RISK MANAGEMENT ACTIVITIES (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	$ 181.8	$ 145.4
Long-term Assets from Risk Management Activities	62.1	45.3
Current Liabilities from Risk Management Activities	198.1	181.9
Long-term Liabilities from Risk Management Activities	64.3	58.4
Risk Management Liabilities	262.4	240.3
Risk Management Assets	243.9	190.7
Utility Segments | Non-hedge derivatives | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	2.0	2.5
Long-term Assets from Risk Management Activities	0.6	0.9
Current Liabilities from Risk Management Activities	6.8	14.0
Long-term Liabilities from Risk Management Activities	0.7	0.8
Utility Segments | Non-hedge derivatives | FTRs
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	4.5	2.1
Current Liabilities from Risk Management Activities	0.6	0.1
Utility Segments | Non-hedge derivatives | Petroleum product contracts
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	0	0.2
Current Liabilities from Risk Management Activities	0.1	0
Utility Segments | Non-hedge derivatives | Coal Contract [Member]
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	0	0.3
Long-term Assets from Risk Management Activities	0	2.2
Current Liabilities from Risk Management Activities	2.0	4.7
Long-term Liabilities from Risk Management Activities	0.3	4.3
Utility Segments | Cash flow hedges | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current assets from risk management activities		0
Current Liabilities from Risk Management Activities		0.4
Nonregulated Segments | Non-hedge derivatives | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	61.3	51.7
Long-term Assets from Risk Management Activities	29.1	11.5
Current Liabilities from Risk Management Activities	52.1	48.5
Long-term Liabilities from Risk Management Activities	18.2	7.6
Nonregulated Segments | Non-hedge derivatives | Electric contracts
Derivative assets and liabilities from risk management activities
Current assets from risk management activities	114.0	88.6
Long-term Assets from Risk Management Activities	32.4	30.7
Current Liabilities from Risk Management Activities	136.5	114.2
Long-term Liabilities from Risk Management Activities	$ 45.1	$ 45.7