v3.25.2
Document And Entity Information - shares
 6 Months Ended
Jun. 30, 2025
Jul. 30, 2025
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 001-16189  
Entity Registrant Name NiSource Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 35-2108964  
Entity Address, Address Line One 801 East 86th Avenue  
Entity Address, City or Town Merrillville,  
Entity Address, State or Province IN  
Entity Address, Postal Zip Code 46410  
City Area Code (877)  
Local Phone Number 647-5990  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   470,855,009
Entity Central Index Key 0001111711  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Common Stock    
Document Information [Line Items]    
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol NI  
Security Exchange Name NYSE