EARNINGS PER SHARE - Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic EPS calculation
Net (loss) income attributable to common stock	$ (48)	$ (140)	$ 5	$ (190)
Less: net income (loss) allocated to participating securities	0	0	0	0
Net (loss) income available to common stockholders	$ (48)	$ (140)	$ 5	$ (190)
Weighed-average common shares outstanding - basic	42.4	39.9	42.4	39.2
Basic EPS (in dollars per share)	$ (1.13)	$ (3.51)	$ 0.12	$ (4.85)
Diluted EPS calculation
Net (loss) income attributable to common stock	$ (48)	$ (140)	$ 5	$ (190)
Less: net income (loss) allocated to participating securities	0	0	0	0
Net (loss) income available to common stockholders	$ (48)	$ (140)	$ 5	$ (190)
Weighed-average common shares outstanding - basic	42.4	39.9	42.4	39.2
Dilutive effect of potentially dilutive securities			0.3
Weighted-average common shares outstanding - diluted	42.4	39.9	42.7	39.2
Diluted EPS (in dollars per share)	$ (1.13)	$ (3.51)	$ 0.12	$ (4.85)