v3.25.2
Cover Page - shares
6 Months Ended
Jun. 30, 2025
Jul. 31, 2025
Cover [Abstract]    
Entity Registrant Name NORTHERN STATES POWER CO  
Entity Central Index Key 0001123852  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Document Period End Date Jun. 30, 2025  
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Entity File Number 001-31387  
Entity Incorporation, State or Country Code MN  
Entity Tax Identification Number 41-1967505  
Entity Address, Address Line One 414 Nicollet Mall,  
Entity Address, City or Town Minneapolis,  
Entity Address, State or Province MN  
Entity Address, Postal Zip Code 55401  
City Area Code (612)  
Local Phone Number 330-5500  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   1,000,000