OPERATING REVENUES - OTHER NON-UTILITY OPERATING REVENUES (Details) - Revenues from contracts with customers - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ 2,669.0	$ 2,086.9
We Power revenues
Disaggregation of Operating Revenues
Revenues amortized from deferred revenue during the period	5.8	5.5
Other non-utility revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	26.3	19.6
Other non-utility revenues | We Power revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	5.8	5.5
Other non-utility revenues | Distributed renewable solar project revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	0.0	0.4
Transferred over time | Other non-utility revenues | Wind generation revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	15.8	9.3
Transferred over time | Other non-utility revenues | Appliance service repairs
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ 4.7	$ 4.4