ACQUISITIONS - UPSTREAM ACQUISITION (Details) - Upstream $ in Millions	3 Months Ended
	Mar. 31, 2019 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	$ 268.2
Cash and restricted cash acquired	$ 9.2
Number of years Upstream will receive fixed payment	10 years
Bonus depreciation percentage	100.00%