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COMMITMENTS AND CONTINGENCIES (Narrative) (Details) - USD ($) $ in Millions | Mar. 31, 2018 | Jan. 01, 2018 | Dec. 31, 2017
--- | --- | --- | ---
Loss Contingencies [Line Items] |  |  |
Loss Contingency Accrual | $ 5.0 |  |
Loans to and accounts receivable from the Canadian Entities | 50.4 | $ 51.6 | $ 51.6
Contingent claims | 54.3 | $ 55.6 | $ 55.6
Michigan Electricity Matters [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Loss Contingency Accrual | $ 13.0 |  |

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- Details
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