v3.26.1
REGULATORY ASSETS AND LIABILITIES - REGULATORY ASSETS (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Regulatory assets    
Total regulatory assets $ 2,948.2 $ 2,941.0
We Power finance leases    
Regulatory assets    
Total regulatory assets 1,164.5 1,158.6
Plant retirement related items    
Regulatory assets    
Total regulatory assets 612.2 634.3
Income tax related items    
Regulatory assets    
Total regulatory assets 448.2 413.3
Pension and OPEB costs    
Regulatory assets    
Total regulatory assets 271.4 289.0
System support resource    
Regulatory assets    
Total regulatory assets 87.5 92.6
Uncollectible expense    
Regulatory assets    
Total regulatory assets 71.1 114.7
Asset retirement obligations    
Regulatory assets    
Total regulatory assets 65.0 59.7
Securitization    
Regulatory assets    
Total regulatory assets 63.6 67.5
Electric transmission costs    
Regulatory assets    
Total regulatory assets 50.0 15.3
Other finance and operating leases    
Regulatory assets    
Total regulatory assets 31.6 25.2
Derivatives    
Regulatory assets    
Total regulatory assets 14.1 9.0
Bluewater Natural Gas Holding, LLC    
Regulatory assets    
Total regulatory assets 10.5 13.9
Other, net    
Regulatory assets    
Total regulatory assets $ 58.5 $ 47.9