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Cover - shares
 9 Months Ended
Sep. 30, 2025
Oct. 30, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2025  
Document Transition Report false  
Entity File Number 0-422  
Registrant Name MIDDLESEX WATER COMPANY  
Entity Incorporation, State or Country Code NJ  
Entity Tax Identification Number 22-1114430  
Entity Address, Address Line One 485C Route One South  
Entity Address, City or Town Iselin  
Entity Address, State or Province NJ  
Entity Address, Postal Zip Code 08830  
City Area Code (732)  
Local Phone Number 634-1500  
Title of 12(b) Security Common Stock  
Trading Symbol MSEX  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   18,337,819
Central Index Key 0000066004  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Document Fiscal Year Focus 2025  
Current Fiscal Year End Date --12-31