ACQUISITIONS - BISHOP HILL III (Details) $ in Millions	1 Months Ended
	Aug. 31, 2018 USD ($) MW	Mar. 31, 2019	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
WEC's ownership interest in Bishop Hill III Wind Energy Center		80.00%
Bishop Hill III Wind Energy Center
Business Acquisition [Line Items]
Capacity of Bishop Hill III Wind Energy Center | MW	132
Acquisition purchase price	$ 144.7		$ 18.2
Restricted cash acquired	$ 4.5
Additional Ownership Interest in Bishop Hill III Wind Energy Center			10.00%
Duration of offtake agreement for the sale of energy produced	22 years
Bonus depreciation percentage		100.00%