GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended			9 Months Ended		1 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Depreciation and amortization	Sep. 30, 2013 Depreciation and amortization	Sep. 30, 2014 Depreciation and amortization	Sep. 30, 2013 Depreciation and amortization	Sep. 30, 2014 Regulatory assets	Sep. 30, 2014 Contractual service agreements	Dec. 31, 2013 Contractual service agreements	Oct. 31, 2014 Contractual service agreements Subsequent event
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying amount of goodwill	$ 0	$ 0
Goodwill impairment loss	0
Contractual service agreements
Contractual service agreements, gross carrying amount								15.6	15.6
Contractual service agreements, accumulated amortization								(3.5)	(1.8)
Contractual service agreements, net carrying amount								12.1	13.8
Contractual service agreements with shortened amortization period										1
Weighted-average amortization period								4 years
Recovery period								7 years
Amortization expense			0.5	0.6	1.7	1.2
Amortization expense for the next five years
Future amortization expense period	5 years
Amortization expense, 2014			2.2		2.2		0.3
Amortization expense, 2015			2.2		2.2		1.0
Amortization expense, 2016			2.2		2.2		1.0
Amortization expense, 2017			1.7		1.7		0.5
Amortization expense, 2018			$ 1.2		$ 1.2		$ 0