Consolidated Statements of Stockholders Equity - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares				90
Beginning Balance at Dec. 31, 2016	$ 17,541	$ 0	$ 937	$ (3,431)	$ 7,446	$ 12,672	$ (83)
Shares Beginning Balance at Dec. 31, 2016			937
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued - stock based compensation	67			117	(50)
Shares repurchased	(11)			$ (11)
Stock-based compensation	(17)				(17)
Net loss	5,723					5,723
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	21						21
Dividends paid	(170)					(170)
Shares issued - stock based compensation				(3)
Ending Balance at Dec. 31, 2017	11,708	0	$ 937	$ (3,325)	7,379	6,779	(62)
Shares Ending Balance at Dec. 31, 2017			937
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares				87
Shares issued - stock based compensation	112			$ 221	(109)
Shares repurchased	(712)			$ (712)
Stock-based compensation	(32)				(32)
Net loss	(1,096)					(1,096)
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	125						125
Dividends paid	(169)					(169)
Shares issued - stock based compensation				(6)
Shares repurchased				37
Ending Balance at Dec. 31, 2018	$ 12,128	0	$ 937	$ (3,816)	7,238	7,706	63
Shares Ending Balance at Dec. 31, 2018			937
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares	118			118
Cumulative Effect on Retained Earnings, Net of Tax	$ (31)					(31)
Shares issued - stock based compensation	63			$ 89	(26)
Shares repurchased	(362)			$ (362)
Stock-based compensation	(5)				(5)
Net loss	(480)
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	42						42
Dividends paid	$ (162)					(162)
Shares issued - stock based compensation				(2)
Shares repurchased	0			25
Ending Balance at Dec. 31, 2019	$ 12,153	$ 0	$ 937	$ (4,089)	$ 7,207	$ 7,993	$ 105
Shares Ending Balance at Dec. 31, 2019			937
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares	141			141