v3.26.1
Fair Value Measurements (Details) - EBP 005 - USD ($)
Dec. 31, 2025
Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments $ 2,314,717,802 $ 1,995,108,955
Mutual funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 142,728,000 349,785,674
Money market fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 69,805,046 77,421,990
Total    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 452,919,891 650,577,082
Total | Mutual funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 142,728,000 349,785,674
Total | NiSource Inc. common stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 237,993,144 221,265,715
Total | Money market government portfolio    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 2,393,701 2,103,703
Total | Money market fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 69,805,046 77,421,990
(Level 1)    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 452,919,891 650,577,082
(Level 1) | Mutual funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 142,728,000 349,785,674
(Level 1) | NiSource Inc. common stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 237,993,144 221,265,715
(Level 1) | Money market government portfolio    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 2,393,701 2,103,703
(Level 1) | Money market fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 69,805,046 77,421,990
(Level 2)    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 2) | Mutual funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 2) | NiSource Inc. common stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 2) | Money market government portfolio    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 2) | Money market fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 3)    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 3) | Mutual funds    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 3) | NiSource Inc. common stock    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 3) | Money market government portfolio    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments 0 0
(Level 3) | Money market fund    
EBP, Investment, Fair Value and NAV [Line Items]    
Total investments $ 0 $ 0