Condensed Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock Outstanding	Treasury Shares at Cost	Par Value and Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance, beginning of period at Dec. 31, 2017	$ 22,559		$ (4)	$ 38,629	$ 8	$ (16,074)
Common stock, shares outstanding, beginning (in shares) at Dec. 31, 2017		859,406,651
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,248					2,248
Other comprehensive (loss) income	0
Stock-based compensation	361			361
Exercise of stock options	3			3
Exercise of stock options (in shares)		174,514
Stock issued for employee stock purchase plan	103			103
Stock issued for employee stock purchase plan (in shares)		2,011,970
Issuance of vested restricted stock units (in shares)		4,707,512
Issuance of restricted stock awards (in shares)		354,459
Shares withheld related to net share settlement of stock awards and stock options	(89)			(89)
Shares withheld related to net share settlement of stock awards and stock options (in shares)		(1,481,129)
Repurchases of common stock	(1,054)			(1,054)
Repurchases of common stock (in shares)		(16,738,758)
Transfer RSU from NQDC plan			(3)	3
Transfer RSU to NQDC plan (in shares)		(54,540)
Prior year retained earnings	224				(8)	232
Balance, end of period at Sep. 30, 2018	24,355		(7)	37,956	0	(13,594)
Common stock, shares outstanding, ending (in shares) at Sep. 30, 2018		848,380,679
Balance, beginning of period at Jun. 30, 2018	23,390		(7)	37,786	0	(14,389)
Common stock, shares outstanding, beginning (in shares) at Jun. 30, 2018		847,225,746
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	795					795
Other comprehensive (loss) income	0
Stock-based compensation	127			127
Exercise of stock options	0			0
Exercise of stock options (in shares)		36,973
Stock issued for employee stock purchase plan	48			48
Stock issued for employee stock purchase plan (in shares)		942,475
Issuance of vested restricted stock units (in shares)		251,953
Shares withheld related to net share settlement of stock awards and stock options	$ (5)			(5)
Shares withheld related to net share settlement of stock awards and stock options (in shares)		(77,323)
Distribution from NQDC plan (in shares)	855
Balance, end of period at Sep. 30, 2018	$ 24,355		(7)	37,956	0	(13,594)
Common stock, shares outstanding, ending (in shares) at Sep. 30, 2018		848,380,679
Balance, beginning of period at Dec. 31, 2018	$ 24,718		(6)	38,010	(332)	(12,954)
Common stock, shares outstanding, beginning (in shares) at Dec. 31, 2018	850,180,317	850,180,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 2,717					2,717
Other comprehensive (loss) income	(738)				(738)
Stock-based compensation	404			404
Exercise of stock options	1			1
Exercise of stock options (in shares)		70,754
Stock issued for employee stock purchase plan	124			124
Stock issued for employee stock purchase plan (in shares)		2,091,650
Issuance of vested restricted stock units (in shares)		4,729,270
Forfeiture of restricted stock awards (in shares)		(20,769)
Shares withheld related to net share settlement of stock awards and stock options	(108)			(108)
Shares withheld related to net share settlement of stock awards and stock options (in shares)		(1,474,011)
Transfer RSU from NQDC plan			(2)	2
Transfer RSU to NQDC plan (in shares)		(19,540)
Prior year retained earnings	653					653
Balance, end of period at Sep. 30, 2019	$ 27,771		(8)	38,433	(1,070)	(9,584)
Common stock, shares outstanding, ending (in shares) at Sep. 30, 2019	855,557,671	855,557,671
Balance, beginning of period at Jun. 30, 2019	$ 26,967		(8)	38,242	(813)	(10,454)
Common stock, shares outstanding, beginning (in shares) at Jun. 30, 2019		854,452,642
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	870					870
Other comprehensive (loss) income	(257)				(257)
Stock-based compensation	140			140
Exercise of stock options (in shares)		19,619
Stock issued for employee stock purchase plan	55			55
Stock issued for employee stock purchase plan (in shares)		955,849
Issuance of vested restricted stock units (in shares)		179,155
Shares withheld related to net share settlement of stock awards and stock options	(4)			(4)
Shares withheld related to net share settlement of stock awards and stock options (in shares)		(53,349)
Distribution from NQDC plan (in shares)		3,755
Balance, end of period at Sep. 30, 2019	$ 27,771		$ (8)	$ 38,433	$ (1,070)	$ (9,584)
Common stock, shares outstanding, ending (in shares) at Sep. 30, 2019	855,557,671	855,557,671