Long-Term Debt - Debt Outstanding (Details) $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($) number_of_interest_rate_swaps	Dec. 31, 2020 USD ($)	Jul. 12, 2018 number_of_interest_rate_swaps
Long-term debt
Total	$ 13,652.6	$ 12,529.2
Integrys acquisition fair value adjustment	2.9	8.4
Long-term debt, including current portion	13,563.4	12,450.5
Unamortized debt issuance costs	(77.7)	(65.2)
Unamortized discount, net and other	(21.7)	(21.9)
Current portion of long-term debt	(91.0)	(777.7)
Long-term debt	13,472.4	11,672.8
Total Liabilities
Long-term debt
Finance lease obligation	$ 129.7	$ 63.4
WE
Long-term debt
Weighted average interest rate	4.13%	4.26%
Unsecured debt	$ 2,785.0	$ 2,785.0
WEPCo Environmental Trust Finance I, LLC
Long-term debt
Weighted average interest rate	1.58%
Secured debt	$ 114.7	$ 0.0
WPS
Long-term debt
Weighted average interest rate	3.89%	4.04%
Senior notes	$ 1,675.0	$ 1,625.0
WG
Long-term debt
Weighted average interest rate	3.35%	3.65%
Unsecured debt	$ 790.0	$ 640.0
Integrys \| 6.00% Integrys junior notes
Long-term debt
Weighted average interest rate	6.00%	6.00%
Unsecured debt	$ 221.4	$ 400.0
Basis points added to three-month LIBOR rate	3.22%
PGL
Long-term debt
Weighted average interest rate	3.31%	3.45%
Secured debt	$ 1,870.0	$ 1,670.0
PGL \| Collateralized First Mortgage Bonds
Long-term debt
Secured debt	$ 100.0
NSG
Long-term debt
Weighted average interest rate	3.56%	3.81%
Secured debt	$ 157.0	$ 132.0
MERC
Long-term debt
Weighted average interest rate	3.04%	3.27%
Senior notes	$ 210.0	$ 170.0
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	$ 115.2	$ 117.8
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	5.60%	5.59%
Secured debt	$ 934.7	$ 970.8
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	$ 374.6	$ 413.6
Jayhawk Wind LLC
Long-term debt
Long-term debt, including current portion	$ 7.3	$ 0.0
WEC Energy Group
Long-term debt
Weighted average interest rate	1.67%	2.03%
Senior notes	$ 3,070.0	$ 2,270.0
Long-term debt	$ 3,549.8	$ 2,754.8
WEC Energy Group \| WEC Energy Group junior notes due 2067
Long-term debt
Weighted average interest rate	2.27%	3.65%
Unsecured debt	$ 500.0	$ 500.0
Interest rate	2.27%	2.33%
WEC Energy Group \| 6.20% WEC Energy Group senior notes
Long-term debt
Interest rate	6.20%
WEC Energy Group \| Interest rate swaps
Long-term debt
Number of interest rate swaps executed \| number_of_interest_rate_swaps	2		2
Interest rate swap fixed interest rate	4.9765%
Interest rate swap notional value	$ 250.0

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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