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REGULATORY MATTERS (Tables) | 9 Months Ended
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Sep. 30, 2025
Regulated Operations [Abstract] |
Schedule of Regulatory Assets and Liabilities | The recovery, refund or credit to rates for these regulatory assets and liabilities will occur over the periods either specified by the applicable regulatory authority or over the corresponding period related to the asset or liability.
Regulatory Assets and Liabilities | September 30, 2025 |  | December 31, 2024 |  |
Millions |  |  |  |  |
Current Regulatory Assets (a) |  |  |  |  |
Fuel Adjustment Clause | $3.6 |  |  | — |  |  |
Other | 1.6 |  |  | $1.6 |  |  |
Total Current Regulatory Assets | $5.2 |  |  | $1.6 |  |  |
Non-Current Regulatory Assets |  |  |  |  |
Defined Benefit Pension and Other Postretirement Benefit Plans | $195.6 |  |  | $200.3 |  |  |
Income Taxes | 78.0 |  |  | 84.9 |  |  |
Asset Retirement Obligations | 44.2 |  |  | 41.0 |  |  |
Cost Recovery Riders | 19.5 |  |  | 5.5 |  |  |
Manufactured Gas Plant | 10.5 |  |  | 11.6 |  |  |
Taconite Harbor | 7.0 |  |  | 17.3 |  |  |
PPACA Income Tax Deferral | 3.6 |  |  | 3.7 |  |  |
Fuel Adjustment Clause | 0.2 |  |  | 4.5 |  |  |
Other | 1.8 |  |  | 2.9 |  |  |
Total Non-Current Regulatory Assets | $360.4 |  |  | $371.7 |  |  |
Current Regulatory Liabilities (b) |  |  |  |  |
Provision for Interim Rate Refund | — |  |  | $23.0 |  |  |
Fuel Adjustment Clause | $0.5 |  |  | 7.2 |  |  |
Other | 1.3 |  |  | 1.3 |  |  |
Total Current Regulatory Liabilities | $1.8 |  |  | $31.5 |  |  |
Non-Current Regulatory Liabilities |  |  |  |  |
Income Taxes | $277.8 |  |  | $292.7 |  |  |
Wholesale and Retail Contra AFUDC | 83.5 |  |  | 77.6 |  |  |
Non-Jurisdictional Land Sales | 81.7 |  |  | 59.7 |  |  |
Plant Removal Obligations | 80.4 |  |  | 74.2 |  |  |
Defined Benefit Pension and Other Postretirement Benefit Plans | 35.5 |  |  | 40.7 |  |  |
Investment Tax Credits | 17.3 |  |  | 17.8 |  |  |
Fuel Adjustment Clause | 7.4 |  |  | 0.6 |  |  |
Boswell Units 1 and 2 Net Plant and Equipment | 6.7 |  |  | 6.7 |  |  |
Other | 3.2 |  |  | 0.5 |  |  |
Total Non-Current Regulatory Liabilities | $593.5 |  |  | $570.5 |  |  |
(a)Current regulatory assets are presented within Prepayments and Other on the Consolidated Balance Sheet. (b)Current regulatory liabilities are presented within Other Current Liabilities on the Consolidated Balance Sheet.

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