REGULATORY ASSETS AND LIABILITIES - PLANT RETIREMENTS (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Oak Creek Power Plant Units 5 and 6
Regulatory assets	$ 3,435.0	$ 3,274.7
Regulatory liability	3,894.6	3,745.2
Removal costs
Oak Creek Power Plant Units 5 and 6
Regulatory liability	1,401.5	1,329.9
Plant retirement related items
Oak Creek Power Plant Units 5 and 6
Regulatory assets	824.6	$ 646.2
Oak Creek Power Plant Units 5 and 6
Oak Creek Power Plant Units 5 and 6
Deferred tax liabilities	9.4
Oak Creek Power Plant Units 5 and 6 \| Removal costs
Oak Creek Power Plant Units 5 and 6
Regulatory liability	43.9
Oak Creek Power Plant Units 5 and 6 \| Plant retirement related items
Oak Creek Power Plant Units 5 and 6
Regulatory assets	$ 78.3

Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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