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Regulatory Matters - Boswell Mercury Emission Reduction Plan (Details) - Boswell Unit 4 [Member] $ in Millions | Dec. 31, 2015 USD ($)
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Regulatory Matters [Line Items] |
Total Project Costs | $ 220
MPUC [Member] | Boswell Mercury Emissions Reduction Plan [Member] | Minnesota Power [Member] |
Regulatory Matters [Line Items] |
Total Project Costs | $ 220

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