v3.26.3
SEGMENT INFORMATION (Details)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Sep. 30, 2026
USD ($)
numberOfSegments
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Segment information                    
Number of reportable segments | numberOfSegments             6      
Operating revenues $ 2,290.6     $ 2,104.0     $ 7,786.9 $ 7,263.0    
Fuel and purchased power costs 559.1     502.4     1,392.6 1,284.5    
Cost of natural gas sold 92.1     105.7     1,205.2 1,059.8    
Other operation and maintenance 614.4     605.1     1,840.2 1,809.3    
Depreciation and amortization 389.0     373.4     1,153.7 1,102.2    
Property and revenue taxes 72.3     67.8     218.7 215.2    
Equity in earnings of transmission affiliates 65.8     54.8     187.9 160.3    
Other income, net 49.5     23.8     159.2 68.4    
Interest expense 241.7     223.6     699.1 667.4    
Income tax expense (benefit) 47.0     34.4     127.1 114.6    
Preferred stock dividends of subsidiary 0.3     0.3     0.9 0.9    
Net (income) loss attributed to noncontrolling interests (0.7) $ (1.5) $ (1.4) 1.4 $ 2.7 $ (1.0) (3.6) 3.1    
Net income (loss) attributed to common shareholders 389.3     271.3     1,492.9 1,240.9    
Capital expenditures, including AFUDC-Debt and asset acquisitions 1,198.6     1,574.5     3,321.7 3,526.1    
Equity method investments 2,573.6     2,341.4     2,573.6 2,341.4    
Total assets 53,897.5     49,808.9     53,897.5 49,808.9 $ 51,518.3  
External revenues                    
Segment information                    
Operating revenues 2,290.6     2,104.0     7,786.9 7,263.0    
Intersegment revenues                    
Segment information                    
Operating revenues 0.0     0.0     0.0 0.0    
Utility operations                    
Segment information                    
Fuel and purchased power costs 559.1     502.4     1,392.6 1,284.5    
Cost of natural gas sold 101.0     114.7     1,232.0 1,086.9    
Other operation and maintenance 593.2     575.3     1,778.0 1,718.3    
Depreciation and amortization 352.4     333.2     1,041.7 980.7    
Property and revenue taxes 67.0     62.5     202.8 199.5    
Equity in earnings of transmission affiliates 0.0     0.0     0.0 0.0    
Other income, net 46.5     27.2     146.2 69.2    
Interest expense 200.9     185.7     577.4 559.7    
Income tax expense (benefit) 49.7     39.3     247.7 250.7    
Preferred stock dividends of subsidiary 0.3     0.3     0.9 0.9    
Net (income) loss attributed to noncontrolling interests 0.0     0.0     0.0 0.0    
Net income (loss) attributed to common shareholders 331.7     241.9     1,195.2 1,031.5    
Capital expenditures, including AFUDC-Debt and asset acquisitions 1,171.8     1,509.3     3,237.2 3,021.0    
Equity method investments 19.7     17.3     19.7 17.3    
Total assets 46,084.1     42,168.3     46,084.1 42,168.3    
Utility operations | External revenues                    
Segment information                    
Operating revenues 2,208.8     2,028.1     7,522.1 7,043.5    
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 (9.7)     (9.8)     (32.8) (33.7)    
Other operation and maintenance (1.6)     (1.6)     (7.1) (7.1)    
Depreciation and amortization (29.4)     (25.6)     (86.3) (74.3)    
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)     (7.9)     (25.8) (23.3)    
Interest expense (87.4)     (88.3)     (262.0) (265.7)    
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, including AFUDC-Debt and asset acquisitions 0.0     0.0     0.0 0.0    
Equity method investments 0.0     0.0     0.0 0.0    
Total assets (3,643.5)     (3,637.5)     (3,643.5) (3,637.5)    
Reconciling Eliminations | WE                    
Segment information                    
Total assets 2,552.4     2,613.4     2,552.4 2,613.4    
Reconciling Eliminations | External revenues                    
Segment information                    
Operating revenues 0.0     0.0     0.0 0.0    
Reconciling Eliminations | Intersegment revenues                    
Segment information                    
Operating revenues $ (119.1)     (117.4)     $ (362.4) (357.5)    
ATC                    
Segment information                    
Ownership interest (as a percent) 60.00%           60.00%      
Equity in earnings of transmission affiliates $ 65.5     54.2     $ 186.9 154.5    
Equity method investments $ 2,474.1 2,398.1   2,245.6 2,177.5   $ 2,474.1 2,245.6 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 $ 0.3     0.6     $ 1.0 5.8    
Equity method investments 22.9 $ 22.6   23.2 $ 22.6   22.9 23.2 $ 23.5 $ 23.8
Wisconsin | Operating Segments                    
Segment information                    
Operating revenues 1,964.7     1,791.6     5,924.5 5,438.7    
Wisconsin | Operating Segments | Utility operations                    
Segment information                    
Fuel and purchased power costs 559.1     502.4     1,392.6 1,284.5    
Cost of natural gas sold 50.3     75.8     687.7 582.7    
Other operation and maintenance 479.3     443.7     1,389.4 1,274.8    
Depreciation and amortization 271.8     255.7     802.6 749.5    
Property and revenue taxes 49.0     44.5     148.8 135.0    
Equity in earnings of transmission affiliates 0.0     0.0     0.0 0.0    
Other income, net 43.6     25.0     138.9 62.4    
Interest expense 175.0     158.9     499.1 478.6    
Income tax expense (benefit) 61.8     54.0     164.3 171.5    
Preferred stock dividends of subsidiary 0.3     0.3     0.9 0.9    
Net (income) loss attributed to noncontrolling interests 0.0     0.0     0.0 0.0    
Net income (loss) attributed to common shareholders 361.7     281.3     978.0 823.6    
Capital expenditures, including AFUDC-Debt and asset acquisitions 1,011.1     1,385.7     2,883.2 2,716.8    
Equity method investments 19.7     17.3     19.7 17.3    
Total assets 36,318.6     32,467.2     36,318.6 32,467.2    
Wisconsin | Operating Segments | Utility operations | External revenues                    
Segment information                    
Operating revenues 1,964.7     1,791.6     5,924.5 5,438.7    
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 183.2     183.5     1,195.1 1,242.4    
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 27.4     21.4     335.1 339.1    
Other operation and maintenance 89.2     108.0     310.3 367.3    
Depreciation and amortization 67.1     65.0     199.4 194.2    
Property and revenue taxes 11.2     11.4     33.5 44.6    
Equity in earnings of transmission affiliates 0.0     0.0     0.0 0.0    
Other income, net 2.6     2.1     6.7 6.5    
Interest expense 21.1     21.8     63.3 67.1    
Income tax expense (benefit) (9.0)     (11.5)     73.0 66.4    
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 (21.2)     (30.5)     187.2 170.2    
Capital expenditures, including AFUDC-Debt and asset acquisitions 123.4     93.9     271.9 219.3    
Equity method investments 0.0     0.0     0.0 0.0    
Total assets 8,047.2     8,049.4     8,047.2 8,049.4    
Illinois | Operating Segments | Utility operations | External revenues                    
Segment information                    
Operating revenues 183.2     183.5     1,195.1 1,242.4    
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 60.9     53.0     402.5 362.4    
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 23.3     17.5     209.2 165.1    
Other operation and maintenance 24.7     23.6     78.3 76.2    
Depreciation and amortization 13.5     12.5     39.7 37.0    
Property and revenue taxes 6.8     6.6     20.5 19.9    
Equity in earnings of transmission affiliates 0.0     0.0     0.0 0.0    
Other income, net 0.3     0.1     0.6 0.3    
Interest expense 4.8     5.0     15.0 14.0    
Income tax expense (benefit) (3.1)     (3.2)     10.4 12.8    
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 (8.8)     (8.9)     30.0 37.7    
Capital expenditures, including AFUDC-Debt and asset acquisitions 37.3     29.7     82.1 84.9    
Equity method investments 0.0     0.0     0.0 0.0    
Total assets 1,718.3     1,651.7     1,718.3 1,651.7    
Other States | Operating Segments | Utility operations | External revenues                    
Segment information                    
Operating revenues 60.9     53.0     402.5 362.4    
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 65.8     54.8     187.9 160.3    
Other income, net 0.0     0.0     0.0 0.0    
Interest expense 3.9     4.8     11.8 14.5    
Income tax expense (benefit) 15.6     12.7     43.7 36.0    
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 46.3     37.3     132.4 109.8    
Capital expenditures, including AFUDC-Debt and asset acquisitions 0.0     0.0     0.0 0.0    
Equity method investments 2,497.0     2,268.8     2,497.0 2,268.8    
Total assets 2,497.0     2,268.8     2,497.0 2,268.8    
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 $ 200.9     193.3     $ 627.2 577.0    
Fuel and purchased power costs 0.0     0.0     0.0 0.0    
Cost of natural gas sold 0.8     0.8     6.0 6.6    
Other operation and maintenance 30.9     34.6     79.5 107.6    
Depreciation and amortization 60.4     60.6     181.8 179.6    
Property and revenue taxes 5.3     5.3     15.8 15.6    
Equity in earnings of transmission affiliates 0.0     0.0     0.0 0.0    
Other income, net 0.7     0.8     1.9 2.2    
Interest expense 30.0     30.5     90.6 92.6    
Income tax expense (benefit) (19.3)     (24.2)     (80.3) (98.7)    
Preferred stock dividends of subsidiary 0.0     0.0     0.0 0.0    
Net (income) loss attributed to noncontrolling interests (0.7)     1.4     (3.6) 3.1    
Net income (loss) attributed to common shareholders 92.8     87.9     332.1 279.0    
Capital expenditures, including AFUDC-Debt and asset acquisitions 19.2     58.3     65.8 490.4    
Equity method investments 0.0     0.0     0.0 0.0    
Total assets 7,661.1     7,809.9     7,661.1 7,809.9    
Non-Utility Energy Infrastructure | Operating Segments | External revenues                    
Segment information                    
Operating revenues 81.8     75.9     264.8 219.5    
Non-Utility Energy Infrastructure | Operating Segments | Intersegment revenues                    
Segment information                    
Operating revenues 119.1     117.4     362.4 357.5    
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 (8.1)     (3.2)     (10.2) (9.5)    
Depreciation and amortization 5.6     5.2     16.5 16.2    
Property and revenue taxes 0.0     0.0     0.1 0.1    
Equity in earnings of transmission affiliates 0.0     0.0     0.0 0.0    
Other income, net 11.3     3.7     36.9 20.3    
Interest expense 94.3     90.9     281.3 266.3    
Income tax expense (benefit) 1.0     6.6     (84.0) (73.4)    
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 (81.5)     (95.8)     (166.8) (179.4)    
Capital expenditures, including AFUDC-Debt and asset acquisitions 7.6     6.9     18.7 14.7    
Equity method investments 56.9     55.3     56.9 55.3    
Total assets 1,298.8     1,199.4     1,298.8 1,199.4    
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