LONG-TERM DEBT (Details)		1 Months Ended				3 Months Ended			9 Months Ended
	Feb. 07, 2024 USD ($)	Oct. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	May 31, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($) d $ / shares	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) shares	Sep. 30, 2023 USD ($)
Debt Instrument [Line Items]
Interest expense						$ 204,200,000		$ 182,500,000	$ 596,800,000	$ 533,400,000
5.00% WE Debentures due 05/15/2029 | WE
Debt Instrument [Line Items]
Interest rate on long-term debt				5.00%
Proceeds from issuance of debt				$ 350,000,000.0
4.60% WE Debentures due 10/01/2034 | WE
Debt Instrument [Line Items]
Interest rate on long-term debt			4.60%			4.60%			4.60%
Proceeds from issuance of debt			$ 300,000,000.0
5.05% WE Debentures due 10/01/2054 | WE
Debt Instrument [Line Items]
Interest rate on long-term debt			5.05%			5.05%			5.05%
Proceeds from issuance of debt			$ 300,000,000.0
4.86% WG Debentures due 11/01/2029 | WE | Subsequent event
Debt Instrument [Line Items]
Interest rate on long-term debt		4.86%
4.86% WG Debentures due 11/01/2029 | WG | Subsequent event
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 100,000,000.0
5.18% WG Debentures due 11/01/2034 | WE | Subsequent event
Debt Instrument [Line Items]
Interest rate on long-term debt		5.18%
5.18% WG Debentures due 11/01/2034 | WG | Subsequent event
Debt Instrument [Line Items]
Proceeds from issuance of debt		$ 100,000,000
4.85% MGU Senior Notes due 11/01/2029 | MGU | Subsequent event
Debt Instrument [Line Items]
Interest rate on long-term debt		4.85%
Proceeds from issuance of debt		$ 10,000,000.0
5.23% MGU Senior Notes due 11/01/2034 | MGU | Subsequent event
Debt Instrument [Line Items]
Interest rate on long-term debt		5.23%
Proceeds from issuance of debt		$ 15,000,000.0
5.41% Bluewater Senior Notes due 11/01/2041 | Bluewater | Subsequent event
Debt Instrument [Line Items]
Interest rate on long-term debt		5.41%
Proceeds from issuance of debt		$ 25,000,000.0
WEC Energy Group | Floating Rate WEC Energy Group Junior Notes Due 2067
Debt Instrument [Line Items]
Extinguishment of debt	$ 122,100,000			19,000,000.0
Unsecured debt	500,000,000			377,900,000
Repayment of long-term debt	115,200,000			$ 18,700,000
Gain on early extinguishment of debt	$ 6,900,000
WEC Energy Group | WEC 0.80% Senior Notes $600M due March 15, 2024
Debt Instrument [Line Items]
Repayment of long-term debt					$ 600,000,000.0
Interest rate on long-term debt					0.80%
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2027
Debt Instrument [Line Items]
Interest rate on long-term debt							4.375%
Proceeds from issuance of debt							$ 862,500,000
Initial conversion ratio							10.1243
Principal amount conversion rate applied to							$ 1,000
Initial conversion price, per share | $ / shares							$ 98.77
Senior Notes			862,500,000			$ 862,500,000			$ 862,500,000
Unamortized debt issuance costs			(8,800,000)			(8,800,000)			(8,800,000)
Net carrying amount			853,700,000			853,700,000			853,700,000
Fair value amount			936,300,000			936,300,000			936,300,000
Contractual interest expense						9,400,000			12,900,000
Amortization of debt issuance costs						800,000			1,100,000
Interest expense						10,200,000			$ 14,000,000.0
Number of shares outstanding related to the potential conversion of the Notes included in diluted eps | shares									0
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2027 | Early redemption terms
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage							100.00%
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2027 | Debt conversion terms one
Debt Instrument [Line Items]
Threshold percentage of trigger							130.00%
Trading days | d							20
Consecutive trading days | d							30
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2027 | Debt conversion terms two
Debt Instrument [Line Items]
Threshold percentage of trigger							98.00%
Trading days | d							5
Consecutive trading days | d							10
Principal amount conversion rate applied to							$ 1,000
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2027 | Debt conversion terms four
Debt Instrument [Line Items]
Trading days prior to maturity | d							2
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2029
Debt Instrument [Line Items]
Interest rate on long-term debt							4.375%
Proceeds from issuance of debt							$ 862,500,000
Initial conversion ratio							10.1243
Principal amount conversion rate applied to							$ 1,000
Initial conversion price, per share | $ / shares							$ 98.77
Senior Notes			862,500,000			862,500,000			$ 862,500,000
Unamortized debt issuance costs			(9,300,000)			(9,300,000)			(9,300,000)
Net carrying amount			853,200,000			853,200,000			853,200,000
Fair value amount			$ 954,700,000			954,700,000			954,700,000
Contractual interest expense						9,400,000			12,900,000
Amortization of debt issuance costs						500,000			700,000
Interest expense						$ 9,900,000			$ 13,600,000
Number of shares outstanding related to the potential conversion of the Notes included in diluted eps | shares									0
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2029 | Early redemption terms
Debt Instrument [Line Items]
Trading days prior to early redemption | d							41
Threshold percentage of trigger							130.00%
Trading days | d							20
Consecutive trading days | d							30
Debt instrument, redemption price, percentage							100.00%
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2029 | Debt conversion terms one
Debt Instrument [Line Items]
Threshold percentage of trigger							130.00%
Trading days | d							20
Consecutive trading days | d							30
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2029 | Debt conversion terms two
Debt Instrument [Line Items]
Threshold percentage of trigger							98.00%
Trading days | d							5
Consecutive trading days | d							10
Principal amount conversion rate applied to							$ 1,000
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2029 | Debt conversion terms three
Debt Instrument [Line Items]
Trading days prior to redemption | d							2
WEC Energy Group | WEC 4.375% Convertible Notes due June 1, 2029 | Debt conversion terms four
Debt Instrument [Line Items]
Trading days prior to maturity | d							2