v3.26.1
SEGMENT INFORMATION (Details)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Jun. 30, 2026
USD ($)
numberOfSegments
Jun. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Segment information                
Number of reportable segments | numberOfSegments         6      
Operating revenues $ 2,062.1   $ 2,009.5   $ 5,496.3 $ 5,159.0    
Fuel and purchased power costs 383.7   391.8   833.5 782.1    
Cost of natural gas sold 171.9   178.7   1,113.1 954.1    
Other operation and maintenance 617.1   596.2   1,225.8 1,204.2    
Depreciation and amortization 384.9   368.9   764.7 728.8    
Property and revenue taxes 71.7   69.0   146.4 147.4    
Equity in earnings of transmission affiliates 62.6   51.9   122.1 105.5    
Other income, net 61.5   26.5   109.7 44.6    
Interest expense 228.9   220.8   457.4 443.8    
Income tax expense (benefit) 27.0   19.5   80.1 80.2    
Preferred stock dividends of subsidiary 0.3   0.3   0.6 0.6    
Net (income) loss attributed to noncontrolling interests (1.5) $ (1.4) 2.7 $ (1.0) (2.9) 1.7    
Net income (loss) attributed to common shareholders 299.2   245.4   1,103.6 969.6    
Capital expenditures and asset acquisitions 1,265.0   829.4   2,082.9 1,936.6    
Equity method investments 2,497.8   2,284.6   2,497.8 2,284.6    
Total assets 52,750.4   48,524.3   52,750.4 48,524.3 $ 51,518.3  
External revenues                
Segment information                
Operating revenues 2,062.1   2,009.5   5,496.3 5,159.0    
Intersegment revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Utility operations                
Segment information                
Fuel and purchased power costs 383.7   391.8   833.5 782.1    
Cost of natural gas sold 181.1   187.9   1,131.0 972.2    
Other operation and maintenance 590.9   552.3   1,184.8 1,143.0    
Depreciation and amortization 347.6   327.3   689.3 647.5    
Property and revenue taxes 66.5   64.1   135.8 137.0    
Equity in earnings of transmission affiliates 0.0   0.0   0.0 0.0    
Other income, net 54.5   22.2   99.7 42.0    
Interest expense 186.5   184.7   376.5 374.0    
Income tax expense (benefit) 37.0   45.4   198.0 211.4    
Preferred stock dividends of subsidiary 0.3   0.3   0.6 0.6    
Net (income) loss attributed to noncontrolling interests 0.0   0.0   0.0 0.0    
Net income (loss) attributed to common shareholders 228.9   208.5   863.5 789.6    
Capital expenditures and asset acquisitions 1,240.9   808.3   2,025.3 1,496.8    
Equity method investments 19.1   16.8   19.1 16.8    
Total assets 44,982.1   40,929.2   44,982.1 40,929.2    
Utility operations | External revenues                
Segment information                
Operating revenues 1,968.0   1,940.1   5,313.3 5,015.4    
Utility operations | Intersegment revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Reconciling eliminations                
Segment information                
Fuel and purchased power costs 0.0   0.0   0.0 0.0    
Cost of natural gas sold (10.0)   (10.5)   (23.1) (23.9)    
Other operation and maintenance (3.9)   (3.9)   (5.5) (5.5)    
Depreciation and amortization (29.1)   (24.8)   (56.9) (48.7)    
Property and revenue taxes 0.0   0.0   0.0 0.0    
Equity in earnings of transmission affiliates 0.0   0.0   0.0 0.0    
Other income, net (9.0)   (8.0)   (16.8) (15.4)    
Interest expense (87.5)   (88.8)   (174.6) (177.4)    
Income tax expense (benefit) 0.0   0.0   0.0 0.0    
Preferred stock dividends of subsidiary 0.0   0.0   0.0 0.0    
Net (income) loss attributed to noncontrolling interests 0.0   0.0   0.0 0.0    
Net income (loss) attributed to common shareholders 0.0   0.0   0.0 0.0    
Capital expenditures and asset acquisitions 0.0   0.0   0.0 0.0    
Equity method investments 0.0   0.0   0.0 0.0    
Total assets (3,660.7)   (3,652.8)   (3,660.7) (3,652.8)    
Reconciling eliminations | WE                
Segment information                
Total assets 2,573.2   2,629.4   2,573.2 2,629.4    
Reconciling eliminations | External revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Reconciling eliminations | Intersegment revenues                
Segment information                
Operating revenues $ (121.5)   (120.0)   $ (243.3) (240.1)    
ATC                
Segment information                
Ownership interest (as a percent) 60.00%       60.00%      
Equity in earnings of transmission affiliates $ 62.2   50.3   $ 121.4 100.3    
Equity method investments $ 2,398.1 2,346.7 2,177.5 2,121.6 $ 2,398.1 2,177.5 2,256.9 $ 2,085.1
ATC Holdco                
Segment information                
Ownership interest (as a percent) 75.00%       75.00%      
Equity in earnings of transmission affiliates $ 0.4   1.6   $ 0.7 5.2    
Equity method investments 22.6 $ 22.8 22.6 $ 27.4 22.6 22.6 $ 23.5 $ 23.8
Wisconsin | Operating Segments                
Segment information                
Operating revenues 1,621.5   1,587.2   3,959.8 3,647.1    
Wisconsin | Operating Segments | Utility operations                
Segment information                
Fuel and purchased power costs 383.7   391.8   833.5 782.1    
Cost of natural gas sold 114.4   128.4   637.4 506.9    
Other operation and maintenance 459.9   416.0   910.1 831.1    
Depreciation and amortization 268.1   250.2   530.8 493.8    
Property and revenue taxes 48.5   44.5   99.8 90.5    
Equity in earnings of transmission affiliates 0.0   0.0   0.0 0.0    
Other income, net 52.2   19.8   95.3 37.4    
Interest expense 161.8   157.9   324.1 319.7    
Income tax expense (benefit) 28.8   35.5   102.5 117.5    
Preferred stock dividends of subsidiary 0.3   0.3   0.6 0.6    
Net (income) loss attributed to noncontrolling interests 0.0   0.0   0.0 0.0    
Net income (loss) attributed to common shareholders 208.2   182.4   616.3 542.3    
Capital expenditures and asset acquisitions 1,115.8   699.5   1,832.1 1,316.4    
Equity method investments 19.1   16.8   19.1 16.8    
Total assets 35,352.5   31,314.9   35,352.5 31,314.9    
Wisconsin | Operating Segments | Utility operations | External revenues                
Segment information                
Operating revenues 1,621.5   1,587.2   3,959.8 3,647.1    
Wisconsin | Operating Segments | Utility operations | Intersegment revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Illinois | Operating Segments                
Segment information                
Operating revenues 262.2   270.6   1,011.9 1,058.9    
Illinois | Operating Segments | Utility operations                
Segment information                
Fuel and purchased power costs 0.0   0.0   0.0 0.0    
Cost of natural gas sold 32.5   29.5   307.7 317.7    
Other operation and maintenance 106.9   112.4   221.1 259.3    
Depreciation and amortization 66.4   64.8   132.3 129.2    
Property and revenue taxes 11.3   12.8   22.3 33.2    
Equity in earnings of transmission affiliates 0.0   0.0   0.0 0.0    
Other income, net 2.0   2.3   4.1 4.4    
Interest expense 19.8   22.1   42.2 45.3    
Income tax expense (benefit) 7.8   8.7   82.0 77.9    
Preferred stock dividends of subsidiary 0.0   0.0   0.0 0.0    
Net (income) loss attributed to noncontrolling interests 0.0   0.0   0.0 0.0    
Net income (loss) attributed to common shareholders 19.5   22.6   208.4 200.7    
Capital expenditures and asset acquisitions 92.6   71.6   148.5 125.4    
Equity method investments 0.0   0.0   0.0 0.0    
Total assets 7,945.2   7,989.9   7,945.2 7,989.9    
Illinois | Operating Segments | Utility operations | External revenues                
Segment information                
Operating revenues 262.2   270.6   1,011.9 1,058.9    
Illinois | Operating Segments | Utility operations | Intersegment revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Other States | Operating Segments                
Segment information                
Operating revenues 84.3   82.3   341.6 309.4    
Other States | Operating Segments | Utility operations                
Segment information                
Fuel and purchased power costs 0.0   0.0   0.0 0.0    
Cost of natural gas sold 34.2   30.0   185.9 147.6    
Other operation and maintenance 24.1   23.9   53.6 52.6    
Depreciation and amortization 13.1   12.3   26.2 24.5    
Property and revenue taxes 6.7   6.8   13.7 13.3    
Equity in earnings of transmission affiliates 0.0   0.0   0.0 0.0    
Other income, net 0.3   0.1   0.3 0.2    
Interest expense 4.9   4.7   10.2 9.0    
Income tax expense (benefit) 0.4   1.2   13.5 16.0    
Preferred stock dividends of subsidiary 0.0   0.0   0.0 0.0    
Net (income) loss attributed to noncontrolling interests 0.0   0.0   0.0 0.0    
Net income (loss) attributed to common shareholders 1.2   3.5   38.8 46.6    
Capital expenditures and asset acquisitions 32.5   37.2   44.7 55.0    
Equity method investments 0.0   0.0   0.0 0.0    
Total assets 1,684.4   1,624.4   1,684.4 1,624.4    
Other States | Operating Segments | Utility operations | External revenues                
Segment information                
Operating revenues 84.3   82.3   341.6 309.4    
Other States | Operating Segments | Utility operations | Intersegment revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Electric Transmission | Operating Segments                
Segment information                
Fuel and purchased power costs 0.0   0.0   0.0 0.0    
Cost of natural gas sold 0.0   0.0   0.0 0.0    
Other operation and maintenance 0.0   0.0   0.0 0.0    
Depreciation and amortization 0.0   0.0   0.0 0.0    
Property and revenue taxes 0.0   0.0   0.0 0.0    
Equity in earnings of transmission affiliates 62.6   51.9   122.1 105.5    
Other income, net 0.0   0.0   0.0 0.0    
Interest expense 4.0   4.9   7.9 9.7    
Income tax expense (benefit) 14.4   11.4   28.1 23.3    
Preferred stock dividends of subsidiary 0.0   0.0   0.0 0.0    
Net (income) loss attributed to noncontrolling interests 0.0   0.0   0.0 0.0    
Net income (loss) attributed to common shareholders 44.2   35.6   86.1 72.5    
Capital expenditures and asset acquisitions 0.0   0.0   0.0 0.0    
Equity method investments 2,420.7   2,200.1   2,420.7 2,200.1    
Total assets 2,423.9   2,201.0   2,423.9 2,201.0    
Electric Transmission | Operating Segments | External revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Electric Transmission | Operating Segments | Intersegment revenues                
Segment information                
Operating revenues $ 0.0   0.0   $ 0.0 0.0    
Electric Transmission | ATC                
Segment information                
Ownership interest (as a percent) 60.00%       60.00%      
Electric Transmission | ATC Holdco                
Segment information                
Ownership interest (as a percent) 75.00%       75.00%      
Non-Utility Energy Infrastructure                
Segment information                
Natural gas storage needs provided to Wisconsin utilities         33.00%      
Non-Utility Energy Infrastructure | Operating Segments                
Segment information                
Operating revenues $ 215.6   189.4   $ 426.3 383.7    
Fuel and purchased power costs 0.0   0.0   0.0 0.0    
Cost of natural gas sold 0.8   1.3   5.2 5.8    
Other operation and maintenance 28.1   50.9   48.6 73.0    
Depreciation and amortization 60.7   60.8   121.4 119.0    
Property and revenue taxes 5.1   4.9   10.5 10.3    
Equity in earnings of transmission affiliates 0.0   0.0   0.0 0.0    
Other income, net 0.7   0.7   1.2 1.4    
Interest expense 30.9   31.5   60.6 62.1    
Income tax expense (benefit) (29.5)   (38.9)   (61.0) (74.5)    
Preferred stock dividends of subsidiary 0.0   0.0   0.0 0.0    
Net (income) loss attributed to noncontrolling interests (1.5)   2.7   (2.9) 1.7    
Net income (loss) attributed to common shareholders 118.7   82.3   239.3 191.1    
Capital expenditures and asset acquisitions 19.6   17.5   46.6 432.1    
Equity method investments 0.0   0.0   0.0 0.0    
Total assets 7,714.8   7,812.7   7,714.8 7,812.7    
Non-Utility Energy Infrastructure | Operating Segments | External revenues                
Segment information                
Operating revenues 94.1   69.4   183.0 143.6    
Non-Utility Energy Infrastructure | Operating Segments | Intersegment revenues                
Segment information                
Operating revenues 121.5   120.0   243.3 240.1    
Corporate and Other | Operating Segments                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Fuel and purchased power costs 0.0   0.0   0.0 0.0    
Cost of natural gas sold 0.0   0.0   0.0 0.0    
Other operation and maintenance 2.0   (3.1)   (2.1) (6.3)    
Depreciation and amortization 5.7   5.6   10.9 11.0    
Property and revenue taxes 0.1   0.0   0.1 0.1    
Equity in earnings of transmission affiliates 0.0   0.0   0.0 0.0    
Other income, net 15.3   11.6   25.6 16.6    
Interest expense 95.0   88.5   187.0 175.4    
Income tax expense (benefit) 5.1   1.6   (85.0) (80.0)    
Preferred stock dividends of subsidiary 0.0   0.0   0.0 0.0    
Net (income) loss attributed to noncontrolling interests 0.0   0.0   0.0 0.0    
Net income (loss) attributed to common shareholders (92.6)   (81.0)   (85.3) (83.6)    
Capital expenditures and asset acquisitions 4.5   3.6   11.0 7.7    
Equity method investments 58.0   67.7   58.0 67.7    
Total assets 1,290.3   1,234.2   1,290.3 1,234.2    
Corporate and Other | Operating Segments | External revenues                
Segment information                
Operating revenues 0.0   0.0   0.0 0.0    
Corporate and Other | Operating Segments | Intersegment revenues                
Segment information                
Operating revenues $ 0.0   $ 0.0   $ 0.0 $ 0.0