CONSOLIDATED STATEMENT OF EQUITY - 3 months ended Mar. 31, 2018 - USD ($) $ in Millions		Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]	Subsidiary Equity Transactions [Member]	Subsidiary Equity Transactions [Member] Paid-in Capital [Member]	Subsidiary Equity Transactions [Member] Noncontrolling Interests [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)		174			121			53
Share-based compensation expense		39		39
Dividends—common stock		(127)			(127)
Repurchases of common stock		(1,959)		(332)		(1,627)
Subsidiary equity transactions									$ 3	$ (6)	$ 9
Distributions to noncontrolling interest owners		(118)						(118)
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net		1					1
Balance at Mar. 31, 2018		11,756	$ 57	$ 11,701	1,152	$ (3,759)	(410)	3,015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change (1)	[1]	$ (47)			$ 49		$ (73)	$ (23)

[1] 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, beginning January 1, 2018; see Note 1—Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements for further information.