OPERATING REVENUES - OTHER NON-UTILITY OPERATING REVENUES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Operating Revenues
Revenues	$ 1,672.5	$ 1,631.5	$ 3,959.0	$ 3,936.0
We Power revenues
Disaggregation of Operating Revenues
Revenues amortized from deferred revenue during the period	6.2		$ 12.6
Appliance service repairs | Maximum
Disaggregation of Operating Revenues
Duration of contract for remaining performance obligations in contract			1 year
Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues	1,673.6		$ 3,963.6
Other non-utility revenues | Revenues from contracts with customers
Disaggregation of Operating Revenues
Revenues	13.0		24.6
Other non-utility revenues | Revenues from contracts with customers | We Power revenues
Disaggregation of Operating Revenues
Revenues	6.2		12.6
Other non-utility revenues | Revenues from contracts with customers | Distributed renewable solar project revenues
Disaggregation of Operating Revenues
Revenues	2.8		4.1
Other non-utility revenues | Revenues from contracts with customers | Other
Disaggregation of Operating Revenues
Revenues	0.1		0.1
Transferred over time | Other non-utility revenues | Revenues from contracts with customers | Appliance service repairs
Disaggregation of Operating Revenues
Revenues	$ 3.9		$ 7.8