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, 2014		294,674,000
Beginning balance at Dec. 31, 2014	$ 2,173,645	$ 295	$ 4,292,706	$ 3,155,264	$ (36,790)	$ (5,237,830)
Beginning balance, treasury shares (in shares) at Dec. 31, 2014						(133,898,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under stock-based compensation plans	112,285	$ 3	112,282
Shares issued under stock-based compensation plans (in shares)		3,878,000
Stock-based compensation expense	139,816		139,816
Common stock issued under employee stock purchase plan	37,229	$ 1	37,228
Common stock issued under employee stock purchase plan (in shares)		561,000
Tax deficiency from employer stock plans, net	(15,013)		(15,013)
Stock repurchases, net	(755,704)					$ (755,704)
Stock repurchases, net (in shares)						(10,717,000)
Restricted shares turned in for tax withholding	$ (46,336)					$ (46,336)
Restricted shares turned in for tax withholding (in shares)	(679,694)					(681,000)
Other comprehensive income (loss), net of tax	$ 8,263				8,263
Other	(100)		(100)
Net (loss) income	319,361			319,361
Ending balance (in shares) at Dec. 31, 2015		299,113,000
Ending balance at Dec. 31, 2015	1,973,446	$ 299	4,566,919	3,474,625	(28,527)	$ (6,039,870)
Ending 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
Tax deficiency from employer stock plans, net	(574)		(574)
Stock repurchases, net	(28,689)					$ (28,689)
Stock repurchases, net (in shares)						(426,000)
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)
Equity component of convertible note issuance	(79,495)		(79,495)
Net (loss) income	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)					(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	$ 0	19,326
Common stock issued under employee stock purchase plan (in shares)		286,000
Stock repurchases, net	(574,956)					$ (574,956)
Stock repurchases, net (in shares)						(7,384,000)
Restricted shares turned in for tax withholding	(80,040)					$ (80,040)
Accelerated stock repurchase program	(750,000)		(150,000)			$ (600,000)
Accelerated stock repurchase program (shares)						(7,133,000)
Cumulative-effect adjustment from adoption of accounting standard on stock-based compensation	388		5,691	(5,303)
Distribution of the net assets of the GoTo Business	$ (461,831)			(475,231)	13,400
Restricted shares turned in for tax withholding (in shares)	(974,501)					(975,000)
Other comprehensive income (loss), net of tax	$ 4,498				4,498
Other	(848)		(848)
Equity component of convertible note issuance	79,495		79,495
Net (loss) income	(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)