FAIR VALUE (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Assets
Risk Management Asset	$ 4.0		$ 4.0		$ 3.9
Liabilities
Risk Management Liability	3.4		3.4		9.7
Fair Value, Assets and Liabilities Transfers Between the Levels of the Fair Value Hierarchy
Fair Value Transfers, Amount	0	0	0	0
Fair value measurements on a recurring basis | Level 1
Assets
Risk Management Asset	0.3		0.3		0.2
Liabilities
Risk Management Liability	0.3		0.3		0.6
Fair value measurements on a recurring basis | Level 1 | Natural gas contracts
Assets
Risk Management Asset	0.3		0.3		0.1
Liabilities
Risk Management Liability	0.2		0.2		0.6
Fair value measurements on a recurring basis | Level 1 | FTRs
Assets
Risk Management Asset	0		0		0
Liabilities
Risk Management Liability	0		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		0.1
Fair value measurements on a recurring basis | Level 1 | Coal contract
Assets
Risk Management Asset	0		0		0
Liabilities
Risk Management Liability	0		0		0
Fair value measurements on a recurring basis | Level 2
Assets
Risk Management Asset	0		0		0
Liabilities
Risk Management Liability	0		0		0
Fair value measurements on a recurring basis | Level 2 | Natural gas contracts
Assets
Risk Management Asset	0		0		0
Liabilities
Risk Management Liability	0		0		0
Fair value measurements on a recurring basis | Level 2 | FTRs
Assets
Risk Management Asset	0		0		0
Liabilities
Risk Management Liability	0		0		0
Fair value measurements on a recurring basis | Level 2 | Petroleum product contracts
Assets
Risk Management Asset					0
Liabilities
Risk Management Liability	0		0
Fair value measurements on a recurring basis | Level 2 | Coal contract
Assets
Risk Management Asset	0		0		0
Liabilities
Risk Management Liability	0		0		0
Fair value measurements on a recurring basis | Level 3
Assets
Risk Management Asset	3.7		3.7		3.7
Liabilities
Risk Management Liability	3.1		3.1		9.1
Fair value measurements on a recurring basis | Level 3 | Natural gas contracts
Assets
Risk Management Asset	0		0		0
Liabilities
Risk Management Liability	0		0		0
Fair value measurements on a recurring basis | Level 3 | FTRs
Assets
Risk Management Asset	2.2		2.2		1.2
Liabilities
Risk Management Liability	0.4		0.4		0.1
Fair value measurements on a recurring basis | Level 3 | Petroleum product contracts
Assets
Risk Management Asset					0
Liabilities
Risk Management Liability	0		0
Fair value measurements on a recurring basis | Level 3 | Coal contract
Assets
Risk Management Asset	1.5		1.5		2.5
Liabilities
Risk Management Liability	2.7		2.7		9.0
Fair value measurements on a recurring basis | Total
Assets
Risk Management Asset	4.0		4.0		3.9
Liabilities
Risk Management Liability	3.4		3.4		9.7
Fair value measurements on a recurring basis | Total | Natural gas contracts
Assets
Risk Management Asset	0.3		0.3		0.1
Liabilities
Risk Management Liability	0.2		0.2		0.6
Fair value measurements on a recurring basis | Total | FTRs
Assets
Risk Management Asset	2.2		2.2		1.2
Liabilities
Risk Management Liability	0.4		0.4		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		0.1
Fair value measurements on a recurring basis | Total | Coal contract
Assets
Risk Management Asset	1.5		1.5		2.5
Liabilities
Risk Management Liability	$ 2.7		$ 2.7		$ 9.0