DERIVATIVE INSTRUMENTS - GAINS (LOSSES) AND NOTIONAL VOLUMES (Details) MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) MMBTU MWh	Sep. 30, 2022 USD ($) MWh MMBTU	Sep. 30, 2023 USD ($) MMBTU MWh	Sep. 30, 2022 USD ($) MWh MMBTU
Realized gains and losses
Gains (losses)	$ (34.4)	$ 126.5	$ (174.3)	$ 272.3
Natural gas contracts
Realized gains and losses
Gains (losses)	$ (56.3)	$ 119.1	$ (200.7)	$ 259.6
Notional sales volumes
Notional sales volumes | MMBTU	37.8	32.7	144.2	133.3
FTRs and TCRs
Realized gains and losses
Gains (losses)	$ 21.9	$ 7.4	$ 26.4	$ 12.7
Notional sales volumes
Notional sales volumes | MWh	8.1	7.0	22.9	21.0
Non-Utility Energy Infrastructure
Realized gains and losses
Realized gains and losses on derivatives income statement location	Total operating revenues	Total operating revenues	Total operating revenues	Total operating revenues
Utility operations
Realized gains and losses
Realized gains and losses on derivatives income statement location	Cost of sales	Cost of sales	Cost of sales	Cost of sales