EARNINGS PER SHARE - Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic EPS calculation
Net (loss) income	$ (132)	$ 546	$ (127)	$ 356
Net income attributable to noncontrolling interest	(1)		(1)
NET (LOSS) INCOME ATTRIBUTABLE TO COMMON STOCK	(133)	546	(128)	356
Less: net income (loss) allocated to participating securities	0	(14)	0	(7)
Net (loss) income available to common stockholders	$ (133)	$ 532	$ (128)	$ 349
Weighed-average common shares outstanding - basic	42.7	40.8	42.5	39.7
Basic EPS (in dollars per share)	$ (3.11)	$ 13.04	$ (3.01)	$ 8.79
Diluted EPS calculation
Net (loss) income	$ (132)	$ 546	$ (127)	$ 356
Net income attributable to noncontrolling interest	(1)		(1)
Net (loss) income attributable to common stock	(133)	546	(128)	356
Less: net income (loss) allocated to participating securities	0	(14)	0	(7)
Net (loss) income available to common stockholders	$ (133)	$ 532	$ (128)	$ 349
Weighed-average common shares outstanding - basic	42.7	40.8	42.5	39.7
Dilutive effect of potentially dilutive securities	0.0	0.0	0.0	0.0
Weighted-average common shares outstanding - diluted	42.7	40.8	42.5	39.7
Diluted EPS (in dollars per share)	$ (3.11)	$ 13.04	$ (3.01)	$ 8.79
Previously reported
Basic EPS calculation
Basic EPS (in dollars per share)		13.45		$ 8.97
Diluted EPS calculation
Diluted EPS (in dollars per share)		$ 13.06
Percentage of change in basic earnings per share		3.00%		2.00%