PROPERTY, PLANT, AND EQUIPMENT - PUBLIC SERVICE BUILDING AND STEAM TUNNEL ASSETS (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2020
Property, plant, and equipment
Insurance proceeds received for property damage	$ 41.0	$ 0.0
WE \| Public Service Building and Steam Tunnel Assets
Property, plant, and equipment
Costs incurred for repairs and restorations	95.3
Insurance proceeds received for property damage	41.0		$ 20.0
Costs included in other operation and maintenance			$ 12.5
Repairs and restorations to be recovered through rates	$ 21.8

Amount of cash inflow for proceeds from settlement of insurance claim, classified as investing activities. Excludes insurance settlement classified as operating activities.

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