SHORT-TERM DEBT AND LINES OF CREDIT - REVOLVING CREDIT FACILITIES (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 2,500.0
Letters of credit issued inside credit facilities	29.1
Commercial Paper	670.4	$ 860.2
Available capacity under existing agreements	1,800.5
WEC Energy Group | Credit facility maturing December 2020
Line of Credit Facility [Line Items]
Short-term credit capacity	1,050.0
Wisconsin Electric | Credit facility maturing December 2020
Line of Credit Facility [Line Items]
Short-term credit capacity	500.0
WPS | Credit facility maturing December 2020
Line of Credit Facility [Line Items]
Short-term credit capacity	250.0
Wisconsin Gas | Credit facility maturing December 2020
Line of Credit Facility [Line Items]
Short-term credit capacity	350.0
PGL | Credit facility maturing December 2020
Line of Credit Facility [Line Items]
Short-term credit capacity	$ 350.0