CONSOLIDATED STATEMENT OF EQUITY - 6 months ended Jun. 30, 2018 - USD ($) $ in Millions		Total	Subsidiary Equity Transactions [Member]	Equity Component of 7.50% Tangible Equity Units [Member]	Common Stock [Member]	Paid-in Capital [Member]	Paid-in Capital [Member] Subsidiary Equity Transactions [Member]	Paid-in Capital [Member] Equity Component of 7.50% Tangible Equity Units [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member] Subsidiary Equity Transactions [Member]	Noncontrolling Interests [Member] Equity Component of 7.50% Tangible Equity Units [Member]
Balance at Dec. 31, 2017		$ 13,790			$ 57	$ 12,000			$ 1,109	$ (2,132)	$ (338)	$ 3,094
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		191							150			41
Common stock issued		6				6
Share-based compensation expense		84				84
Dividends—common stock		(254)							(254)
Repurchases of common stock		(1,973)								(1,973)
Subsidiary equity transactions			$ 5				$ (14)						$ 19
Settlement of tangible equity units				$ (70)				$ 230						$ (300)
Distributions to noncontrolling interest owners		(238)										(238)
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net		1									1
Balance at Jun. 30, 2018		11,495			$ 57	$ 12,306			1,054	$ (4,105)	(410)	2,593
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change (1)	[1]	$ (47)							$ 49		$ (73)	$ (23)

[1] Beginning January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), and ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. See Note 1—Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements for further information.