Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Revision of Prior Period Accounting Standards Update Adjustment [Member]	Common Stock [Member]	Additional Paid in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings (Loss) [Member]	Retained Earnings (Loss) [Member] Revision of Prior Period Accounting Standards Update Adjustment [Member]	Total Company Stockholders' Equity [Member]	Total Company Stockholders' Equity [Member] Revision of Prior Period Accounting Standards Update Adjustment [Member]	Noncontrolling Interests [Member]
Beginning Balance at Dec. 31, 2017	$ 14,160	$ 3	$ 4	$ 8,234	$ (1,110)	$ 6,966	$ 3	$ 14,094	$ 3	$ 66
Begining Balance, shares at Dec. 31, 2017			380
Net income (loss)	(22)					(31)		(31)		9
Other comprehensive income (loss), net	(327)				(327)			(327)
Cash dividends, per common share	$ (76)					$ (76)		$ (76)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201802Member					us-gaap:AccountingStandardsUpdate201802Member		us-gaap:AccountingStandardsUpdate201802Member
Noncontrolling interest	$ (5)									(5)
Stock-based compensation	110			110				$ 110
Common stock issued	54			54				54
Common stock issued, shares			3
Withholding taxes	(8)			(8)				(8)
Ending Balance at Dec. 31, 2018	13,889		$ 4	8,390	(1,437)	$ 6,862		13,819		70
Ending Balance, shares at Dec. 31, 2018			383
Net income (loss)	(6,093)					(6,095)		(6,095)		2
Other comprehensive income (loss), net	14				14			14
Cash dividends, per common share	$ (77)					$ (77)		$ (77)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201802Member					us-gaap:AccountingStandardsUpdate201802Member		us-gaap:AccountingStandardsUpdate201802Member
Noncontrolling interest	$ (4)									(4)
Stock-based compensation	130			130				$ 130
Common stock issued	7			7				7
Common stock issued, shares			3
Withholding taxes	(20)			(20)				(20)
Ending Balance at Dec. 31, 2019	7,846	$ (5)	$ 4	8,507	(1,423)	$ 690	$ (5)	7,778	$ (5)	68
Ending Balance, shares at Dec. 31, 2019			386
Net income (loss)	(2,537)					(2,542)		(2,542)		5
Other comprehensive income (loss), net	(86)				(86)			(86)
Cash dividends, per common share	$ (19)					$ (19)		$ (19)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201802Member					us-gaap:AccountingStandardsUpdate201802Member		us-gaap:AccountingStandardsUpdate201802Member
Noncontrolling interest	$ (4)									(4)
Stock-based compensation	104			104				$ 104
Common stock issued, shares			2
Withholding taxes	(20)			(20)				(20)
Ending Balance at Dec. 31, 2020	$ 5,279		$ 4	$ 8,591	$ (1,509)	$ (1,876)		$ 5,210		$ 69
Ending Balance, shares at Dec. 31, 2020			388