OPERATING REVENUES - OTHER NON-UTILITY OPERATING REVENUES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
We Power revenues
Disaggregation of Operating Revenues
Revenues amortized from deferred revenue during the period	$ 5.8	$ 6.3	$ 11.3	$ 12.7
Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues from contracts with customers	1,543.0	1,563.9	3,629.9	3,940.4
Other non-utility revenues | Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues from contracts with customers	18.2	17.2	37.8	35.5
Other non-utility revenues | Revenues from contracts with customers | We Power revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	5.8	6.3	11.3	12.7
Other non-utility revenues | Revenues from contracts with customers | Distributed renewable solar project revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	0.7	0.8	1.1	2.3
Other non-utility revenues | Revenues from contracts with customers | Other
Disaggregation of Operating Revenues
Revenues from contracts with customers	0.2	0.0	0.2	0.1
Transferred over time | Other non-utility revenues | Revenues from contracts with customers | Wind generation revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	7.3	5.9	16.6	12.1
Transferred over time | Other non-utility revenues | Revenues from contracts with customers | Appliance service repairs
Disaggregation of Operating Revenues
Revenues from contracts with customers	$ 4.2	$ 4.2	$ 8.6	$ 8.3