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LONG-TERM DEBT (Details) - USD ($) $ in Millions |  | 1 Months Ended
--- | --- | ---
Oct. 28, 2021 | Jun. 30, 2021 | May 31, 2021 | Mar. 31, 2021 | Mar. 31, 2020
WE | WE 1.70% Debentures due June 15, 2028 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Proceeds from issuance of debt |  | $ 300.0 |  |  |
Interest rate on long-term debt |  | 1.70% |  |  |
WE | WE 2.95% Debentures due September 15, 2021 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Interest rate on long-term debt |  | 2.95% |  |  |
Early repayment of long-term debt |  | $ 300.0 |  |  |
Integrys Holding | Integrys Holding Inc Junior Notes Due 2073 | Subsequent event |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Early repayment of long-term debt | $ 196.4 |  |  |  |
Extinguishment of debt | 178.6 |  |  |  |
Unsecured debt | 400.0 |  |  |  |
Loss on early extinguishment of debt | $ 13.6 |  |  |  |
WEPCo Environmental Trust | WEPCo Environmental Trust Bonds 1.578%, due 2035 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Proceeds from issuance of debt |  |  | $ 118.8 |  |
Interest rate on long-term debt |  |  | 1.578% |  |
WEC Energy Group | Term loan |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Repayments of Short-term Debt |  |  |  | $ 340.0 |
Length of term loan |  |  |  |  | 364 days
WEC Energy Group | WEC Senior Notes 0.80% due 2024 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Proceeds from issuance of debt |  |  |  | $ 600.0 |
Interest rate on long-term debt |  |  |  | 0.80% |

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