Short-Term Debt and Lines of Credit - Credit Facilities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) extension	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 2,800.0
Commercial paper	1,440.1	$ 1,444.6
Available capacity under existing agreements	1,356.9
WE | Credit facility maturing October 2022
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 500.0
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
WPS | Credit facility maturing October 2022
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 400.0
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
WG | Credit facility maturing October 2022
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 350.0
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
PGL | Credit facility maturing October 2022
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 350.0
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
WEC Energy Group
Line of Credit Facility [Line Items]
Commercial paper	$ 548.4	494.8
WEC Energy Group | Credit facility maturing October 2022
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 1,200.0
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit issued inside credit facilities	$ 3.0
Commercial paper
Line of Credit Facility [Line Items]
Commercial paper	$ 1,440.1	$ 1,444.6