GOODWILL AND OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Goodwill and other intangible assets
Changes to the carrying amount of goodwill	$ 0.0	$ 0.0
Goodwill impairment loss	0.0
Intangible assets other than goodwill
Amortized intangible assets, accumulated amortization	(9.1)		$ (7.5)
Unamortized intangible assets, carrying amount	0.4		0.4
Total intangible assets, gross carrying amount	16.0		16.0
Total intangible assets, net carrying amount	6.9		8.5
Contractual service agreements
Intangible assets other than goodwill
Amortized intangible assets, gross carrying amount	15.6		15.6
Amortized intangible assets, accumulated amortization	(9.1)		(7.5)
Amortized intangible assets, net carrying amount	$ 6.5		$ 8.1
Remaining weighted-average amortization period	3 years