Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2014		$ 16	$ (1,717)	$ 16,703	$ (8,689)	$ 144
Balance (Shares) at Dec. 31, 2014		1,575,018,236
Net income (loss)	$ (239)				(239)
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment	(16)					(16)
Net change in derivative financial instruments	(67)					(67)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments and Tax	0
Net change in unrealized costs associated with certain retirement plans	(27)					27
Impact of stock-based compensation plans, net of tax (Shares)		19,195,550
Stock Issued During Period, Value, New Issues		$ 0
Impact of stock-based compensation plans, net of tax				157
Acquisition of treasury stock
Balance (Shares) at Dec. 31, 2015		1,594,213,786
Balance at Dec. 31, 2015		$ 16	(1,717)	16,860	(8,927)	88
Other comprehensive income (loss), net of tax
ProfitLossDueToRounding					1
Net income (loss)	347				347
Foreign currency translation adjustment	(25)					(25)
Net change in derivative financial instruments	(45)					(45)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments and Tax	(6)					(6)
Net change in unrealized costs associated with certain retirement plans	$ 11					(11)
Impact of stock-based compensation plans, net of tax (Shares)		15,457,031
Stock Issued During Period, Value, New Issues		$ 0
Impact of stock-based compensation plans, net of tax				153
Balance (Shares) at Dec. 31, 2016	1,609,670,817	1,609,670,817
Balance at Dec. 31, 2016	$ 6,733	$ 16	(1,717)	17,014	(8,581)	1
Other comprehensive income (loss), net of tax
ProfitLossDueToRounding				1	(1)
Net income (loss)	104				104
Foreign currency translation adjustment	48					48
Net change in derivative financial instruments	(106)					(106)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments and Tax	5					5
Net change in unrealized costs associated with certain retirement plans	$ 6					(6)
Impact of stock-based compensation plans, net of tax (Shares)		11,392,081
Stock Issued During Period, Value, New Issues
Impact of stock-based compensation plans, net of tax				147
Balance (Shares) at Dec. 31, 2017	1,621,062,898	1,621,062,898
Balance at Dec. 31, 2017	$ 7,012	$ 16	$ (1,717)	$ 17,161	$ (8,390)	$ (59)
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 86