Schedule I - Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 16.3	$ 24.8	$ 37.5
Other	253.4	63.4
Current assets	2,656.7	2,083.0
Long-term assets
Other	361.1	295.6
Long-term assets	36,331.8	34,945.1
Total assets	38,988.5	37,028.1	34,951.8
Current liabilities
Other	680.9	704.7
Current liabilities	3,753.0	4,148.1
Long-term liabilities
Long-term debt	13,472.4	11,672.8
Other	1,203.2	1,229.4
Long-term liabilities	24,122.2	22,217.5
Equity
Total liabilities and equity	38,988.5	37,028.1
WEC Energy Group
Current assets
Cash and cash equivalents	0.5	4.0	$ 0.5	$ 32.8
Accounts receivable from related parties	0.6	0.7
Notes receivable from related parties	29.0	110.8
Prepaid taxes	56.5	54.4
Other	0.1	0.1
Current assets	86.7	170.0
Long-term assets
Investments in subsidiaries	15,365.4	14,248.3
Other	21.8	15.7
Long-term assets	15,387.2	14,264.0
Total assets	15,473.9	14,434.0
Current liabilities
Short-term debt	736.1	820.4
Accounts payable to related parties	5.5	31.7
Notes payable to related parties	220.4	303.0
Other	21.5	19.6
Current liabilities	983.5	1,174.7
Long-term liabilities
Long-term debt	3,549.8	2,754.8
Other	27.4	34.8
Long-term liabilities	3,577.2	2,789.6
Equity
Common shareholders' equity	10,913.2	10,469.7
Total liabilities and equity	$ 15,473.9	$ 14,434.0