EARNINGS PER SHARE - Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Basic EPS calculation
Net income (loss) attributable to common stock	$ 53	$ (50)
Less: net income (loss) allocated to participating securities	(1)
Net income (loss) available to common stockholders	$ 52	$ (50)
Weighed-average common shares outstanding - basic	42.3	38.5
Basic EPS (in dollars per share)	$ 1.23	$ (1.30)
Diluted EPS calculation
Net income (loss) attributable to common stock	$ 53	$ (50)
Less: net income (loss) allocated to participating securities	(1)
Net income (loss) available to common stockholders	$ 52	$ (50)
Weighed-average common shares outstanding - basic	42.3	38.5
Dilutive effect of potentially dilutive securities	0.3
Weighted-average common shares outstanding - diluted	42.6	38.5
Diluted EPS (in dollars per share)	$ 1.22	$ (1.30)