Schedule I - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Notes to parent company financial statements
Cash received for income taxes, net	$ 27.9	$ (24.9)	$ 16.3
WEC Energy Group
Notes to parent company financial statements
Cash paid for interest	98.5	117.7	102.9
Cash received for income taxes, net	(61.5)	(4.9)	(85.9)
WEC Energy Group \| Wisvest
Notes to parent company financial statements
Settlement of short-term note payable with Wisvest	$ 0.0	$ 0.0	$ 0.9

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