XML 77 R63.htm IDEA: XBRL DOCUMENT v3.10.0.1
Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Funded Status of Plans at Dec. 31 [Abstract]        
Noncurrent liabilities   $ (44.5) $ (50.0)  
Cash Flows [Abstract]        
Total contributions to Xcel Energy's postretirement health care plans during the year   0.3 2.0 $ 1.0
Other Postretirement Benefits Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant     0.1  
Plan amendments   0.0 0.0  
Change in Projected Benefit Obligation [Roll Forward]        
Obligation at Jan. 1 $ 12.8 16.4 15.0  
Service cost   0.0 0.0 0.0
Interest cost   0.6 0.6 0.7
Actuarial loss   (3.3) 2.1  
Benefit payments   (0.9) (1.4)  
Obligation at Dec. 31   12.8 16.4 15.0
Change in Fair Value of Plan Assets [Roll Forward]        
Fair value of plan assets at Jan. 1 0.4 1.1 0.5  
Actual return (loss) on plan assets   0.0 0.0  
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant   0.0 0.1  
Employer contributions   0.2 1.9  
Benefit payments   (0.9) (1.4)  
Fair value of plan assets at Dec. 31   0.4 1.1 0.5
Funded Status of Plans at Dec. 31 [Abstract]        
Funded status   (12.4) (15.3)  
Current liabilities   (0.8) (0.3)  
Noncurrent liabilities   (11.6) (15.0)  
Net postretirement amounts recognized on consolidated balance sheets   (12.4) (15.3)  
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]        
Net loss   6.8 10.6  
Prior service (credit) cost   (1.4) (1.8)  
Total   5.4 8.8  
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   0.2 0.1  
Noncurrent regulatory assets   5.2 8.7  
Current regulatory liabilities   0.0 0.0  
Noncurrent regulatory liabilities   0.0 0.0  
Deferred income taxes   0.0 0.0  
Net-of-tax accumulated other comprehensive income   0.0 0.0  
Total   $ 5.4 $ 8.8  
Significant Assumptions Used to Measure Benefit Obligations [Abstract]        
Discount rate for year-end valuation (as a percent)   4.32% 3.62%  
Mortality table   RP-2014 RP-2014  
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65   6.50% 7.00%  
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65   5.30% 5.50%  
Ultimate health care trend assumption rate (as a percent)   4.50% 4.50%  
Period until ultimate trend rate is reached (in years)   4 5  
Components of Net Periodic Benefit Cost (Credit) [Abstract]        
Service cost   $ 0.0 $ 0.0 0.0
Interest cost   0.6 0.6 0.7
Expected return on plan assets   (0.1) 0.0 0.0
Amortization of prior service cost (credit)   (0.4) (0.4) (0.4)
Amortization of net loss   0.6 0.4 0.3
Settlement charge   0.0 0.0 0.0
Net periodic benefit cost   $ 0.7 $ 0.6 $ 0.6
Significant Assumptions Used to Measure Costs [Abstract]        
Discount rate (as a percent)   3.62% 4.13% 4.65%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase   0.00% 0.00% 0.00%
Expected average long-term rate of return on assets (as a percent)   5.30% 5.80% 5.80%
Defined Benefit Plan Credits (Costs) Not Recognized Due To Effects of Regulation   $ 0.0 $ 0.0 $ 0.0
Net benefit cost recognized for financial reporting   0.7 0.6 0.6
Parent Company [Member]        
Cash Flows [Abstract]        
Total contributions to Xcel Energy's postretirement health care plans during the year   $ 11.0 $ 20.0 $ 18.0
Subsequent Event        
Cash Flows [Abstract]        
Expected contribution to postretirement health care plans during 2018 1.0      
Subsequent Event | Parent Company [Member]        
Cash Flows [Abstract]        
Expected contribution to postretirement health care plans during 2018 $ 11.0