Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive (loss) income	Common Stock in Treasury
Beginning balance (in shares) at Dec. 31, 2015		299,113,000
Beginning balance at Dec. 31, 2015	$ 1,973,446	$ 299	$ 4,566,919	$ 3,474,625	$ (28,527)	$ (6,039,870)
Beginning balance, treasury shares (in shares) at Dec. 31, 2015						(145,296,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock-based compensation plans	41,247	$ 3	41,244
Shares issued under stock-based compensation plans (in shares)		3,009,000
Stock-based compensation expense	175,980		175,980
Common stock issued under employee stock purchase plan	57,515	$ 1	57,514
Common stock issued under employee stock purchase plan (in shares)		729,000
Temporary equity reclassification	(79,495)		(79,495)
Stock repurchases, net	(28,689)					$ (28,689)
Stock repurchases, net (in shares)						(426,000)
Tax deficiency from employer stock plans, net	(574)		(574)
Restricted shares turned in for tax withholding	$ (66,638)					$ (66,638)
Restricted shares turned in for tax withholding (in shares)	(830,155)					(830,000)
Other comprehensive income (loss), net of tax	$ (177)				(177)
Net income (loss)	536,112			536,112
Ending balance (in shares) at Dec. 31, 2016		302,851,000
Ending balance at Dec. 31, 2016	2,608,727	$ 303	4,761,588	4,010,737	(28,704)	$ (6,135,197)
Ending balance, treasury shares (in shares) at Dec. 31, 2016						(146,552,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock-based compensation plans	2,113	$ 3	2,110
Shares issued under stock-based compensation plans (in shares)		2,614,000
Stock-based compensation expense	166,308		166,308
Common stock issued under employee stock purchase plan	19,326		19,326
Common stock issued under employee stock purchase plan (in shares)		286,000
Temporary equity reclassification	79,495		79,495
Stock repurchases, net	(574,956)					$ (574,956)
Stock repurchases, net (in shares)						(7,384,000)
Accelerated stock repurchase program	(750,000)		(150,000)			$ (600,000)
Accelerated stock repurchase program (shares)						(7,133,000)
Restricted shares turned in for tax withholding	$ (80,040)					$ (80,040)
Restricted shares turned in for tax withholding (in shares)	(974,501)					(975,000)
Cumulative-effect adjustment from adoption of accounting standards	$ 388		5,691	(5,303)
Distribution of the net assets of the GoTo Business	(461,831)			(475,231)	13,400
Other	(848)		(848)
Other comprehensive income (loss), net of tax	4,498				4,498
Net income (loss)	(20,719)			(20,719)
Ending balance (in shares) at Dec. 31, 2017		305,751,000
Ending balance at Dec. 31, 2017	$ 992,461	$ 306	4,883,670	3,509,484	(10,806)	$ (7,390,193)
Ending balance, treasury shares (in shares) at Dec. 31, 2017	(162,044,000)					(162,044,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock-based compensation plans	$ 164	$ 3	161
Shares issued under stock-based compensation plans (in shares)		2,258,000
Stock-based compensation expense	203,619		203,619
Common stock issued under employee stock purchase plan	33,462		33,462
Common stock issued under employee stock purchase plan (in shares)		461,000
Temporary equity reclassification	(8,110)		(8,110)
Stock repurchases, net	(511,153)					$ (511,153)
Stock repurchases, net (in shares)						(4,731,000)
Accelerated stock repurchase program	(750,000)		150,000			$ (900,000)
Accelerated stock repurchase program (shares)						(9,522,000)
Restricted shares turned in for tax withholding	$ (71,593)					$ (71,593)
Restricted shares turned in for tax withholding (in shares)	(739,522)					(739,000)
Cash dividends declared	$ (46,799)			(46,799)
Settlement of convertible notes and hedges		$ 1	138,231
Settlement of convertible notes and hedges	(2,985)					$ (141,217)
Settlement of convertible notes and hedges (shares)		1,291,000
Settlement of convertible notes and hedges (shares)						1,291,000
Cumulative-effect adjustment from adoption of accounting standards	132,778			132,778
Other	1,356		3,467	(2,111)
Other comprehensive income (loss), net of tax	2,652				2,652
Net income (loss)	575,667			575,667
Ending balance (in shares) at Dec. 31, 2018		309,761,000
Ending balance at Dec. 31, 2018	$ 551,519	$ 310	$ 5,404,500	$ 4,169,019	$ (8,154)	$ (9,014,156)
Ending balance, treasury shares (in shares) at Dec. 31, 2018	(178,327,000)					(178,327,000)