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

6 Months Ended

Jun. 30, 2026

Jun. 30, 2025

Jun. 30, 2026

Jun. 30, 2025

Disaggregation of Operating Revenues

Revenues from contracts with customers

$ 406.5

$ 409.6

$ 969.6

$ 907.1

Electric

Disaggregation of Operating Revenues

Revenues from contracts with customers

341.6

340.6

702.0

680.5

Electric | Total retail

Disaggregation of Operating Revenues

Revenues from contracts with customers

317.2

308.2

645.6

617.2

Electric | Residential

Disaggregation of Operating Revenues

Revenues from contracts with customers

125.3

120.7

265.5

252.7

Electric | Small commercial and industrial

Disaggregation of Operating Revenues

Revenues from contracts with customers

115.3

112.6

231.2

221.6

Electric | Large commercial and industrial customers

Disaggregation of Operating Revenues

Revenues from contracts with customers

74.3

72.6

144.4

138.5

Electric | Other

Disaggregation of Operating Revenues

Revenues from contracts with customers

2.3

4.5

4.4

Electric | Wholesale

Disaggregation of Operating Revenues

Revenues from contracts with customers

15.6

14.8

31.3

28.4

Electric | Resale

Disaggregation of Operating Revenues

Revenues from contracts with customers

5.7

13.5

18.0

26.9

Electric | Other utility

Disaggregation of Operating Revenues

Revenues from contracts with customers

$ 3.1

$ 4.1

$ 7.1

$ 8.0