CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Deficit	Retained Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Stockholders' Equity Attributable to Parent	Stockholders' Equity Attributable to Parent Cumulative Effect, Period of Adoption, Adjustment	Non- controlling Interest
Beginning balance at Dec. 31, 2017	$ 14,181	$ (18)	$ 508	$ (574)	$ 10,362	$ 4,611	$ 45	$ (763)	$ (63)	$ 14,144	$ (18)	$ 37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(7,029)					(6,942)		(83)		(7,025)		(4)
Dividends declared on common stock	(436)				(211)	(225)				(436)
Equity compensation, net of tax	64		1	(11)	74					64
Common stock purchased and retired	(1,507)		(63)		(1,444)					(1,507)
Portion of net income (loss) attributable to noncontrolling interests	(2)							(4)		(4)		2
Ending balance at Dec. 31, 2018	5,253		446	(585)	8,781	(2,511)		(913)		5,218		35
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	100					107		(6)		101		(1)
Dividends declared on common stock	(393)				(393)					(393)
Equity compensation, net of tax	38		1	(5)	42					38
Portion of net income (loss) attributable to noncontrolling interests	1							(1)		(1)		2
Distributions to noncontrolling interests	(3)											(3)
Ending balance at Dec. 31, 2019	4,996		447	(590)	8,430	(2,404)		(920)		4,963		33
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	(730)					(770)		45		(725)		(5)
Dividends declared on common stock	(392)				(392)					(392)
Equity compensation, net of tax	33		1	(8)	40					33
Portion of net income (loss) attributable to noncontrolling interests	(4)							(5)		(5)		1
Distributions to noncontrolling interests	(3)											(3)
Ending balance at Dec. 31, 2020	$ 3,900		$ 448	$ (598)	$ 8,078	$ (3,174)		$ (880)		$ 3,874		$ 26