Acquisitions - Upstream (Details) - Upstream Wind Energy Center [Member] $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) MW
Business Acquisition [Line Items]
Number of years Upstream will receive fixed payment	10 years
Capacity of Upstream Wind Energy Center | MW	202.5
Acquisition purchase price | $	$ 276.0
Bonus depreciation percentage	100.00%
WEC's ownership interest in Upstream Wind Energy Center	80.00%