Schedule 1 - Guarantees (Details) $ in Millions	Dec. 31, 2021 USD ($)
Notes to parent company financial statements
Total guarantees	$ 97.4
Guarantees expiring in less than one year	15.3
Guarantees expiring within one to three years	0.2
Guarantees with expiration over three years	81.9
Standby letters of credit (1)
Notes to parent company financial statements
Total guarantees	75.2
Guarantees expiring in less than one year	2.5
Guarantees expiring within one to three years	0.2
Guarantees with expiration over three years	72.5
Surety bonds (2)
Notes to parent company financial statements
Total guarantees	12.8
Guarantees expiring in less than one year	12.8
Guarantees expiring within one to three years	0.0
Guarantees with expiration over three years	0.0
Other guarantees (3)
Notes to parent company financial statements
Total guarantees	9.4
Guarantees expiring in less than one year	0.0
Guarantees expiring within one to three years	0.0
Guarantees with expiration over three years	9.4
WEC Energy Group
Notes to parent company financial statements
Total guarantees	938.4
Guarantees expiring in less than one year	829.0
Guarantees expiring within one to three years	1.2
Guarantees with expiration over three years	108.2
WEC Energy Group | UMERC
Notes to parent company financial statements
Total guarantees	6.2
WEC Energy Group | Bluewater
Notes to parent company financial statements
Total guarantees	9.7
WEC Energy Group | WECI
Notes to parent company financial statements
Total guarantees	872.5
WEC Energy Group | Guarantees supporting business operations
Notes to parent company financial statements
Total guarantees	888.4
Guarantees expiring in less than one year	813.7
Guarantees expiring within one to three years	1.2
Guarantees with expiration over three years	73.5
WEC Energy Group | Standby letters of credit (1)
Notes to parent company financial statements
Total guarantees	27.8
Guarantees expiring in less than one year	2.5
Guarantees expiring within one to three years	0.0
Guarantees with expiration over three years	25.3
WEC Energy Group | Surety bonds (2)
Notes to parent company financial statements
Total guarantees	12.8
Guarantees expiring in less than one year	12.8
Guarantees expiring within one to three years	0.0
Guarantees with expiration over three years	0.0
WEC Energy Group | Other guarantees (3)
Notes to parent company financial statements
Total guarantees	9.4
Guarantees expiring in less than one year	0.0
Guarantees expiring within one to three years	0.0
Guarantees with expiration over three years	$ 9.4