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Benefit Plans and Other Postretirement Benefits, Pension Benefits (Details) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Pension Plans [Member]
     
Pension Benefits [Abstract]      
Total benefit obligation $ 179,995,000 $ 159,766,000 $ 154,147,000
Minimum number of years historical achieved weighted average annual returns are used to determine overall expected return on asset portfolio (in years) 20 years    
Expected average long-term rate of return on assets (in hundredths) 7.50% 8.00% 8.00%
Expected average long-term rate of return on assets for next fiscal year (in hundredths) 7.25%    
Target Pension Asset Allocations [Abstract]      
Domestic and international equity securities (in hundredths) 29.00% 31.00%  
Long-duration fixed income securities (in hundredths) 30.00% 26.00%  
Short-to-intermediate fixed income securities (in hundredths) 12.00% 14.00%  
Alternative investments (in hundredths) 27.00% 26.00%  
Cash (in hundredths) 2.00% 3.00%  
Total (in hundredths) 100.00% 100.00%  
Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan [Member]
     
Pension Benefits [Abstract]      
Total benefit obligation 600,000 600,000  
Xcel Energy Inc. [Member] | Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan [Member]
     
Pension Benefits [Abstract]      
Total benefit obligation 39,400,000 54,800,000  
Net benefit cost recognized for financial reporting $ 15,600,000 $ 5,700,000