OPERATING REVENUES - DISAGGREGATION OF NATURAL GAS 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, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ 409.6	$ 338.1	$ 907.1	$ 764.1
Natural gas
Disaggregation of Operating Revenues
Revenues from contracts with customers	69.0	51.3	226.6	177.0
Natural gas | Total retail
Disaggregation of Operating Revenues
Revenues from contracts with customers	57.0	46.5	220.8	164.6
Natural gas | Residential
Disaggregation of Operating Revenues
Revenues from contracts with customers	37.1	31.3	139.2	107.2
Natural gas | Commercial and industrial
Disaggregation of Operating Revenues
Revenues from contracts with customers	19.9	15.2	81.6	57.4
Natural gas | Transportation
Disaggregation of Operating Revenues
Revenues from contracts with customers	6.2	5.0	14.8	11.8
Natural gas | Other utility
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ 5.8	$ (0.2)	$ (9.0)	$ 0.6