UNAUDITED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Millions	Total	Cumulative Effect of Adoption of Accounting Standards Update	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect of Adoption of Accounting Standards Update	Accumulated Other Comprehensive Loss
Balance (in shares) at Dec. 31, 2018			62,949	(17,317)
Balance at Dec. 31, 2018	$ 8,785		$ 0	$ (14,711)	$ 5,445	$ 18,367		$ (316)
Increase (Decrease) in Stockholders' Equity
Net income	3,694					3,694
Foreign currency translation adjustments, net of tax	(63)							(63)
Net unrealized (losses) gains on available-for-sale securities, net of tax	114							114
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)			213
Exercise of stock options and vesting of restricted stock units and performance share units	$ 1		$ 0		1
Repurchase of common stock (in shares)	(3,760)			(3,760)
Repurchase of common stock	$ (6,812)			$ (6,812)
Stock-based compensation and other stock-based payments	232				232
Balance (in shares) at Sep. 30, 2019			63,162	(21,077)
Balance at Sep. 30, 2019	5,951		$ 0	$ (21,523)	5,678	22,061		(265)
Balance (in shares) at Jun. 30, 2019			63,144	(20,378)
Balance at Jun. 30, 2019	5,307		$ 0	$ (20,173)	5,599	20,111		(230)
Increase (Decrease) in Stockholders' Equity
Net income	1,950					1,950
Foreign currency translation adjustments, net of tax	(35)							(35)
Net unrealized (losses) gains on available-for-sale securities, net of tax	0
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)			18
Exercise of stock options and vesting of restricted stock units and performance share units	$ 0		$ 0		0
Repurchase of common stock (in shares)	(699)			(699)
Repurchase of common stock	$ (1,350)			$ (1,350)
Stock-based compensation and other stock-based payments	79				79
Balance (in shares) at Sep. 30, 2019			63,162	(21,077)
Balance at Sep. 30, 2019	5,951		$ 0	$ (21,523)	5,678	22,061		(265)
Balance (in shares) at Dec. 31, 2019			63,179	(21,762)
Balance at Dec. 31, 2019	5,933	$ (3)	$ 0	$ (22,864)	5,756	23,232	$ (3)	(191)
Increase (Decrease) in Stockholders' Equity
Net income	224					224
Foreign currency translation adjustments, net of tax	(3)							(3)
Net unrealized (losses) gains on available-for-sale securities, net of tax	(2)							(2)
Issuance of convertible senior notes	96				96
Conversion of debt	(245)				(245)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)			220
Exercise of stock options and vesting of restricted stock units and performance share units	$ 6		$ 0		6
Repurchase of common stock (in shares)	(682)			(682)
Repurchase of common stock	$ (1,259)			$ (1,259)
Stock-based compensation and other stock-based payments	166				166
Balance (in shares) at Sep. 30, 2020			63,399	(22,444)
Balance at Sep. 30, 2020	4,913		$ 0	$ (24,123)	5,779	23,453		(196)
Balance (in shares) at Jun. 30, 2020			63,391	(22,442)
Balance at Jun. 30, 2020	3,999		$ 0	$ (24,119)	5,699	22,652		(233)
Increase (Decrease) in Stockholders' Equity
Net income	801					801
Foreign currency translation adjustments, net of tax	42							42
Net unrealized (losses) gains on available-for-sale securities, net of tax	(5)							(5)
Exercise of stock options and vesting of restricted stock units and performance share units (in shares)			8
Exercise of stock options and vesting of restricted stock units and performance share units	$ 0		$ 0		0
Repurchase of common stock (in shares)	(2)			(2)
Repurchase of common stock	$ (4)			$ (4)
Stock-based compensation and other stock-based payments	80				80
Balance (in shares) at Sep. 30, 2020			63,399	(22,444)
Balance at Sep. 30, 2020	$ 4,913		$ 0	$ (24,123)	$ 5,779	$ 23,453		$ (196)