REGULATORY ASSETS AND LIABILITIES - REGULATORY ASSETS (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Regulatory assets
Other current assets	$ 39.9	$ 24.9
Regulatory assets	3,247.0	3,249.8
Total regulatory assets	3,286.9	3,274.7
Pension and OPEB costs
Regulatory assets
Total regulatory assets	728.9	731.7
Plant retirement related items
Regulatory assets
Total regulatory assets	637.8	646.2
Environmental remediation costs
Regulatory assets
Total regulatory assets	583.8	596.8
Income tax related items
Regulatory assets
Total regulatory assets	444.5	449.9
Asset retirement obligations
Regulatory assets
Total regulatory assets	159.8	162.0
Uncollectible expense
Regulatory assets
Total regulatory assets	133.7	127.7
System support resource
Regulatory assets
Total regulatory assets	110.6	113.2
Derivatives
Regulatory assets
Total regulatory assets	88.7	130.3
Decoupling
Regulatory assets
Total regulatory assets	87.2	27.3
Securitization
Regulatory assets
Total regulatory assets	84.1	85.9
Bluewater
Regulatory assets
Total regulatory assets	51.1	45.3
Energy efficiency programs
Regulatory assets
Total regulatory assets	29.3	33.9
Other, net
Regulatory assets
Total regulatory assets	$ 147.4	$ 124.5

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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
-Topic 980
-SubTopic 340
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481878/980-340-50-1

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