Schedule 1 - Guarantees (Details) $ in Millions	Dec. 31, 2024 USD ($)
Notes to parent company financial statements
Total guarantees	$ 221.4
Guarantees expiring in less than one year	53.7
Guarantees expiring within one to three years	30.1
Guarantees with expiration over three years	137.6
Standby letters of credit
Notes to parent company financial statements
Total guarantees	176.1
Guarantees expiring in less than one year	19.8
Guarantees expiring within one to three years	30.0
Guarantees with expiration over three years	126.3
Surety bonds
Notes to parent company financial statements
Total guarantees	34.0
Guarantees expiring in less than one year	33.9
Guarantees expiring within one to three years	0.1
Guarantees with expiration over three years	0.0
Other guarantees
Notes to parent company financial statements
Total guarantees	11.3
Guarantees expiring in less than one year	0.0
Guarantees expiring within one to three years	0.0
Guarantees with expiration over three years	11.3
WEC Energy Group
Notes to parent company financial statements
Total guarantees	411.6
Guarantees expiring in less than one year	112.4
Guarantees expiring within one to three years	35.9
Guarantees with expiration over three years	263.3
WEC Energy Group | WECI
Notes to parent company financial statements
Total guarantees	178.8
WEC Energy Group | MERC
Notes to parent company financial statements
Total guarantees	30.5
WEC Energy Group | MGU
Notes to parent company financial statements
Total guarantees	13.0
WEC Energy Group | Bluewater
Notes to parent company financial statements
Total guarantees	10.2
WEC Energy Group | NSG
Notes to parent company financial statements
Total guarantees	3.0
WEC Energy Group | UMERC
Notes to parent company financial statements
Total guarantees	2.0
WEC Energy Group | Guarantees supporting business operations
Notes to parent company financial statements
Total guarantees	237.5
Guarantees expiring in less than one year	58.7
Guarantees expiring within one to three years	5.8
Guarantees with expiration over three years	173.0
WEC Energy Group | Standby letters of credit
Notes to parent company financial statements
Total guarantees	128.8
Guarantees expiring in less than one year	19.8
Guarantees expiring within one to three years	30.0
Guarantees with expiration over three years	79.0
WEC Energy Group | Surety bonds
Notes to parent company financial statements
Total guarantees	34.0
Guarantees expiring in less than one year	33.9
Guarantees expiring within one to three years	0.1
Guarantees with expiration over three years	0.0
WEC Energy Group | Other guarantees
Notes to parent company financial statements
Total guarantees	11.3
Guarantees expiring in less than one year	0.0
Guarantees expiring within one to three years	0.0
Guarantees with expiration over three years	$ 11.3