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Share-Based Compensation, Share-Based Compensation Expense (Details) - USD ($)
shares in Thousands, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-Based Compensation Expense [Abstract]      
Granted (in shares) 503 522 496
Compensation cost for share-based awards [1] $ 57 $ 41 $ 45
Tax benefit recognized in income 22 16 $ 18
Unrecognized compensation cost related to nonvested share-based compensation awards $ 44 $ 29  
Weighted-average period for recognition of unrecognized compensation cost related to nonvested share-based compensation awards (in years) 1 year 8 months    
Award Vesting Period (in years) 3 years    
Xcel Energy Inc. 2015 Omnibus Incentive Plan [Member]      
Share-Based Compensation Expense [Abstract]      
Number of shares of common stock approved for issuance (in shares) 7,000    
Xcel Energy Inc. Long-Term Incentive Plan [Member]      
Share-Based Compensation Expense [Abstract]      
Number of shares of common stock approved for issuance (in shares) 8,300    
Xcel Energy Inc. Executive Annual Incentive Award Plan [Member]      
Share-Based Compensation Expense [Abstract]      
Number of shares of common stock approved for issuance (in shares) 1,200    
Service-based awards [Member]      
Share-Based Compensation Expense [Abstract]      
Granted (in shares) 300 300 300
[1] Compensation costs for share-based payment arrangements are included in O&M expense in the consolidated statements of income.