Long-Term Debt - Debt Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2023	Aug. 15, 2023	Jul. 01, 2023	Dec. 31, 2022	Nov. 15, 2021
Long-term debt
Total	$ 16,724.3			$ 15,559.8
Integrys acquisition fair value adjustment	0.0			1.2
Long-term debt, including current portion	16,631.1			15,464.2
Unamortized debt issuance costs	(80.2)			(81.8)
Unamortized discount, net and other	(20.5)			(22.3)
Current portion of long-term debt	(1,264.2)			(808.5)
Long-term debt	15,366.9			14,655.7
Finance lease obligation	$ 145.9			$ 183.2
WE
Long-term debt
Weighted average interest rate	4.22%			4.22%
Unsecured debt	$ 3,285.0			$ 3,285.0
WEPCo Environmental Trust Finance I, LLC
Long-term debt
Weighted average interest rate	1.58%			1.58%
Secured debt	$ 97.0			$ 105.9
WPS
Long-term debt
Weighted average interest rate	4.11%			4.11%
Senior notes	$ 1,975.0			$ 1,975.0
WG
Long-term debt
Weighted average interest rate	3.35%			3.35%
Unsecured debt	$ 790.0			$ 790.0
Integrys | 6.00% Integrys junior notes
Long-term debt
Weighted average interest rate	0.00%			6.00%
Unsecured debt	$ 0.0			$ 221.4
PGL
Long-term debt
Weighted average interest rate	3.53%			3.41%
Secured debt	$ 2,070.0			$ 1,970.0
PGL | Collateralized First Mortgage Bonds
Long-term debt
Secured debt	$ 100.0
NSG
Long-term debt
Weighted average interest rate	3.81%			3.56%
Secured debt	$ 177.0			$ 157.0
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	3.18%			3.18%
Senior notes	$ 150.0			$ 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	3.76%			3.76%
Senior notes	$ 109.8			$ 112.6
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	5.65%			5.62%
Secured debt	$ 856.4			$ 896.5
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	$ 307.7			$ 332.1
WECI Wind Holding II
Long-term debt
Weighted average interest rate	6.38%			6.38%
Senior notes	$ 191.4			$ 199.3
Jayhawk Wind LLC
Long-term debt
Long-term debt, including current portion	$ 7.5			$ 7.3
WEC Energy Group
Long-term debt
Weighted average interest rate	3.68%			2.44%
Senior notes	$ 5,320.0			$ 3,970.0
Current portion of long-term debt	(600.0)			(700.0)
Long-term debt	$ 5,192.8			$ 3,747.2
WEC Energy Group | WEC Energy Group junior notes due 2067
Long-term debt
Weighted average interest rate	7.75%			6.72%
Unsecured debt	$ 500.0	$ 500.0	$ 500.0	$ 500.0	$ 500.0
Interest rate	7.75%			6.72%
WEC Energy Group | 6.20% WEC Energy Group senior notes
Long-term debt
Interest rate	6.20%