FAIR VALUE MEASUREMENTS - FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Carrying amount
Financial instruments
Long-term debt, including current portion	$ 2,258.9	$ 2,258.0
Fair value
Financial instruments
Long-term debt, including current portion	$ 1,935.7	$ 1,882.1

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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+ Details

WISCONSIN PUBLIC SERVICE CORP 10-Q