Consolidated Statements of Stockholders Equity - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Securities Exchangeable for 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					73
Beginning Balance at Dec. 31, 2013	$ 19,344	$ 0	$ 770	$ 0	$ (2,903)	$ 6,592	$ 15,135	$ (250)
Shares Beginning Balance at Dec. 31, 2013			770
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued - stock based compensation	219				276	(57)
Shares repurchased	(1,015)				$ (1,015)
Stock-based compensation	(4)					(4)
Net income	3,046						3,046
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	(27)							(27)
Dividends paid	(543)						(543)
Shares issued - stock based compensation					(7)
Shares repurchased					29
Ending Balance at Dec. 31, 2014	21,020	0	$ 770	0	$ (3,642)	6,531	17,638	(277)
Shares Ending Balance at Dec. 31, 2014			770
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares					95
Shares issued - stock based compensation	64				$ 96	(32)
Shares repurchased	(8)				$ (8)
Stock-based compensation	(1)					(1)
Net income	(2,204)						(2,204)
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	142							142
Dividends paid	(460)						(460)
Shares issued - stock based compensation					(2)
Shares repurchased					0
Ending Balance at Dec. 31, 2015	$ 18,553	0	$ 770	0	$ (3,554)	6,498	14,974	(135)
Shares Ending Balance at Dec. 31, 2015			770
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares	93				93
Stock Issued During Period, Value, New Issues			$ 167
Shares issued - stock based compensation	$ 42				$ 128	(86)
Shares repurchased	(5)				$ (5)
Stock-based compensation	(35)					(35)
Net income	(2,140)
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	52							52
Dividends paid	(162)						(162)
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	$ 0	$ (3,431)	7,446	$ 12,672	$ (83)
Shares Ending Balance at Dec. 31, 2016			937
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Note, Spinoff Transaction, Other	$ 1,236					$ 1,069
Treasury shares	90				90