Schedule I - Cash Dividends Received from Subsidiaries (Details) - WEC Energy Group - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Notes to parent company financial statements
Cash dividends received from subsidiaries	$ 735.3	$ 688.9	$ 548.6
WE
Notes to parent company financial statements
Cash dividends received from subsidiaries	360.0	310.0	240.0
We Power
Notes to parent company financial statements
Cash dividends received from subsidiaries	192.5	223.0	181.0
ATC Holding LLC
Notes to parent company financial statements
Cash dividends received from subsidiaries	87.4	105.8	82.6
WG
Notes to parent company financial statements
Cash dividends received from subsidiaries	60.0	50.0	45.0
WECI
Notes to parent company financial statements
Cash dividends received from subsidiaries	25.4	0.0	0.0
UMERC
Notes to parent company financial statements
Cash dividends received from subsidiaries	10.0	0.0	0.0
Wisvest
Notes to parent company financial statements
Cash dividends received from subsidiaries	$ 0.0	$ 0.1	$ 0.0