GOODWILL AND INTANGIBLES - GOODWILL (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)
Changes to our goodwill balances by segment
Changes to the carrying amount of goodwill	$ 0.0
Goodwill	3,052.8
Accumulated impairment losses	0.0
Wisconsin
Changes to our goodwill balances by segment
Goodwill	2,104.3
Illinois
Changes to our goodwill balances by segment
Goodwill	758.7
Other States
Changes to our goodwill balances by segment
Goodwill	183.2
Non-Utility Energy Infrastructure
Changes to our goodwill balances 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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Amount of increase (decrease) 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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