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]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Adjustments for New Accounting Pronouncement [Member]					$ (233)
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
Total other comprehensive income (loss)						(69)
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
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)	$ 853
Total other comprehensive income (loss)	42
Ending Balance at Jun. 30, 2018		$ 16	(1,717)	17,231	(7,770)	(16)
Ending Balance (Shares) at Jun. 30, 2018		1,628,876,252
Beginning Balance at Mar. 31, 2018		$ 16	(1,717)	17,184	(8,326)	(128)
Beginning Balance (Shares) at Mar. 31, 2018		1,627,188,009
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	555				555
Total other comprehensive income (loss)	112					112
Impact of stock-based compensation plans, net of tax (Shares)		1,688,243
Impact of stock-based compensation plans, net of tax				47
Ending Balance at Jun. 30, 2018		$ 16	(1,717)	17,231	(7,770)	(16)
Ending Balance (Shares) at Jun. 30, 2018		1,628,876,252
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)					432
Total other comprehensive income (loss)						40
Impact of stock-based compensation plans, net of tax (Shares)		2,395,031
Impact of stock-based compensation plans, net of tax				73
Ending Balance at Sep. 30, 2018		$ 16	(1,717)	17,304	(7,339)	25
Ending Balance (Shares) at Sep. 30, 2018		1,631,271,283
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)					386
Total other comprehensive income (loss)						8
Impact of stock-based compensation plans, net of tax (Shares)		876,747
Impact of stock-based compensation plans, net of tax				42
Ending Balance at Dec. 31, 2018	$ 8,726	$ 16	(1,717)	17,346	(6,953)	33
Ending 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
Total other comprehensive income (loss)						54
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		$ 16	(1,717)	17,374	(6,528)	87
Ending Balance (Shares) at Mar. 31, 2019		1,638,149,373
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)	$ 578
Total other comprehensive income (loss)	45
Ending Balance at Jun. 30, 2019	$ 9,425	$ 16	(1,717)	17,422	(6,375)	78
Ending Balance (Shares) at Jun. 30, 2019	1,639,098,930	1,639,098,930
Beginning Balance at Mar. 31, 2019		$ 16	(1,717)	17,374	(6,528)	87
Beginning Balance (Shares) at Mar. 31, 2019		1,638,149,373
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 154				154
Total other comprehensive income (loss)	(9)					(9)
Impact of stock-based compensation plans, net of tax (Shares)		949,557
Impact of stock-based compensation plans, net of tax				48
Ending Balance at Jun. 30, 2019	$ 9,425	$ 16	$ (1,717)	$ 17,422	$ (6,375)	$ 78
Ending Balance (Shares) at Jun. 30, 2019	1,639,098,930	1,639,098,930