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Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Funded Status of Plans at Dec. 31 [Abstract]      
Noncurrent liabilities $ (49,889) $ (51,313)  
Postretirement Benefit Plan      
Change in Projected Benefit Obligation [Roll Forward]      
Obligation at Jan. 1 16,768 17,153  
Service cost 29 35 $ 25
Interest cost 653 791 760
Medicare subsidy reimbursements 13 2  
Plan participants' contributions 130 284  
Actuarial (gain) loss (1,645) (38)  
Benefit payments (1,230) (1,459)  
Obligation at Dec. 31 14,718 16,768 17,153
Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets at Jan. 1 512 746  
Actual return (loss) on plan assets (12) (15)  
Plan participants' contributions 130 284  
Employer contributions 1,018 956  
Benefit payments (1,230) (1,459)  
Fair value of plan assets at Dec. 31 418 512 746
Funded Status of Plans at Dec. 31 [Abstract]      
Funded status (14,300) (16,256)  
Current liabilities (1,017) (1,022)  
Noncurrent liabilities (13,283) (15,234)  
Net postretirement amounts recognized on consolidated balance sheets (14,300) (16,256)  
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]      
Net loss 8,402 10,461  
Prior service (credit) cost (2,485) (2,836)  
Total 5,917 7,625  
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]      
Current regulatory assets 99 95  
Noncurrent regulatory assets 5,818 7,530  
Total $ 5,917 $ 7,625  
Significant Assumptions Used to Measure Benefit Obligations [Abstract]      
Measurement date 12/31/2015 12/31/2014  
Discount rate for year-end valuation (as a percent) 4.65% 4.08%  
Mortality table RP 2014 RP 2014  
Health care costs trend rate - initial (as a percent) 6.00% 6.50%  
Ultimate health care trend assumption rate (as a percent) 4.50%    
Period until ultimate trend rate is reached (in years) 3 years    
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]      
One-percent increase in APBO $ 1,420    
One-percent decrease in APBO (1,208)    
One-percent increase in service and interest components 77    
One-percent decrease in service and interest components (65)    
Cash Flows [Abstract]      
Total contributions to Xcel Energy's postretirement health care plans during the year 1,000 $ 1,000 1,500
Expected contribution to postretirement health care plans during 2015 1,400    
Components of Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost 29 35 25
Interest cost 653 791 760
Expected return on plan assets (30) (52) (42)
Amortization of transition obligation 0 0 1
Amortization of prior service cost (credit) (351) (351) (351)
Amortization of net loss 456 666 963
Net periodic benefit cost $ 757 $ 1,089 $ 1,356
Significant Assumptions Used to Measure Costs [Abstract]      
Discount rate (as a percent) 4.08% 4.82% 4.10%
Expected average long-term rate of return on assets (as a percent) 5.80% 7.08% 7.11%
Xcel Energy Inc. | Postretirement Benefit Plan      
Cash Flows [Abstract]      
Total contributions to Xcel Energy's postretirement health care plans during the year $ 18,300 $ 17,100 $ 17,600
Expected contribution to postretirement health care plans during 2015 $ 12,300