v3.25.4
Business Segment Information (Schedule Of Operating Income Derived From Revenues And Expenses By Segment) (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Segment Reporting Information [Line Items]        
Operating Revenues $ 6,642.2 $ 6,642.2 $ 5,455.1 $ 5,505.4
Cost of energy   1,584.4 1,132.2 1,533.3
O&M   1,710.2 1,515.2 1,494.9
Depreciation and amortization   1,167.6 1,043.2 908.2
Total other taxes   344.1 300.0 270.6
Operating Income   1,835.3 1,455.5 1,295.5
Capital Expenditures   4,051.6 3,692.5 2,690.7
Consolidated Assets 35,858.7 35,858.7 31,788.1 31,077.2
Total Reportable Segments        
Segment Reporting Information [Line Items]        
Operating Revenues   6,651.8 5,468.0 5,517.7
Cost of energy   1,584.5 1,132.2 1,533.3
O&M   1,772.6 1,598.9 1,580.0
Depreciation and amortization   1,131.8 999.4 865.5
Total other taxes   328.7 282.9 256.7
Other segment items   1.0 6.1 2.2
Operating Income   1,833.2 1,448.5 1,280.0
Capital Expenditures   3,721.9 3,461.4 2,454.4
Consolidated Assets 34,030.4 34,030.4 30,593.0 27,627.1
Total Reportable Segments | Nonrelated Party        
Segment Reporting Information [Line Items]        
Operating Revenues   6,637.4 5,454.2 5,504.6
Total Reportable Segments | Intersegment revenue        
Segment Reporting Information [Line Items]        
Operating Revenues   14.4 13.8 13.1
Corporate and Other        
Segment Reporting Information [Line Items]        
Operating Revenues   600.1 581.9 504.6
Operating Income   2.1 7.0 15.5
Capital Expenditures   329.7 231.1 236.3
Consolidated Assets 1,828.3 1,828.3 1,195.1 3,450.1
Eliminations        
Segment Reporting Information [Line Items]        
Operating Revenues   (609.7) (594.8) (516.9)
Columbia Operations        
Segment Reporting Information [Line Items]        
Operating Revenues   3,330.0 2,703.2 2,733.9
Columbia Operations | Total Reportable Segments        
Segment Reporting Information [Line Items]        
Operating Revenues   3,343.3 2,716.0 2,746.1
Cost of energy   819.8 514.7 645.0
O&M   923.7 837.5 792.3
Depreciation and amortization   451.2 409.1 371.7
Total other taxes   253.2 218.6 198.8
Other segment items   0.3 7.4 0.0
Operating Income   895.1 728.7 738.3
Capital Expenditures   (1,213.0) (1,209.0) (1,159.6)
Consolidated Assets 15,903.7 15,903.7 14,769.5 13,664.5
Columbia Operations | Total Reportable Segments | Nonrelated Party        
Segment Reporting Information [Line Items]        
Operating Revenues   3,330.0 2,703.2 2,733.9
Columbia Operations | Total Reportable Segments | Intersegment revenue        
Segment Reporting Information [Line Items]        
Operating Revenues   13.3 12.8 12.2
NIPSCO Operations        
Segment Reporting Information [Line Items]        
Operating Revenues 3,307.3      
NIPSCO Operations | Total Reportable Segments        
Segment Reporting Information [Line Items]        
Operating Revenues   3,308.5 2,752.0 2,771.6
Cost of energy   764.7 617.5 888.3
O&M   848.9 761.4 787.7
Depreciation and amortization   680.6 590.3 493.8
Total other taxes   75.5 64.3 57.9
Other segment items   0.7 (1.3) 2.2
Operating Income   938.1 719.8 541.7
Capital Expenditures   (2,508.9) (2,252.4) (1,294.8)
Consolidated Assets $ 18,126.7 18,126.7 15,823.5 13,962.6
NIPSCO Operations | Total Reportable Segments | Nonrelated Party        
Segment Reporting Information [Line Items]        
Operating Revenues   3,307.4 2,751.0 2,770.7
NIPSCO Operations | Total Reportable Segments | Intersegment revenue        
Segment Reporting Information [Line Items]        
Operating Revenues   $ 1.1 $ 1.0 $ 0.9