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OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES - Other Non-Current Liabilities (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Business Segments [Line Items] |  |
Asset Retirement Obligation | $ 263.6 | $ 261.3
PSAs | 10.7 | 15.1
Other | 37.8 | 36.4
Total Other Non-Current Liabilities | 312.1 | 312.8
BNI Energy |  |
Business Segments [Line Items] |  |
Other receivables | $ 42.3 | $ 42.3

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