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Schedule I - Fair Value Measurements (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Carrying amount |  |
Financial instruments |  |
Long-term debt, including current portion | $ 9,561.7 | $ 9,285.8
Fair value |  |
Financial instruments |  |
Long-term debt, including current portion | 10,341.9 | 9,818.2
WEC Energy Group |  |
Financial instruments |  |
Long-term note receivable from UMERC | 50.0 | 0.0
WEC Energy Group | Carrying amount |  |
Financial instruments |  |
Long-term note receivable from UMERC | 50.0 | 0.0
Long-term debt, including current portion | 1,892.3 | 1,890.0
WEC Energy Group | Fair value |  |
Financial instruments |  |
Long-term note receivable from UMERC | 49.5 | 0.0
Long-term debt, including current portion | $ 1,941.5 | $ 1,906.1

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