RISK MANAGEMENT ACTIVITIES - RISK MANAGEMENT ASSETS AND LIABILITIES (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative assets and liabilities from risk management activities
Risk Management Asset	$ 2.3	$ 2.4
Risk Management Liability	7.0	3.1
Non-hedge derivatives
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	2.3	2.2
Long-term assets from risk management activities	0	0.2
Risk Management Asset	2.3	2.4
Current liabilities from risk management activities	5.9	2.3
Long-term liabilities from risk management activities	1.1	0.8
Risk Management Liability	7.0	3.1
Non-hedge derivatives | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	0.1	0.6
Long-term assets from risk management activities	0
Current liabilities from risk management activities	2.1	0.1
Long-term liabilities from risk management activities	0.1
Non-hedge derivatives | FTRs
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	2.2	1.5
Current liabilities from risk management activities	0.3	0.3
Non-hedge derivatives | Petroleum product contracts
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	0	0.1
Current liabilities from risk management activities	1.1	0
Non-hedge derivatives | Coal contract
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	0	0
Long-term assets from risk management activities	0	0.2
Current liabilities from risk management activities	2.4	1.9
Long-term liabilities from risk management activities	$ 1.0	$ 0.8
Designated as hedging instrument
Derivative assets and liabilities from risk management activities
Number of derivative instruments held	0