RISK MANAGEMENT ACTIVITIES (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets
Gross Amount	$ 232.5	$ 188.2
Derivative assets not subject to master netting or similar arrangements	0.3	2.5
Total risk management assets, Gross Amount	232.8	190.7
Gross Amount Not Offset in the Balance Sheet, including Cash Collateral	163.7	148.4
Net Amount	68.8	39.8
Total risk management assets, Net Amount	69.1	42.3
Liabilities
Gross Amount	185.3	230.7
Derivative liabilities not subject to master netting or similar arrangements	4.9	9.6
Total risk management liabilities, Gross Amount	190.2	240.3
Gross Amount Not Offset in the Balance Sheet, including Cash Collateral	163.7	163.6
Net Amount	21.6	67.1
Total risk management liabilities, Net Amount	26.5	76.7
Utility Segments
Assets
Gross Amount	12.8	5.7
Gross Amount Not Offset in the Balance Sheet, including Cash Collateral	3.4	3.0
Net Amount	9.4	2.7
Liabilities
Gross Amount	3.9	15.3
Gross Amount Not Offset in the Balance Sheet, including Cash Collateral	3.4	3.8
Net Amount	0.5	11.5
Nonregulated Segments
Assets
Gross Amount	219.7	182.5
Gross Amount Not Offset in the Balance Sheet, including Cash Collateral	160.3	145.4
Net Amount	59.4	37.1
Liabilities
Gross Amount	181.4	215.4
Gross Amount Not Offset in the Balance Sheet, including Cash Collateral	160.3	159.8
Net Amount	$ 21.1	$ 55.6