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REGULATORY MATTERS (Tables)
3 Months Ended
Mar. 31, 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.
NOTE 2. REGULATORY MATTERS (Continued)

Regulatory Assets and LiabilitiesMarch 31,
2025
December 31,
2024
Millions 
Current Regulatory Assets (a)
  
Fuel Adjustment Clause $2.3 — 
Other1.6 $1.6 
Total Current Regulatory Assets$3.9 $1.6 
Non-Current Regulatory Assets  
Defined Benefit Pension and Other Postretirement Benefit Plans$198.7 $200.3 
Income Taxes83.0 84.9 
Asset Retirement Obligations 42.0 41.0 
Taconite Harbor13.9 17.3 
Manufactured Gas Plant
11.2 11.6 
Cost Recovery Riders8.7 5.5 
PPACA Income Tax Deferral3.7 3.7 
Fuel Adjustment Clause 1.6 4.5 
Other1.8 2.9 
Total Non-Current Regulatory Assets$364.6 $371.7 
Current Regulatory Liabilities (b)
  
Provision for Interim Rate Refund$27.9 $23.0 
Fuel Adjustment Clause4.6 7.2 
Other1.7 1.3 
Total Current Regulatory Liabilities $34.2 $31.5 
Non-Current Regulatory Liabilities  
Income Taxes $287.1 $292.7 
Wholesale and Retail Contra AFUDC 77.9 77.6 
Plant Removal Obligations75.5 74.2 
Non-Jurisdictional Land Sales67.7 59.7 
Defined Benefit Pension and Other Postretirement Benefit Plans39.0 40.7 
Investment Tax Credits17.6 17.8 
Boswell Units 1 and 2 Net Plant and Equipment6.7 6.7 
Fuel Adjustment Clause6.8 0.6 
Other2.3 0.5 
Total Non-Current Regulatory Liabilities$580.6 $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.