REGULATORY ASSETS AND LIABILITIES - REGULATORY ASSETS (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Regulatory assets
Other current assets	$ 12.2	$ 42.3
Regulatory assets	3,313.1	3,264.6
Total regulatory assets	3,325.3	3,306.9
Pension and OPEB costs
Regulatory assets
Total regulatory assets	701.9	714.3
Plant retirement related items
Regulatory assets
Total regulatory assets	677.9	688.6
Environmental remediation costs
Regulatory assets
Total regulatory assets	590.6	610.7
Income tax related items
Regulatory assets
Total regulatory assets	457.5	461.9
Derivatives
Regulatory assets
Total regulatory assets	196.5	133.8
Asset retirement obligations
Regulatory assets
Total regulatory assets	171.1	169.7
System support resource
Regulatory assets
Total regulatory assets	120.9	123.5
Uncollectible expense
Regulatory assets
Total regulatory assets	95.9	69.3
Securitization
Regulatory assets
Total regulatory assets	90.9	92.4
Bluewater
Regulatory assets
Total regulatory assets	31.4	20.9
Energy efficiency programs
Regulatory assets
Total regulatory assets	30.0	33.9
MERC extraordinary natural gas costs
Regulatory assets
Total regulatory assets	21.2	35.1
Other, net
Regulatory assets
Total regulatory assets	$ 139.5	$ 152.8

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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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