Condensed Consolidated Statements of Stockholders' Equity Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (59)
Beginning Balance at Dec. 31, 2017		$ 16	$ (1,717)	$ 17,161	$ (8,390)	$ (59)
Beginning Balance (Shares) at Dec. 31, 2017		1,621,062,898
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	298
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment	10					10
Derivative financial instruments	(80)					(80)
Defined benefit pensions and other items	0
Impact of stock-based compensation plans, net of tax (Shares)		6,125,111
Impact of stock-based compensation plans, net of tax				23
Ending Balance at Mar. 31, 2018		$ 16	(1,717)	17,184	(8,326)	(128)
Ending Balance (Shares) at Mar. 31, 2018		1,627,188,009
Accumulated Other Comprehensive Income (Loss), Net of Tax	(128)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Adjustments for New Accounting Pronouncement [Member]					(233)
Accumulated Other Comprehensive Income (Loss), Net of Tax	33
Beginning Balance at Dec. 31, 2018	$ 8,726	$ 16	(1,717)	17,346	(6,953)	33
Beginning Balance (Shares) at Dec. 31, 2018	1,632,148,030	1,632,148,030
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 424				424
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment	6					6
Derivative financial instruments	49					49
Defined benefit pensions and other items	1					(1)
Impact of stock-based compensation plans, net of tax (Shares)		6,001,343
Impact of stock-based compensation plans, net of tax				28
Ending Balance at Mar. 31, 2019	$ 9,233	$ 16	$ (1,717)	$ 17,374	$ (6,528)	$ 87
Ending Balance (Shares) at Mar. 31, 2019	1,638,149,373	1,638,149,373
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 87