OPERATING REVENUES - DISAGGREGATION OF ELECTRIC UTILITY OPERATING REVENUES BY CUSTOMER CLASS (Details) - Revenues from contracts with customers - Utility segment - Transferred over time - USD ($)
$ in Millions

3 Months Ended

9 Months Ended

Sep. 30, 2026

Sep. 30, 2025

Sep. 30, 2026

Sep. 30, 2025

Disaggregation of Operating Revenues

Revenues from contracts with customers

$ 1,324.3

$ 1,199.9

$ 3,681.0

$ 3,382.1

Electric

Disaggregation of Operating Revenues

Revenues from contracts with customers

1,275.5

1,146.7

3,255.0

3,003.3

Electric | Total retail

Disaggregation of Operating Revenues

Revenues from contracts with customers

1,167.5

1,066.5

3,002.7

2,779.3

Electric | Residential

Disaggregation of Operating Revenues

Revenues from contracts with customers

540.4

501.3

1,355.5

1,285.6

Electric | Small commercial and industrial

Disaggregation of Operating Revenues

Revenues from contracts with customers

379.4

357.8

1,033.4

971.0

Electric | Large commercial and industrial

Disaggregation of Operating Revenues

Revenues from contracts with customers

242.9

202.3

598.6

507.0

Electric | Other

Disaggregation of Operating Revenues

Revenues from contracts with customers

4.8

5.1

15.2

15.7

Electric | Wholesale

Disaggregation of Operating Revenues

Revenues from contracts with customers

11.1

13.4

37.3

38.4

Electric | Resale

Disaggregation of Operating Revenues

Revenues from contracts with customers

90.0

61.1

185.8

159.6

Electric | Steam

Disaggregation of Operating Revenues

Revenues from contracts with customers

3.4

2.9

22.6

20.6

Electric | Other utility

Disaggregation of Operating Revenues

Revenues from contracts with customers

$ 3.5

$ 2.8

$ 6.6

$ 5.4