RISK MANAGEMENT ACTIVITIES (Details 8) (Nonregulated segments, Cash flow hedges, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Risk management activities
Unrealized Gain (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)			$ 1.5
Gain (loss) Reclassified from Accumulated OCI into Income	(1.1)	(1.1)	(6.7)
Gain (Loss) Recognized in Income on Derivative Instruments (Ineffective Portion and Amount Excluded from Effectiveness Testing)			0
Natural gas contracts
Risk management activities
Unrealized Gain (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)			(2.3)
Natural gas contracts | Nonregulated revenue
Risk management activities
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	0	(9.3)
Gain (Loss) on Discontinuation of Price Risk Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	0	0	(0.3)
Gain (Loss) Recognized in Income on Derivative Instruments (Ineffective Portion and Amount Excluded from Effectiveness Testing)			0.3
Electric contracts
Risk management activities
Unrealized Gain (Loss) Recognized in OCI on Derivative Instruments (Effective Portion)			3.8
Electric contracts | Nonregulated revenue
Risk management activities
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	0	4.2
Gain (Loss) Recognized in Income on Derivative Instruments (Ineffective Portion and Amount Excluded from Effectiveness Testing)			(0.3)
Interest rate swaps | Interest expense
Risk management activities
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1.1)	(1.1)	(1.1)
Gain (Loss) on Discontinuation of Price Risk Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	$ 0	$ 0	$ (0.2)