Schedule I - Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Carrying amount
Notes to parent company financial statements
Long-term debt, including current portion	$ 13,563.4	$ 12,450.5
Fair value
Notes to parent company financial statements
Long-term debt, including current portion	14,819.4	14,343.2
Long-term debt, including current portion	13,563.4	12,450.5
WEC Energy Group | Carrying amount
Notes to parent company financial statements
Long-term debt, including current portion	3,549.8	2,754.8
WEC Energy Group | Fair value
Notes to parent company financial statements
Long-term debt, including current portion	$ 3,546.9	$ 2,836.9