CAPITAL STOCK AND EARNINGS PER SHARE - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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 income attributable to common stock	$ (487)	$ 368	$ 349	$ 10	$ 307	$ 157	$ 219	$ 163	$ 240	$ 846	$ 482
Basic weighted average common units outstanding (in shares)									163,493	104,622	97,458
Effect of dilutive securities:
Potential common shares issuable (in shares)									350	307	230
Diluted:
Diluted weighted average common shares outstanding (in shares)									163,843	104,929	97,688
Basic net income attributable to common stock (in dollars per share)	$ (3.04)	$ 2.27	$ 2.12	$ 0.06	$ 2.50	$ 1.59	$ 2.22	$ 1.65	$ 1.47	$ 8.09	$ 4.95
Diluted net income attributable to common stock (in dollars per share)	$ (3.04)	$ 2.26	$ 2.11	$ 0.06	$ 2.50	$ 1.59	$ 2.22	$ 1.65	$ 1.47	$ 8.06	$ 4.94
Antidilutive securities, restricted stock units (in shares)									284	14	46