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					63
Beginning Balance at Dec. 31, 2012	$ 18,283	$ 0	$ 770	$ 0	$ (2,560)	$ 6,616	$ 13,890	$ (433)
Shares Beginning Balance at Dec. 31, 2012			770
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued - stock based compensation	126				170	(44)
Shares repurchased	(513)				$ (513)
Stock-based compensation	20					20
Net income	1,753						1,753
Other Comprehensive Income (Loss), Net of Tax, Incl Disc Ops	183							183
Dividends paid	(508)						(508)
Shares issued - stock based compensation					(4)
Ending Balance at Dec. 31, 2013	19,344	0	$ 770	0	$ (2,903)	6,592	15,135	(250)
Shares Ending Balance at Dec. 31, 2013			770
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares					73
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				95
Shares issued - stock based compensation	$ 64				$ 96	(32)
Shares repurchased	(8)				$ (8)
Stock-based compensation	(1)					(1)
Net income	(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