Schedule I - Short-Term Notes Payable to Related Parties (Details) - WEC Energy Group - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Notes to parent company financial statements
Short-term notes payable to related parties	$ 489.3	$ 398.9
WBS
Notes to parent company financial statements
Short-term notes payable to related parties	168.9	123.5
Integrys
Notes to parent company financial statements
Short-term notes payable to related parties	166.9	139.5
WECC
Notes to parent company financial statements
Short-term notes payable to related parties	111.7	110.3
Bluewater Gas Storage
Notes to parent company financial statements
Short-term notes payable to related parties	$ 41.8	$ 25.6