RISK MANAGEMENT ACTIVITIES (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities	$ 227.2	$ 236.9
Long-term Assets from Risk Management Activities	64.4	89.4
Current Liabilities from Risk Management Activities	311.6	289.6
Long-term Liabilities from Risk Management Activities	102.0	99.7
Risk Management Assets	291.6	326.3
Risk Management Liabilities	413.6	389.3
Cash collateral provided to others	50.9	33.3
Cash collateral received from others	2.3	4.5
Utility Segments | Cash flow hedges | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current Liabilities from Risk Management Activities	0.9	1.0
Long-term Liabilities from Risk Management Activities	0.2
Utility Segments | Non-hedge derivatives | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities	9.1	2.2
Long-term Assets from Risk Management Activities	0.1	1.6
Current Liabilities from Risk Management Activities	35.4	23.6
Long-term Liabilities from Risk Management Activities	8.2	1.4
Utility Segments | Non-hedge derivatives | FTRs
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities	2.3	3.1
Current Liabilities from Risk Management Activities	0.1	0.2
Utility Segments | Non-hedge derivatives | Petroleum product services
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities	0.1	0.6
Utility Segments | Non-hedge derivatives | Coal contract
Derivative assets and liabilities from risk management activities
Long-term Assets from Risk Management Activities		3.7
Current Liabilities from Risk Management Activities	2.5	1.2
Long-term Liabilities from Risk Management Activities	4.4
Nonregulated Segments | Cash flow hedges | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities		1.6
Long-term Assets from Risk Management Activities		0.1
Current Liabilities from Risk Management Activities		9.2
Long-term Liabilities from Risk Management Activities		0.9
Nonregulated Segments | Cash flow hedges | Electric contracts
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities		9.6
Long-term Assets from Risk Management Activities		4.9
Current Liabilities from Risk Management Activities		17.4
Long-term Liabilities from Risk Management Activities		9.1
Nonregulated Segments | Fair value hedges | Interest rate swaps
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities		0.9
Nonregulated Segments | Non-hedge derivatives | Natural gas contracts
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities	121.6	132.0
Long-term Assets from Risk Management Activities	41.9	62.3
Current Liabilities from Risk Management Activities	120.5	113.8
Long-term Liabilities from Risk Management Activities	40.5	57.7
Nonregulated Segments | Non-hedge derivatives | Electric contracts
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities	93.9	85.7
Long-term Assets from Risk Management Activities	22.4	16.5
Current Liabilities from Risk Management Activities	152.0	122.0
Long-term Liabilities from Risk Management Activities	48.7	30.3
Nonregulated Segments | Non-hedge derivatives | Foreign exchange contracts
Derivative assets and liabilities from risk management activities
Current Assets from Risk Management Activities	0.2	1.2
Long-term Assets from Risk Management Activities		0.3
Current Liabilities from Risk Management Activities	0.2	1.2
Long-term Liabilities from Risk Management Activities		$ 0.3