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SHORT-TERM DEBT AND LINES OF CREDIT - SHORT-TERM BORROWINGS (Details) - USD ($) $ in Millions |  | 3 Months Ended |
--- | --- | --- | ---
Mar. 30, 2020 | Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020
Short-term borrowings |  |  |  |
Issuance of term loan |  | $ 0.0 | $ 340.0 |
WEC Senior Notes 0.80% due 2024 | WEC Energy Group |  |  |  |
Short-term borrowings |  |  |  |
Debt instrument stated interest rate percentage |  | 0.80% |  |
Commercial paper |  |  |  |
Short-term borrowings |  |  |  |
Commercial paper outstanding |  | $ 1,580.4 |  | $ 1,436.9
Weighted-average interest rate on amounts outstanding |  | 0.19% |  | 0.21%
Average amount outstanding during the period |  | $ 1,445.3 |  |
Weighted-average interest rate during the period |  | 0.18% |  |
Term loan | WEC Energy Group |  |  |  |
Short-term borrowings |  |  |  |
Term loan outstanding |  | $ 0.0 |  | $ 340.0
Weighted-average interest rate on amounts outstanding |  |  |  | 0.99%
Weighted-average interest rate during the period |  | 0.99% |  |
Issuance of term loan | $ 340.0 |  |  |
Length of term loan | 364 days |  |  |

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