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	1,453					1,453
Other comprehensive loss	0
Stock-based compensation	234			234
Exercise of stock options	3			3
Exercise of stock options (in shares)		137,541
Stock issued for employee stock purchase plan	55			55
Stock issued for employee stock purchase plan (in shares)		1,069,495
Issuance of vested restricted stock units (in shares)		4,455,559
Issuance of restricted stock awards (in shares)		354,459
Shares withheld related to net share settlement of stock awards and stock options	(84)			(84)
Shares withheld related to net share settlement of stock awards and stock options (in shares)		(1,403,806)
Repurchases of common stock	(1,054)			(1,054)
Repurchases of common stock (in shares)		(16,738,758)
Transfer RSU to NQDC plan			(3)	3
Transfer RSU to NQDC plan (in shares)		(55,395)
Prior year retained earnings	224				(8)	232
Balance, end of period at Jun. 30, 2018	23,390		(7)	37,786	0	(14,389)
Common stock, shares outstanding, ending (in shares) at Jun. 30, 2018		847,225,746
Balance, beginning of period at Mar. 31, 2018	22,876		(7)	38,057	5	(15,179)
Common stock, shares outstanding, beginning (in shares) at Mar. 31, 2018		853,066,229
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	782					782
Other comprehensive loss	3				3
Stock-based compensation	126			126
Exercise of stock options	1			1
Exercise of stock options (in shares)		59,106
Stock issued for employee stock purchase plan (in shares)		(17)
Issuance of vested restricted stock units (in shares)		508,554
Shares withheld related to net share settlement of stock awards and stock options	(10)			(10)
Shares withheld related to net share settlement of stock awards and stock options (in shares)		(167,907)
Repurchases of common stock	(388)			(388)
Repurchases of common stock (in shares)		(6,240,219)
Prior year retained earnings					(8)	8
Balance, end of period at Jun. 30, 2018	23,390		(7)	37,786	0	(14,389)
Common stock, shares outstanding, ending (in shares) at Jun. 30, 2018		847,225,746
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	$ 1,847					1,847
Other comprehensive loss	(481)				(481)
Stock-based compensation	264			264
Exercise of stock options	1			1
Exercise of stock options (in shares)		51,135
Stock issued for employee stock purchase plan	69			69
Stock issued for employee stock purchase plan (in shares)		1,135,801
Issuance of vested restricted stock units (in shares)		4,550,115
Forfeiture of restricted stock awards (in shares)		(20,769)
Shares withheld related to net share settlement of stock awards and stock options	(104)			(104)
Shares withheld related to net share settlement of stock awards and stock options (in shares)		(1,420,662)
Transfer RSU to NQDC plan			(2)	2
Transfer RSU to NQDC plan (in shares)		(23,295)
Prior year retained earnings	653					653
Balance, end of period at Jun. 30, 2019	$ 26,967		(8)	38,242	(813)	(10,454)
Common stock, shares outstanding, ending (in shares) at Jun. 30, 2019	854,452,642	854,452,642
Balance, beginning of period at Mar. 31, 2019	$ 26,181		(5)	38,100	(521)	(11,393)
Common stock, shares outstanding, beginning (in shares) at Mar. 31, 2019		854,380,118
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	939					939
Other comprehensive loss	(292)				(292)
Stock-based compensation	143			143
Exercise of stock options (in shares)		19,261
Stock issued for employee stock purchase plan (in shares)		(36,710)
Issuance of vested restricted stock units (in shares)		206,143
Forfeiture of restricted stock awards (in shares)		(20,769)
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)		(56,041)
Transfer RSU to NQDC plan			(3)	3
Transfer RSU to NQDC plan (in shares)		(39,360)
Balance, end of period at Jun. 30, 2019	$ 26,967		$ (8)	$ 38,242	$ (813)	$ (10,454)
Common stock, shares outstanding, ending (in shares) at Jun. 30, 2019	854,452,642	854,452,642