RISK MANAGEMENT ACTIVITIES (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets
Derivative assets subject to master netting or similar arrangements, gross amount	$ 211.3	$ 188.2
Potential Effects of Netting, Including Cash Collateral	121.5	148.4
Derivative assets subject to master netting or similar arrangements, net amount	89.8	39.8
Derivative assets not subject to master netting or similar arrangements	1.7	2.5
Risk Management Assets	213.0	190.7
Total Risk Management Assets, Net Amount	91.5	42.3
Liabilities
Derivative liabilities subject to master netting or similar arrangements, gross amount	213.7	230.7
Potential Effects of Netting, Including Cash Collateral	147.9	163.6
Derivative liabilities subject to master netting or similar arrangements, net amount	65.8	67.1
Derivative liabilities not subject to master netting or similar arrangement	3.4	9.6
Risk Management Liabilities	217.1	240.3
Total Risk Management Liabilities, Net Amount	69.2	76.7
Nonregulated Segments
Assets
Derivative assets subject to master netting or similar arrangements, gross amount	205.4	182.5
Potential Effects of Netting, Including Cash Collateral	119.2	145.4
Derivative assets subject to master netting or similar arrangements, net amount	86.2	37.1
Liabilities
Derivative liabilities subject to master netting or similar arrangements, gross amount	207.1	215.4
Potential Effects of Netting, Including Cash Collateral	145.2	159.8
Derivative liabilities subject to master netting or similar arrangements, net amount	61.9	55.6
Utility Segments
Assets
Derivative assets subject to master netting or similar arrangements, gross amount	5.9	5.7
Potential Effects of Netting, Including Cash Collateral	2.3	3.0
Derivative assets subject to master netting or similar arrangements, net amount	3.6	2.7
Liabilities
Derivative liabilities subject to master netting or similar arrangements, gross amount	6.6	15.3
Potential Effects of Netting, Including Cash Collateral	2.7	3.8
Derivative liabilities subject to master netting or similar arrangements, net amount	$ 3.9	$ 11.5