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v3.23.3

Operations and Significant Accounting Policies - Other Non-Current Assets (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022 | Sep. 30, 2022 | Dec. 31, 2021
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Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |  |  |
Contract Assets | $ 19.1 | $ 21.0 |  |
Operating Lease Right-of-use Assets | 11.6 | 12.7 |  |
Finance Lease Right-of-use Assets | 2.1 | 0.0 |  |
ALLETE Properties | 19.4 | 19.1 |  |
Restricted Cash | 2.4 | 2.3 | $ 2.3 | $ 2.3
Other Postretirement Benefit Plans | 60.2 | 58.8 |  |
Other | 101.5 | 90.4 |  |
Total Other Non-Current Assets | $ 216.3 | $ 204.3 |  |

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