OPERATING REVENUES - OTHER NON-UTILITY OPERATING REVENUES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
We Power revenues
Disaggregation of Operating Revenues
Revenues amortized from deferred revenue during the period	$ 6.3	$ 6.2	$ 12.7	$ 12.6
Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues from contracts with customers	1,563.9	1,673.6	3,940.4	3,963.6
Other non-utility revenues | Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues from contracts with customers	17.2	13.0	35.5	24.6
Other non-utility revenues | Revenues from contracts with customers | We Power revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	6.3	6.2	12.7	12.6
Other non-utility revenues | Revenues from contracts with customers | Distributed renewable solar project revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	0.8	2.8	2.3	4.1
Other non-utility revenues | Revenues from contracts with customers | Wind generation revenues
Disaggregation of Operating Revenues
Revenues from contracts with customers	5.9	0.0	12.1	0.0
Other non-utility revenues | Revenues from contracts with customers | Other
Disaggregation of Operating Revenues
Revenues from contracts with customers	0.0	0.1	0.1	0.1
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	$ 3.9	$ 8.3	$ 7.8