FAIR VALUE (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Assets
Risk Management Asset	$ 2.9	$ 3.9
Liabilities
Risk Management Liability	3.3	9.7
Fair Value, Assets and Liabilities Transfers Between the Levels of the Fair Value Hierarchy
Fair Value Transfers, Amount	0		0
Fair value measurements on a recurring basis | Level 1
Assets
Risk Management Asset	0.2	0.2
Liabilities
Risk Management Liability	0.4	0.6
Fair value measurements on a recurring basis | Level 1 | Natural gas contracts
Assets
Risk Management Asset	0.2	0.1
Liabilities
Risk Management Liability	0.3	0.6
Fair value measurements on a recurring basis | Level 1 | FTRs
Assets
Risk Management Asset	0	0
Liabilities
Risk Management Liability	0	0
Fair value measurements on a recurring basis | Level 1 | Petroleum product contracts
Assets
Risk Management Asset		0.1
Liabilities
Risk Management Liability	0.1
Fair value measurements on a recurring basis | Level 1 | Coal contract
Assets
Risk Management Asset		0
Liabilities
Risk Management Liability	0	0
Fair value measurements on a recurring basis | Level 2
Assets
Risk Management Asset	0	0
Liabilities
Risk Management Liability	0	0
Fair value measurements on a recurring basis | Level 2 | Natural gas contracts
Assets
Risk Management Asset	0	0
Liabilities
Risk Management Liability	0	0
Fair value measurements on a recurring basis | Level 2 | FTRs
Assets
Risk Management Asset	0	0
Liabilities
Risk Management Liability	0	0
Fair value measurements on a recurring basis | Level 2 | Petroleum product contracts
Assets
Risk Management Asset		0
Liabilities
Risk Management Liability	0
Fair value measurements on a recurring basis | Level 2 | Coal contract
Assets
Risk Management Asset		0
Liabilities
Risk Management Liability	0	0
Fair value measurements on a recurring basis | Level 3
Assets
Risk Management Asset	2.7	3.7
Liabilities
Risk Management Liability	2.9	9.1
Fair value measurements on a recurring basis | Level 3 | Natural gas contracts
Assets
Risk Management Asset	0	0
Liabilities
Risk Management Liability	0	0
Fair value measurements on a recurring basis | Level 3 | FTRs
Assets
Risk Management Asset	2.7	1.2
Liabilities
Risk Management Liability	0.6	0.1
Fair value measurements on a recurring basis | Level 3 | Petroleum product contracts
Assets
Risk Management Asset		0
Liabilities
Risk Management Liability	0
Fair value measurements on a recurring basis | Level 3 | Coal contract
Assets
Risk Management Asset	0	2.5
Liabilities
Risk Management Liability	2.3	9.0
Fair value measurements on a recurring basis | Total
Assets
Risk Management Asset	2.9	3.9
Liabilities
Risk Management Liability	3.3	9.7
Fair value measurements on a recurring basis | Total | Natural gas contracts
Assets
Risk Management Asset	0.2	0.1
Liabilities
Risk Management Liability	0.3	0.6
Fair value measurements on a recurring basis | Total | FTRs
Assets
Risk Management Asset	2.7	1.2
Liabilities
Risk Management Liability	0.6	0.1
Fair value measurements on a recurring basis | Total | Petroleum product contracts
Assets
Risk Management Asset		0.1
Liabilities
Risk Management Liability	0.1
Fair value measurements on a recurring basis | Total | Coal contract
Assets
Risk Management Asset		2.5
Liabilities
Risk Management Liability	$ 2.3	$ 9.0