Regulatory Matters	9 Months Ended
Regulatory Matters	Sep. 30, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]
Regulatory Matters	NIPSCO change in accounting estimate As part of the NIPSCO Gas Settlement and Stipulation Agreement filed on March 2, 2022, NIPSCO Gas agreed to change the depreciation methodology for its calculation of depreciation rates, which reduces depreciation expense and subsequent revenues and cash flows. An order was received on July 27, 2022 approving the settlement and rates were effective as of September 1, 2022. As part of the NIPSCO Electric base rate case and the Stipulation and Settlement Agreement filed on March 10, 2023, NIPSCO Electric agreed to change the depreciation methodology for its calculation of depreciation rates, which will reduce depreciation expense and subsequent revenues and cash flows. An order was received on August 2, 2023 approving the settlement, and rates were effective as of August 4, 2023. On October 11, 2023, the IURC issued an order clarifying how the rate increase should have been implemented, holding that the new rates should have only applied to electric usage on or after August 4, 2023, and not for electric usage prior to that date for bills yet to be rendered. NIPSCO was ordered to make a filing reflecting the calculation of the refund to customers by November 10, 2023. The refund amount was reserved for an estimated $12.4 million plus accrued interest. Columbia of Ohio regulatory filing update Columbia of Ohio's base rate case was filed on June 30, 2021, requesting a net rate increase of approximately 21.3% or $221.4 million increase in revenue per year. The case was filed in conjunction with applications for an alternative rate plan, approval of certain deferral authority, and updates to certain riders. On October 31, 2022, Columbia of Ohio filed a joint stipulation and recommendation with certain parties to settle the base rate case. On January 26, 2023, the PUCO modified and approved the joint stipulation and recommendation, and Columbia of Ohio placed rates into effect on March 1, 2023. Applications for Rehearing were filed by the three parties who opposed certain rate design and energy efficiency assistance components of the joint stipulation and recommendation, which was granted for further consideration by the PUCO on March 22, 2023. Regulatory deferral related to renewable energy investments In accordance with the accounting principles of ASC 980, we recognize a regulatory liability or asset for amounts representing the timing difference between the profit earned from the JVs and the amount included in regulated rates to recover our approved investments in consolidated JVs. The amounts recorded in income will ultimately reflect the amount allowed in regulated rates to recover our investments over the useful life of the projects. The offset to the regulatory liability or asset associated with our renewable investments included in regulated rates is recorded in "Depreciation and amortization" on the Condensed Statements of Consolidated Income (unaudited). NiSource recorded a decrease to depreciation expense of $19.0 million and $9.7 million for the three and nine months ended September 30, 2023. We recorded a decrease to depreciation expense of $2.2 million and an increase to depreciation expense of $4.5 million respectively, for the three and nine months ended September 30, 2022. Following the implementation of the electric base rate case, we began recognizing amounts to recover our investments of projects that have been placed in service. Refer to Note 11, "Variable Interest Entities," for additional information.