| Document and Entity Information | Sep. 29, 2020 |
| Document And Entity Information [Line Items] | |
| Entity Central Index Key | 0001111711 |
| Amendment Flag | false |
| Document Type | 8-K |
| Document Period End Date | Sep. 29, 2020 |
| Entity Registrant Name | NiSource Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-16189 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock | |
| Document And Entity Information [Line Items] | |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | NI |
| Security Exchange Name | NYSE |
| Preferred Stock | |
| Document And Entity Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares, each representing a 1/1,000th ownership interest in a share of 6.50% Series B |
| Trading Symbol | NI PR B |
| Security Exchange Name | NYSE |
