receiving Benefits [Abstract]        
Approximate percent of employees receiving benefits who are represented by local labor unions under collective bargaining agreements (in hundredths)   50.00%    
Funded Status of Plans at Dec. 31 [Abstract]        
Noncurrent liabilities   $ (1,001,906,000) $ (962,767,000)  
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]        
Number of employers that must be exceeded during a given period in order for certain union workers to participate in multiemployer plans   1    
Defined Contribution Plans [Abstract]        
Contributions to 401(k) and other defined contribution plans   27,100,000 27,300,000 21,900,000
Pension Benefits [Member]
        
Pension Benefits [Abstract]        
Minimum number of years historical achieved weighted average annual returns are used to determine overall expected return on asset portfolio (in years)   20Y    
Historical weighted average annual return for past 20 years for portfolio of pension investments (in hundredths)   8.73%    
Expected average long-term rate of return on assets for next fiscal year (in hundredths)   7.10%    
Target Pension Asset Allocations [Abstract]        
Domestic and international equity securities (in hundredths)   27.00% 24.00%  
Long-duration fixed income securities (in hundredths)   31.00% 41.00%  
Short-to-intermediate fixed income securities (in hundredths)   12.00% 11.00%  
Alternative investments (in hundredths)   27.00% 17.00%  
Cash (in hundredths)   3.00% 7.00%  
Total (in hundredths)   100.00% 100.00%  
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   2,670,280,000 2,540,708,000 2,449,326,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1 2,670,280,000 2,540,708,000 2,449,326,000  
Fair value of plan assets at Dec. 31   2,670,280,000 2,540,708,000 2,449,326,000
Accumulated Benefit Obligation at Dec. 31   3,073,637,000 2,865,845,000  
Change in Projected Benefit Obligation [Roll Forward]        
Obligation at Jan. 1 3,226,219,000 3,030,292,000 2,829,631,000  
Service cost   77,319,000 73,147,000 65,461,000
Interest cost   161,412,000 165,010,000 169,790,000
Plan amendments   0 18,739,000  
Actuarial loss   195,369,000 169,203,000  
Benefit payments   (238,173,000) (225,438,000)  
Obligation at Dec. 31   3,226,219,000 3,030,292,000 2,829,631,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1 2,670,280,000 2,540,708,000 2,449,326,000  
Actual return on plan assets   230,401,000 282,688,000  
Employer contributions   137,344,000 34,132,000  
Benefit payments   (238,173,000) (225,438,000)  
Fair value of plan assets at Dec. 31   2,670,280,000 2,540,708,000 2,449,326,000
Funded Status of Plans at Dec. 31 [Abstract]        
Funded status   (555,939,000) [1] (489,584,000) [1]  
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]        
Net loss   1,610,946,000 1,502,888,000  
Prior service cost (credit)   18,432,000 40,965,000  
Total   1,629,378,000 1,543,853,000  
Amounts Related to the Funded Status of the Plans Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]        
Current regulatory assets   123,814,000 92,765,000  
Noncurrent regulatory assets   1,435,372,000 1,386,125,000  
Deferred income taxes   28,759,000 26,592,000  
Net-of-tax accumulated other comprehensive income   41,433,000 38,371,000  
Total   1,629,378,000 1,543,853,000  
Measurement date   Dec. 31, 2011 Dec. 31, 2010  
Significant Assumptions Used to Measure Benefit Obligations [Abstract]        
Discount rate for year-end valuation (in hundredths)   5.00% 5.50%  
Expected average long-term increase in compensation level (in hundredths)   4.00% 4.00%  
Mortality table   RP 2000 RP 2000  
Significant Assumptions Used to Measure Costs [Abstract]        
Discount rate (in hundredths)   5.50% 6.00% 6.75%
Expected average long-term increase in compensation level (in hundredths)   4.00% 4.00% 4.00%
Expected average long-term rate of return on assets (in hundredths)   7.50% 7.79% 8.50%
Cash Flows [Abstract]        
Total contributions to Xcel Energy's pension plans during the period 190,500,000 137,300,000 34,000,000  
Number of pension plans to which contributions were made 4 3    
Components of Net Periodic Benefit Cost (Credit) [Abstract]        
Service cost   77,319,000 73,147,000 65,461,000
Interest cost   161,412,000 165,010,000 169,790,000
Expected return on plan assets   (221,600,000) (232,318,000) (256,538,000)
Amortization of prior service cost   22,533,000 20,657,000 24,618,000
Amortization of net loss   78,510,000 48,315,000 12,455,000
Net periodic benefit cost (credit)   118,174,000 74,811,000 15,786,000
(Costs) credits not recognized due to effects of regulation   (37,198,000) (27,027,000) (2,891,000)
Net benefit cost (credit) recognized for financial reporting   80,976,000 47,784,000 12,895,000
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]        
2012   270,101,000    
2013   253,333,000    
2014   261,854,000    
2015   263,129,000    
2016   264,885,000    
2017-2021   1,328,001,000    
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]        
Multiemployer contributions   17,980,000 13,631,000 11,464,000
Pension Benefits [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   216,143,000 240,542,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   216,143,000 240,542,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   216,143,000 240,542,000  
Pension Benefits [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   2,152,778,000 1,963,838,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   2,152,778,000 1,963,838,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   2,152,778,000 1,963,838,000  
Pension Benefits [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   301,359,000 336,328,000 340,633,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   336,328,000 340,633,000 434,331,000
Net realized gains (losses)   6,836,000 14,976,000 7,327,000
Net unrealized gains (losses)   24,253,000 (17,962,000) 95,539,000
Purchases, issuances and settlements, net   (66,058,000) (1,319,000) (196,564,000)
Fair value of plan assets at Dec. 31   301,359,000 336,328,000 340,633,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   336,328,000 340,633,000 434,331,000
Fair value of plan assets at Dec. 31   301,359,000 336,328,000 340,633,000
Pension Benefits [Member] | Cash Equivalents [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   147,590,000 258,353,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   147,590,000 258,353,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   147,590,000 258,353,000  
Pension Benefits [Member] | Cash Equivalents [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   147,590,000 122,643,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   147,590,000 122,643,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   147,590,000 122,643,000  
Pension Benefits [Member] | Cash Equivalents [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 135,710,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 135,710,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 135,710,000  
Pension Benefits [Member] | Cash Equivalents [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Derivatives [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   8,011,000 8,140,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   8,011,000 8,140,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   8,011,000 8,140,000  
Pension Benefits [Member] | Derivatives [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Derivatives [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   8,011,000 8,140,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   8,011,000 8,140,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   8,011,000 8,140,000  
Pension Benefits [Member] | Derivatives [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Government Securities [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   301,999,000 117,522,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   301,999,000 117,522,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   301,999,000 117,522,000  
Pension Benefits [Member] | Government Securities [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Government Securities [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   301,999,000 117,522,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   301,999,000 117,522,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   301,999,000 117,522,000  
Pension Benefits [Member] | Government Securities [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Corporate Bonds [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   606,001,000 641,807,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   606,001,000 641,807,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   606,001,000 641,807,000  
Pension Benefits [Member] | Corporate Bonds [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Corporate Bonds [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   606,001,000 641,807,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   606,001,000 641,807,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   606,001,000 641,807,000  
Pension Benefits [Member] | Corporate Bonds [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Asset-backed Securities [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   31,368,000 26,986,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   31,368,000 26,986,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   31,368,000 26,986,000  
Pension Benefits [Member] | Asset-backed Securities [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Asset-backed Securities [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Asset-backed Securities [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   31,368,000 26,986,000 47,825,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   26,986,000 47,825,000 77,398,000
Net realized gains (losses)   2,391,000 3,400,000 2,365,000
Net unrealized gains (losses)   (2,504,000) (7,078,000) 45,920,000
Purchases, issuances and settlements, net   4,495,000 (17,161,000) (77,858,000)
Fair value of plan assets at Dec. 31   31,368,000 26,986,000 47,825,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   26,986,000 47,825,000 77,398,000
Fair value of plan assets at Dec. 31   31,368,000 26,986,000 47,825,000
Pension Benefits [Member] | Mortgage-backed Securities [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   73,522,000 113,418,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   73,522,000 113,418,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   73,522,000 113,418,000  
Pension Benefits [Member] | Mortgage-backed Securities [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Mortgage-backed Securities [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Mortgage-backed Securities [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   73,522,000 113,418,000 144,006,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   113,418,000 144,006,000 166,610,000
Net realized gains (losses)   1,103,000 13,719,000 5,531,000
Net unrealized gains (losses)   (5,926,000) (19,095,000) 97,939,000
Purchases, issuances and settlements, net   (35,073,000) (25,212,000) (126,074,000)
Fair value of plan assets at Dec. 31   73,522,000 113,418,000 144,006,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   113,418,000 144,006,000 166,610,000
Fair value of plan assets at Dec. 31   73,522,000 113,418,000 144,006,000
Pension Benefits [Member] | Common Stock [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   68,553,000 117,899,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   68,553,000 117,899,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   68,553,000 117,899,000  
Pension Benefits [Member] | Common Stock [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Common Stock [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Private Equity Investments [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   159,363,000 122,223,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   159,363,000 122,223,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   159,363,000 122,223,000  
Pension Benefits [Member] | Private Equity Investments [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Private Equity Investments [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Private Equity Investments [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   159,363,000 122,223,000 82,098,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   122,223,000 82,098,000 81,034,000
Net realized gains (losses)   3,971,000 (1,008,000) 0
Net unrealized gains (losses)   12,412,000 (24,000) (5,682,000)
Purchases, issuances and settlements, net   20,757,000 41,157,000 6,746,000
Fair value of plan assets at Dec. 31   159,363,000 122,223,000 82,098,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   122,223,000 82,098,000 81,034,000
Fair value of plan assets at Dec. 31   159,363,000 122,223,000 82,098,000
Pension Benefits [Member] | Commingled Funds [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   1,292,569,000 1,152,386,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   1,292,569,000 1,152,386,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   1,292,569,000 1,152,386,000  
Pension Benefits [Member] | Commingled Funds [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Commingled Funds [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   1,292,569,000 1,152,386,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   1,292,569,000 1,152,386,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   1,292,569,000 1,152,386,000  
Pension Benefits [Member] | Commingled Funds [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Real Estate [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   37,106,000 73,701,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   37,106,000 73,701,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   37,106,000 73,701,000  
Pension Benefits [Member] | Real Estate [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Real Estate [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Real Estate [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   37,106,000 73,701,000 66,704,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   73,701,000 66,704,000 109,289,000
Net realized gains (losses)   (629,000) (1,135,000) (569,000)
Net unrealized gains (losses)   20,271,000 8,235,000 (42,638,000)
Purchases, issuances and settlements, net   (56,237,000) (103,000) 622,000
Fair value of plan assets at Dec. 31   37,106,000 73,701,000 66,704,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   73,701,000 66,704,000 109,289,000
Fair value of plan assets at Dec. 31   37,106,000 73,701,000 66,704,000
Pension Benefits [Member] | Securities Lending Collateral Obligation and Other [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   (55,802,000) (91,727,000)  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (55,802,000) (91,727,000)  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (55,802,000) (91,727,000)  
Pension Benefits [Member] | Securities Lending Collateral Obligation and Other [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Pension Benefits [Member] | Securities Lending Collateral Obligation and Other [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   (55,802,000) (91,727,000)  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (55,802,000) (91,727,000)  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (55,802,000) (91,727,000)  
Pension Benefits [Member] | Securities Lending Collateral Obligation and Other [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   426,835,000 432,230,000 384,689,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   432,230,000 384,689,000  
Fair value of plan assets at Dec. 31   426,835,000 432,230,000 384,689,000
Change in Projected Benefit Obligation [Roll Forward]        
Obligation at Jan. 1   794,905,000 728,902,000  
Service cost   4,824,000 4,006,000 4,665,000
Interest cost   42,086,000 42,780,000 50,412,000
Medicare subsidy reimbursements   3,518,000 5,423,000  
ERRP proceeds shared with retirees   4,269,000 0  
Plan amendments   (26,630,000) 0  
Plan participants' contributions   15,690,000 14,315,000  
Actuarial loss   8,823,000 68,126,000  
Benefit payments   (70,638,000) (68,647,000)  
Obligation at Dec. 31   776,847,000 794,905,000 728,902,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   432,230,000 384,689,000  
Actual return on plan assets   535,000 53,430,000  
Plan participants' contributions   15,690,000 14,315,000  
Employer contributions   49,018,000 48,443,000  
Benefit payments   (70,638,000) (68,647,000)  
Fair value of plan assets at Dec. 31   426,835,000 432,230,000 384,689,000
Funded Status of Plans at Dec. 31 [Abstract]        
Funded status   (350,012,000) (362,675,000)  
Current assets   332,000 0  
Current liabilities   (7,594,000) (5,392,000)  
Noncurrent liabilities   (342,750,000) (357,283,000)  
Net postretirement amounts recognized on consolidated balance sheets   (350,012,000) (362,675,000)  
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]        
Net loss   246,846,000 221,335,000  
Prior service cost (credit)   (50,652,000) (28,954,000)  
Transition obligation   15,147,000 29,591,000  
Total   211,341,000 221,972,000  
Amounts Related to the Funded Status of the Plans Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]        
Current regulatory assets   26,139,000 20,225,000  
Noncurrent regulatory assets   176,730,000 197,952,000  
Current regulatory liabilities   (1,866,000) 0  
Noncurrent regulatory liabilities   0 (6,423,000)  
Deferred income taxes   4,207,000 4,159,000  
Net-of-tax accumulated other comprehensive income   6,131,000 6,059,000  
Total   211,341,000 221,972,000  
Measurement date   Dec. 31, 2011 Dec. 31, 2010  
Significant Assumptions Used to Measure Benefit Obligations [Abstract]        
Discount rate for year-end valuation (in hundredths)   5.00% 5.50%  
Mortality table   RP 2000 RP 2000  
Health care costs trend rate - initial (in hundredths)   6.31% 6.50%  
Ultimate health care trend assumption rate (in hundredths)   5.00%    
Period until ultimate health care cost trend rate is reached (in years)   8Y    
Significant Assumptions Used to Measure Costs [Abstract]        
Discount rate (in hundredths)   5.50% 6.00% 6.75%
Expected average long-term rate of return on assets (in hundredths)   7.50% 7.50% 7.50%
Cash Flows [Abstract]        
Total contributions to Xcel Energy's postretirement health care plans during the year   49,000,000 48,400,000  
Expected contribution to postretirement health care plans during 2012   39,100,000    
Components of Net Periodic Benefit Cost (Credit) [Abstract]        
Service cost   4,824,000 4,006,000 4,665,000
Interest cost   42,086,000 42,780,000 50,412,000
Expected return on plan assets   (31,962,000) (28,529,000) (22,775,000)
Amortization of transition obligation   14,444,000 14,444,000 14,444,000
Amortization of prior service cost   (4,932,000) (4,932,000) (2,726,000)
Amortization of net loss   13,294,000 11,643,000 19,329,000
Net periodic benefit cost (credit)   37,754,000 39,412,000 63,349,000
Additional cost recognized due to effects of regulation   3,891,000 3,891,000 3,891,000
Net benefit cost (credit) recognized for financial reporting   41,645,000 43,303,000 67,240,000
Postretirement Health Care Benefits [Abstract]        
Amortization period for unrecognized accumulated postretirement benefit obligation (in years)   20    
Amortization period for Colorado jurisdictional postretirement benefit costs deferred during transition period (in years)   15    
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]        
1-percent increase in APBO   79,710,000    
1-percent decrease in APBO   (65,195,000)    
1-percent increase in service and interest components   5,598,000    
1-percent decrease in service and interest components   (4,456,000)    
Defined Benefit Plan, Gross Projected Benefit Payments [Abstract]        
2012   57,461,000    
2013   57,318,000    
2014   58,396,000    
2015   59,880,000    
2016   61,375,000    
2017-2021   315,139,000    
Expected Medicare Part D Subsidies [Abstract]        
2012   4,523,000    
2013   4,871,000    
2014   5,175,000    
2015   5,471,000    
2016   5,751,000    
2017-2021   32,659,000    
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]        
2012   52,938,000    
2013   52,447,000    
2014   53,221,000    
2015   54,409,000    
2016   55,624,000    
2017-2021   282,480,000    
Multiemployer contributions   336,000 153,000 140,000
Postretirement Health Care Benefits [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   58,388,000 72,573,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   58,388,000 72,573,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   58,388,000 72,573,000  
Postretirement Health Care Benefits [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   332,704,000 337,860,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   332,704,000 337,860,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   332,704,000 337,860,000  
Postretirement Health Care Benefits [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   35,743,000 21,797,000 55,371,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   21,797,000 55,371,000 78,693,000
Net realized gains (losses)   (1,669,000) (1,186,000) 737,000
Net unrealized gains (losses)   1,978,000 17,715,000 3,314,000
Purchases, issuances and settlements, net   13,637,000 (50,103,000) (27,373,000)
Fair value of plan assets at Dec. 31   35,743,000 21,797,000 55,371,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   21,797,000 55,371,000 78,693,000
Fair value of plan assets at Dec. 31   35,743,000 21,797,000 55,371,000
Postretirement Health Care Benefits [Member] | Cash Equivalents [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   58,037,000 148,925,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   58,037,000 148,925,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   58,037,000 148,925,000  
Postretirement Health Care Benefits [Member] | Cash Equivalents [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   58,037,000 72,573,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   58,037,000 72,573,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   58,037,000 72,573,000  
Postretirement Health Care Benefits [Member] | Cash Equivalents [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 76,352,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 76,352,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 76,352,000  
Postretirement Health Care Benefits [Member] | Cash Equivalents [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Derivatives [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   13,178,000 13,632,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   13,178,000 13,632,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   13,178,000 13,632,000  
Postretirement Health Care Benefits [Member] | Derivatives [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Derivatives [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   13,178,000 13,632,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   13,178,000 13,632,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   13,178,000 13,632,000  
Postretirement Health Care Benefits [Member] | Derivatives [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Government Securities [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   65,746,000 3,402,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   65,746,000 3,402,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   65,746,000 3,402,000  
Postretirement Health Care Benefits [Member] | Government Securities [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Government Securities [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   65,746,000 3,402,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   65,746,000 3,402,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   65,746,000 3,402,000  
Postretirement Health Care Benefits [Member] | Government Securities [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Corporate Bonds [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   61,524,000 70,752,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   61,524,000 70,752,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   61,524,000 70,752,000  
Postretirement Health Care Benefits [Member] | Corporate Bonds [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Corporate Bonds [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   61,524,000 70,752,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   61,524,000 70,752,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   61,524,000 70,752,000  
Postretirement Health Care Benefits [Member] | Corporate Bonds [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Asset-backed Securities [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   7,867,000 2,585,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   7,867,000 2,585,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   7,867,000 2,585,000  
Postretirement Health Care Benefits [Member] | Asset-backed Securities [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Asset-backed Securities [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Asset-backed Securities [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   7,867,000 2,585,000 8,293,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   2,585,000 8,293,000 8,705,000
Net realized gains (losses)   (10,000) (259,000) 4,000
Net unrealized gains (losses)   (664,000) 2,073,000 1,025,000
Purchases, issuances and settlements, net   5,956,000 (7,522,000) (1,441,000)
Fair value of plan assets at Dec. 31   7,867,000 2,585,000 8,293,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   2,585,000 8,293,000 8,705,000
Fair value of plan assets at Dec. 31   7,867,000 2,585,000 8,293,000
Postretirement Health Care Benefits [Member] | Mortgage-backed Securities [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   27,253,000 19,212,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   27,253,000 19,212,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   27,253,000 19,212,000  
Postretirement Health Care Benefits [Member] | Mortgage-backed Securities [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Mortgage-backed Securities [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Mortgage-backed Securities [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   27,253,000 19,212,000 47,078,000
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   19,212,000 47,078,000 69,988,000
Net realized gains (losses)   (1,669,000) (927,000) 733,000
Net unrealized gains (losses)   2,623,000 15,642,000 2,289,000
Purchases, issuances and settlements, net   7,087,000 (42,581,000) (25,932,000)
Fair value of plan assets at Dec. 31   27,253,000 19,212,000 47,078,000
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   19,212,000 47,078,000 69,988,000
Fair value of plan assets at Dec. 31   27,253,000 19,212,000 47,078,000
Postretirement Health Care Benefits [Member] | Common Stock [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   351,000    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   351,000    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   351,000    
Postretirement Health Care Benefits [Member] | Common Stock [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   351,000    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   351,000    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   351,000    
Postretirement Health Care Benefits [Member] | Common Stock [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Postretirement Health Care Benefits [Member] | Common Stock [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Postretirement Health Care Benefits [Member] | Private Equity Investments [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   479,000    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   479,000    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   479,000    
Postretirement Health Care Benefits [Member] | Private Equity Investments [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Postretirement Health Care Benefits [Member] | Private Equity Investments [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Postretirement Health Care Benefits [Member] | Private Equity Investments [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   479,000    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   0    
Net realized gains (losses)   12,000    
Net unrealized gains (losses)   53,000    
Purchases, issuances and settlements, net   414,000    
Fair value of plan assets at Dec. 31   479,000    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   0    
Fair value of plan assets at Dec. 31   479,000    
Postretirement Health Care Benefits [Member] | Preferred Stock [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   423,000 507,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   423,000 507,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   423,000 507,000  
Postretirement Health Care Benefits [Member] | Preferred Stock [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Preferred Stock [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   423,000 507,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   423,000 507,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   423,000 507,000  
Postretirement Health Care Benefits [Member] | Preferred Stock [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Commingled Funds [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   202,912,000 102,962,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   202,912,000 102,962,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   202,912,000 102,962,000  
Postretirement Health Care Benefits [Member] | Commingled Funds [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Commingled Funds [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   202,912,000 102,962,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   202,912,000 102,962,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   202,912,000 102,962,000  
Postretirement Health Care Benefits [Member] | Commingled Funds [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Real Estate [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   144,000    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   0    
Net realized gains (losses)   (2,000)    
Net unrealized gains (losses)   (34,000)    
Purchases, issuances and settlements, net   180,000    
Fair value of plan assets at Dec. 31   144,000    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1   0    
Fair value of plan assets at Dec. 31   144,000    
Postretirement Health Care Benefits [Member] | Real Estate [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Postretirement Health Care Benefits [Member] | Real Estate [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0    
Postretirement Health Care Benefits [Member] | Real Estate [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   144,000    
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   144,000    
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   144,000    
Postretirement Health Care Benefits [Member] | Securities Lending Collateral Obligation and Other [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   (11,079,000) 70,253,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (11,079,000) 70,253,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (11,079,000) 70,253,000  
Postretirement Health Care Benefits [Member] | Securities Lending Collateral Obligation and Other [Member] | Level 1 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Postretirement Health Care Benefits [Member] | Securities Lending Collateral Obligation and Other [Member] | Level 2 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   (11,079,000) 70,253,000  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (11,079,000) 70,253,000  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   (11,079,000) 70,253,000  
Postretirement Health Care Benefits [Member] | Securities Lending Collateral Obligation and Other [Member] | Level 3 [Member]
        
Plan Assets Measured at Fair Value for Each of the Fair Value Hierarchy Levels [Abstract]        
Fair value of plan assets   0 0  
Changes in Level 3 Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Dec. 31   0 0  
NSP-Minnesota [Member]
        
Employees Represented by Local Labor Unions Under Collective Bargaining Agreements Receiving Benefits [Abstract]        
Number of bargaining employees receiving benefits under several collective bargaining agreements   2,033    
Number of nuclear operation bargaining employees receiving benefits under collective bargaining-agreements   228    
NSP-Minnesota [Member] | Pension Benefits [Member]
        
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]        
Multiemployer contributions   17,811,000 13,461,000 11,348,000
NSP-Minnesota [Member] | Postretirement Health Care Benefits [Member]
        
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]        
Multiemployer contributions   336,000 153,000 140,000
NSP-Wisconsin [Member]
        
Employees Represented by Local Labor Unions Under Collective Bargaining Agreements Receiving Benefits [Abstract]        
Number of bargaining employees receiving benefits under several collective bargaining agreements   405    
NSP-Wisconsin [Member] | Pension Benefits [Member]
        
Defined Benefit Plan, Net Projected Benefit Payments [Abstract]        
Multiemployer contributions   $ 169,000 $ 170,000 $ 116,000
PSCo [Member]
        
Employees Represented by Local Labor Unions Under Collective Bargaining Agreements Receiving Benefits [Abstract]        
Number of bargaining employees receiving benefits under several collective bargaining agreements   2,122    
SPS [Member]
        
Employees Represented by Local Labor Unions Under Collective Bargaining Agreements Receiving Benefits [Abstract]        
Number of bargaining employees receiving benefits under several collective bargaining agreements   804    
[1] Amounts are recognized in noncurrent liabilities on Xcel Energy's consolidated balance sheet.