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Schedule I - Long-Term Debt (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Future maturities of long-term debt outstanding |  |
2018 | $ 838.4 |
2020 | 686.9 |
Thereafter | 7,336.0 |
Total | 9,600.9 |
Long-term notes outstanding | 8,746.6 | $ 9,158.2
WEC Energy Group |  |
Future maturities of long-term debt outstanding |  |
2018 | 300.0 |
2020 | 400.0 |
Thereafter | 1,200.0 |
Total | 1,900.0 |
Long-term notes outstanding | 1,592.3 | $ 1,890.0
WEC Energy Group | WECC | Support Agreement Related to WECC Debt |  |
Future maturities of long-term debt outstanding |  |
Long-term notes outstanding | $ 50.0 |

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