DERIVATIVE FINANCIAL INSTRUMENTS AND HEDGING ACTIVITIES (Reclassifications from Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest Rate Contracts	[1]	$ 102.8	$ 93.3	$ 201.7	$ 197.8
Total Reclassifications from AOCI	[1]	197.0	177.7	354.5	350.1
Reclassification out of AOCI [Member] | Accumulated Net (Gain) Loss from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total Reclassifications from AOCI		10.4	9.8	20.7	19.9
Interest Rate Contract [Member] | Reclassification out of AOCI [Member] | Accumulated Net (Gain) Loss from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest Rate Contracts	[2]	$ 10.4	$ 9.8	$ 20.7	$ 19.9

[1] Certain costs that are not allocated to individual segments, including Other, interest expense, allowance for equity used during construction, and income taxes are included in the consolidated total.

[2] Loss reported within “Interest expense, net” in the consolidated statements of income.