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LONG-TERM DEBT (Details) - USD ($) $ in Millions		1 Months Ended
LONG-TERM DEBT (Details) - USD ($) $ in Millions	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%