ACQUISITIONS - UPSTREAM ACQUISITION (Details) - Upstream - Subsequent event $ in Millions	1 Months Ended
	Apr. 30, 2018 USD ($) MW
Business Acquisition [Line Items]
WEC's ownership interest in Upstream Wind Energy Center	80.00%
Capacity of Upstream Wind Energy Center | MW	202.5
Acquisition purchase price | $	$ 276.0
Number of years Upstream will receive fixed payment	10 years
Federal production tax credit percent of published rate	100.00%