Short-Term Debt and Lines of Credit - Credit Facilities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) extension	Dec. 31, 2015 USD ($)
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 2,500.0
Letters of Credit Issued Inside Credit Facilities	19.1
Commercial Paper	860.2	$ 1,095.0
Available capacity under existing agreements	1,620.7
WEC Energy Group
Line of Credit Facility [Line Items]
Commercial Paper	321.8	$ 307.9
WEC Energy Group | Credit facility maturing December 2020
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 1,050.0
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
WE | Credit facility maturing December 2020
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 December 2016
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 250.0
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
WG | Credit facility maturing December 2020
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 December 2020
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
Commercial Paper
Line of Credit Facility [Line Items]
Commercial Paper	$ 860.2