CAPITAL STOCK - Net Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic:
Net loss attributable to common stock	$ (2,976)	$ (170)	$ (360)	$ (47)	$ (381)	$ 81	$ 195	$ 145	$ (3,553)	$ 40	$ 1,304
Weighted average number of shares outstanding, basic (in shares)									377	382	381
Basic net income (loss) per share (in USD per share)	$ (7.89)	$ (0.45)	$ (0.96)	$ (0.12)	$ (1.00)	$ 0.21	$ 0.51	$ 0.38	$ (9.43)	$ 0.11	$ 3.42
Effect of Dilutive Securities:
Stock options and other, shares (in shares)									0	2	2
Stock options and other, per share (in USD per share)									$ 0	$ 0	$ (0.01)
Diluted:
Income (loss) attributable to common stock									$ (3,553)	$ 40	$ 1,304
Weighted average number of shares outstanding, diluted (in shares)									377	384	383
Diluted net income (loss) per share (in USD per share)	$ (7.89)	$ (0.45)	$ (0.96)	$ (0.12)	$ (1.00)	$ 0.21	$ 0.51	$ 0.38	$ (9.43)	$ 0.11	$ 3.41