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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ 338.1	$ 381.3	$ 764.1	$ 871.2
Natural gas
Disaggregation of Operating Revenues
Revenues from contracts with customers	51.3	61.5	177.0	231.4
Natural gas | Total retail
Disaggregation of Operating Revenues
Revenues from contracts with customers	46.5	43.7	164.6	231.5
Natural gas | Residential
Disaggregation of Operating Revenues
Revenues from contracts with customers	31.3	29.7	107.2	146.7
Natural gas | Commercial and industrial
Disaggregation of Operating Revenues
Revenues from contracts with customers	15.2	14.0	57.4	84.8
Natural gas | Transportation
Disaggregation of Operating Revenues
Revenues from contracts with customers	5.0	4.9	11.8	11.8
Natural gas | Other utility
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ (0.2)	$ 12.9	$ 0.6	$ (11.9)