Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Short-Term Debt and Lines of Credit - Outstanding Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Issuance of short-term loan	$ 340.0	$ 0.0	$ 0.0
WE
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
WPS
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
WG
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
PGL
Short-term Debt [Line Items]
Maximum debt to capitalization ratio	65.00%
WEC Energy Group
Short-term Debt [Line Items]
Commercial paper outstanding	$ 820.4	334.7
Issuance of short-term loan	$ 340.0	0.0	$ 0.0
Maximum debt to capitalization ratio	70.00%
Commercial paper
Short-term Debt [Line Items]
Commercial paper outstanding	$ 1,436.9	$ 830.8
Average interest rate on amount outstanding	0.21%	2.00%
Average amount outstanding during the year	$ 788.9
Weighted- average interest rate during the year	0.85%
Term loan
Short-term Debt [Line Items]
Average interest rate on amount outstanding	0.99%	0.00%
Term loan outstanding	$ 340.0	$ 0.0
Weighted- average interest rate during the year	1.38%
Issuance of short-term loan	$ 340.0
Length of term loan	364 days