GOODWILL AND INTANGIBLES - GOODWILL (Details) $ in Millions	3 Months Ended
Mar. 31, 2022 USD ($)
Goodwill balance by segment
Changes to the carrying amount of goodwill	$ 0.0
Goodwill	3,052.8
Accumulated impairment losses	0.0
Wisconsin
Goodwill balance by segment
Goodwill	2,104.3
Illinois
Goodwill balance by segment
Goodwill	758.7
Other States
Goodwill balance by segment
Goodwill	183.2
Non-Utility Energy Infrastructure
Goodwill balance by segment
Goodwill	$ 6.6

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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