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v3.19.3.a.u2

Derivative Instruments - Cash Flow Hedges (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($) number_of_interest_rate_swaps | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Derivative instruments |  |  |
Total interest expense line item on the income statements | $ 501.5 | $ 445.1 | $ 415.7
Reclassification to interest expense within next 12 months | 1.0 |  |
WEC Energy Group |  |  |
Derivative instruments |  |  |
Total interest expense line item on the income statements | 122.3 | 104.1 | 82.0
WEC Energy Group | WEC Energy Group 2007 Junior Notes due 2067 |  |  |
Derivative instruments |  |  |
Long-term debt outstanding | $ 500.0 |  |
Interest rate swaps | WEC Energy Group |  |  |
Derivative instruments |  |  |
Number of interest rate swaps executed | number_of_interest_rate_swaps | 2 |  |
Interest rate swap notional value | $ 250.0 |  |
Interest rate swap fixed interest rate | 4.9765% |  |
Derivative losses recognized in other comprehensive loss | $ (4.8) | (2.9) | 0.0
Net derivative gains reclassified from accumulated other comprehensive loss to interest expense | $ 1.1 | $ 1.6 | $ 2.2

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