RISK MANAGEMENT ACTIVITIES (Details) (Non-hedge derivatives, USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivative assets and liabilities from risk management activities
Other current assets from risk management activities	$ 3.4	$ 1.5
Other current liabilities from risk management activities	6.7	5.1
Other long-term liabilities from risk management activities	4.1	4.4
Natural gas contracts
Derivative assets and liabilities from risk management activities
Other current assets from risk management activities	0.7	0.1
Other current liabilities from risk management activities	0.7	2.5
FTRs
Derivative assets and liabilities from risk management activities
Other current assets from risk management activities	2.7	1.3
Other current liabilities from risk management activities	0.2	0.1
Petroleum product contracts
Derivative assets and liabilities from risk management activities
Other current assets from risk management activities		0.1
Other current liabilities from risk management activities	0.1
Coal contract
Derivative assets and liabilities from risk management activities
Other current liabilities from risk management activities	5.7	2.5
Other long-term liabilities from risk management activities	$ 4.1	$ 4.4