COMMITMENTS AND CONTINGENCIES - ENVIRONMENTAL MATTERS (Details) $ in Millions	1 Months Ended			3 Months Ended	63 Months Ended
	Apr. 30, 2023 MMBTU	Jan. 31, 2023 micrograms	Dec. 31, 2020 micrograms performance_obligations	Mar. 31, 2023 USD ($) micrograms MW numberOfRevisions	Mar. 31, 2023 USD ($) MW numberOfRevisions	Dec. 31, 2022 USD ($)
Manufactured gas plant remediation
Regulatory assets | $				$ 375.4	$ 375.4	$ 365.5
Environmental remediation costs
Manufactured gas plant remediation
Regulatory assets | $				$ 117.3	$ 117.3	118.5
Cross State Air Pollution Rule - Good Neighbor Plan | Electric | Maximum
Air quality
RICE unit megawatts | MW				25	25
Mercury and Air Toxics Standards | Electric | Subsequent event
Air quality
Current level of particulate matter in pounds per million british thermal unit | MMBTU	0.03
EPA proposed lower limit for particulate matter | MMBTU	0.01
Even lower level of particulate matter that the EPA is seeking opinions on | MMBTU	0.006
National Ambient Air Quality Standards | Electric
Air quality
The EPA issued a draft policy assessment in support of revisiting the decision to make no changes to the 2015 Ozone standards | numberOfRevisions				0	0
Number of revisions necessary to meet the 2012 standard for particulate matter | performance_obligations			0
Current number of micrograms per cubic meter that particulate matter needs to be below			12
Current number of micrograms per cubic meter under 24-hour standard that fine particulate matter needs to be below			35
Lowest limit that will cause non-attainment				10
National Ambient Air Quality Standards | Electric | Maximum
Air quality
Proposed primary (health-based) annual standard		10
The EPA is taking comments on this full range of micrograms per cubic meter				11
New possible number of micrograms per cubic meter that particulate matter may be lowered to				11
National Ambient Air Quality Standards | Electric | Minimum
Air quality
Proposed primary (health-based) annual standard		9
The EPA is taking comments on this full range of micrograms per cubic meter				8
New possible number of micrograms per cubic meter that particulate matter may be lowered to				10
Climate Change | Electric
Air quality
Capacity of coal-fired generation retired, in megawatts | MW					400
Capacity of fossil-fueled generation to be retired by the end of 2026, in megawatts | MW				1,500
Company goal for percent of carbon emission reduction below 2005 levels by the end of 2025				60.00%
Company goal for percentage of carbon emission reduction below 2005 levels by the end of 2030				80.00%
Steam Electric Effluent Limitation Guidelines | Electric
Water quality
Expected capital investment to achieve required discharge limits | $				$ 10.0	$ 10.0
Manufactured Gas Plant Remediation | Natural gas
Manufactured gas plant remediation
Reserves for future environmental remediation | $				84.5	84.5	88.6
Manufactured Gas Plant Remediation | Natural gas | Environmental remediation costs
Manufactured gas plant remediation
Regulatory assets | $				$ 117.3	$ 117.3	$ 118.5