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				93
Beginning Balance at Dec. 31, 2015	$ 18,553	$ 0	$ 770	$ (3,554)	$ 6,498	$ 14,974	$ (135)
Shares Beginning Balance at Dec. 31, 2015			770
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued - stock based compensation	42			128	(86)
Shares repurchased	(5)			$ (5)
Stock-based compensation	(35)				(35)
Net loss	2,140					2,140
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	52						52
Dividends paid	(162)					(162)
Common stock issuance	1,236		$ 167
Stockholders' Equity Note, Spinoff Transaction					1,069
Shares issued - stock based compensation				(3)
Shares repurchased				0
Stock Issued During Period, Shares, New Issues			167
Ending Balance at Dec. 31, 2016	17,541	0	$ 937	$ (3,431)	7,446	12,672	(83)
Shares Ending Balance at Dec. 31, 2016			937
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares				90
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)
Common stock issuance	0		$ 0		0
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			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	0			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