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

$ 482.2

$ 465.6

$ 1,451.8

$ 1,372.7

Electric

Disaggregation of Operating Revenues

Revenues from contracts with customers

445.6

416.3

1,147.6

1,096.8

Electric | Total retail

Disaggregation of Operating Revenues

Revenues from contracts with customers

404.7

373.9

1,050.3

991.1

Electric | Residential

Disaggregation of Operating Revenues

Revenues from contracts with customers

160.1

146.4

425.6

399.1

Electric | Small commercial and industrial

Disaggregation of Operating Revenues

Revenues from contracts with customers

146.0

135.5

377.2

357.1

Electric | Large commercial and industrial customers

Disaggregation of Operating Revenues

Revenues from contracts with customers

96.4

89.9

240.8

228.4

Electric | Other

Disaggregation of Operating Revenues

Revenues from contracts with customers

2.2

2.1

6.7

6.5

Electric | Wholesale

Disaggregation of Operating Revenues

Revenues from contracts with customers

17.9

17.4

49.2

45.8

Electric | Resale

Disaggregation of Operating Revenues

Revenues from contracts with customers

17.2

20.5

35.2

47.4

Electric | Other utility

Disaggregation of Operating Revenues

Revenues from contracts with customers

$ 5.8

$ 4.5

$ 12.9

$ 12.5