FAIR VALUE (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes in the fair value of items measured on a recurring basis and categorized as Level 3 measurements
Balance at the beginning of period	$ (5.4)	$ (5.7)	$ 4.5
Net realized gains (losses) included in earnings	3.0	1.8	(1.2)
Net unrealized gains (losses) recorded as regulatory assets or liabilities	0.3	5.7	(9.2)
Purchases	3.2	2.8	2.8
Sales	(0.2)	(0.1)	(0.1)
Settlements	(2.2)	(9.9)	(2.5)
Balance at the end of period	(1.3)	(5.4)	(5.7)
Unrealized gain (loss) recognized in income
Impact on earnings of unrealized gains (losses) on level 3 derivatives	0	0	0
FTRs
Changes in the fair value of items measured on a recurring basis and categorized as Level 3 measurements
Balance at the beginning of period	1.1	1.2	2.0
Net realized gains (losses) included in earnings	3.0	1.8	(1.2)
Net unrealized gains (losses) recorded as regulatory assets or liabilities	(0.1)	(0.1)	(1.2)
Purchases	3.2	2.8	2.8
Sales	(0.2)	(0.1)	(0.1)
Settlements	(5.8)	(4.5)	(1.1)
Balance at the end of period	1.2	1.1	1.2
Coal contract
Changes in the fair value of items measured on a recurring basis and categorized as Level 3 measurements
Balance at the beginning of period	(6.5)	(6.9)	2.5
Net realized gains (losses) included in earnings	0	0	0
Net unrealized gains (losses) recorded as regulatory assets or liabilities	0.4	5.8	(8.0)
Purchases	0	0	0
Sales	0	0	0
Settlements	3.6	(5.4)	(1.4)
Balance at the end of period	$ (2.5)	$ (6.5)	$ (6.9)