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Long-Term Debt - Debt Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2024	May 31, 2024	Feb. 07, 2024	Dec. 31, 2023
Long-term debt
Total	$ 19,023.9			$ 16,724.3
Long-term debt, including current portion	18,907.1			16,631.1
Unamortized debt issuance costs	(103.2)			(80.2)
Unamortized discount, net and other	(21.1)			(20.5)
Current portion of long-term debt	(1,729.0)			(1,264.2)
Long-term debt	$ 17,178.1			$ 15,366.9
WE
Long-term debt
Weighted average interest rate	4.55%			4.22%
Unsecured debt	$ 3,935.0			$ 3,285.0
WEPCo Environmental Trust Finance I, LLC
Long-term debt
Weighted average interest rate	1.58%			1.58%
Secured debt	$ 88.0			$ 97.0
WPS
Long-term debt
Weighted average interest rate	4.17%			4.11%
Senior notes	$ 2,275.0			$ 1,975.0
WG
Long-term debt
Weighted average interest rate	3.92%			3.35%
Unsecured debt	$ 840.0			$ 790.0
PGL
Long-term debt
Weighted average interest rate	3.56%			3.53%
Secured debt	$ 1,995.0			$ 2,070.0
PGL \| Collateralized First Mortgage Bonds
Long-term debt
Secured debt	$ 100.0
NSG
Long-term debt
Weighted average interest rate	3.81%			3.81%
Secured debt	$ 177.0			$ 177.0
MERC
Long-term debt
Weighted average interest rate	3.04%			3.04%
Senior notes	$ 210.0			$ 210.0
MGU
Long-term debt
Weighted average interest rate	3.45%			3.18%
Senior notes	$ 175.0			$ 150.0
UMERC
Long-term debt
Weighted average interest rate	3.26%			3.26%
Senior notes	$ 160.0			$ 160.0
Bluewater Gas Storage
Long-term debt
Weighted average interest rate	4.07%			3.76%
Senior notes	$ 131.9			$ 109.8
ATC Holding LLC
Long-term debt
Weighted average interest rate	4.05%			4.05%
Senior notes	$ 475.0			$ 475.0
We Power
Long-term debt
Weighted average interest rate	5.67%			5.65%
Secured debt	$ 814.3			$ 856.4
WECC
Long-term debt
Weighted average interest rate	6.94%			6.94%
Unsecured debt	$ 50.0			$ 50.0
WECI Wind Holding I
Long-term debt
Weighted average interest rate	2.75%			2.75%
Senior notes	$ 246.4			$ 307.7
WECI Wind Holding II
Long-term debt
Weighted average interest rate	6.38%			6.38%
Senior notes	$ 167.6			$ 191.4
WECI Energy Holding III
Long-term debt
Weighted average interest rate	5.73%			0.00%
Senior notes	$ 488.7			$ 0.0
Jayhawk Wind LLC
Long-term debt
Long-term debt, including current portion	$ 7.5			$ 7.5
WEC Energy Group
Long-term debt
Weighted average interest rate	4.13%			3.68%
Senior notes	$ 6,045.0			$ 5,320.0
Current portion of long-term debt	(620.0)			(600.0)
Long-term debt	$ 6,135.4			$ 5,192.8
WEC Energy Group \| WEC Energy Group junior notes due 2067
Long-term debt
Weighted average interest rate				7.75%
Unsecured debt		$ 377.9	$ 500.0	$ 500.0
Interest rate				7.75%
WEC Energy Group \| 2024 Junior Notes
Long-term debt
Weighted average interest rate	6.72%
Unsecured debt	$ 750.0
WEC Energy Group \| 2024A Junior Notes due June 15, 2055
Long-term debt
Interest rate	6.69%
WEC Energy Group \| 2024B Junior Notes due June 15, 2055
Long-term debt
Interest rate	6.74%