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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, 2016
Dec. 31, 2015
Dec. 31, 2014
Funded Status of Plans at Dec. 31 [Abstract]      
Noncurrent liabilities $ (55,164) $ (49,889)  
Postretirement Benefit Plan      
Change in Projected Benefit Obligation [Roll Forward]      
Obligation at Jan. 1 14,718 16,768  
Service cost 24 29 $ 35
Interest cost 651 653 791
Medicare subsidy reimbursements 7 13  
Plan participants' contributions 87 130  
Actuarial (gain) loss 775 (1,645)  
Benefit payments (1,289) (1,230)  
Obligation at Dec. 31 14,973 14,718 16,768
Change in Fair Value of Plan Assets [Roll Forward]      
Fair value of plan assets at Jan. 1 418 512  
Actual return (loss) on plan assets (12) (12)  
Plan participants' contributions 87 130  
Employer contributions 1,339 1,018  
Benefit payments (1,289) (1,230)  
Fair value of plan assets at Dec. 31 543 418 512
Funded Status of Plans at Dec. 31 [Abstract]      
Funded status (14,430) (14,300)  
Current liabilities (822) (1,017)  
Noncurrent liabilities (13,608) (13,283)  
Net postretirement amounts recognized on consolidated balance sheets (14,430) (14,300)  
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]      
Net loss 8,883 8,402  
Prior service (credit) cost (2,134) (2,485)  
Total 6,749 5,917  
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 0 99  
Noncurrent regulatory assets 6,749 5,818  
Total $ 6,749 $ 5,917  
Significant Assumptions Used to Measure Benefit Obligations [Abstract]      
Discount rate for year-end valuation (as a percent) 4.13% 4.65%  
Mortality table RP 2014 RP 2014  
Health care costs trend rate - initial (as a percent) 5.50% 6.00%  
Ultimate health care trend assumption rate (as a percent) 4.50%    
Period until ultimate trend rate is reached (in years) 2 years    
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]      
One-percent increase in APBO $ 1,423    
One-percent decrease in APBO (1,212)    
One-percent increase in service and interest components 71    
One-percent decrease in service and interest components (60)    
Cash Flows [Abstract]      
Total contributions to Xcel Energy's postretirement health care plans during the year 1,300 $ 1,000 1,000
Expected contribution to postretirement health care plans during 2017 1,400    
Components of Net Periodic Benefit Cost (Credit) [Abstract]      
Service cost 24 29 35
Interest cost 651 653 791
Expected return on plan assets (24) (30) (52)
Amortization of prior service cost (credit) (351) (351) (351)
Amortization of net loss 330 456 666
Net periodic benefit cost $ 630 $ 757 $ 1,089
Significant Assumptions Used to Measure Costs [Abstract]      
Discount rate (as a percent) 4.65% 4.08% 4.82%
Expected average long-term rate of return on assets (as a percent) 5.80% 5.80% 7.08%
Xcel Energy Inc. | Postretirement Benefit Plan      
Cash Flows [Abstract]      
Total contributions to Xcel Energy's postretirement health care plans during the year $ 17,900 $ 18,300 $ 17,100
Expected contribution to postretirement health care plans during 2017 $ 11,800