GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Oct. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the carrying amount of goodwill	$ 0	$ 0
Goodwill impairment loss	0
Amortization expense for the next five years
Future amortization expense period	5 years
Regulatory assets
Contractual service agreements
Amortization expense	0.3	0
Amortization expense for the next five years
Amortization expense, 2015	1.0
Amortization expense, 2016	1.0
Amortization expense, 2017	0.5
Amortization expense, 2018	0
Amortization expense, 2019	0
Depreciation and amortization
Contractual service agreements
Amortization expense	2.2	1.8
Amortization expense for the next five years
Amortization expense, 2015	2.2
Amortization expense, 2016	2.2
Amortization expense, 2017	1.7
Amortization expense, 2018	1.2
Amortization expense, 2019	1.2
Contractual service agreements
Contractual service agreements
Contractual service agreements, gross carrying amount	15.6	15.6
Contractual service agreements, accumulated amortization	(4.3)	(1.8)
Contractual service agreements, net carrying amount	$ 11.3	$ 13.8
Contractual service agreements with shortened amortization period			1
Weighted-average amortization period	4 years
Recovery period	7 years