CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Treasury Stock	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2019		162,000,843
Beginning balance at Dec. 31, 2019	$ 3,657,958	$ 1,620	$ 3,653,486	$ (45,144)	$ 0	$ 47,996
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes (in shares)		1,667,888
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes	(76,679)	$ 17	(76,696)
Issuance of common stock under employee stock purchase plan (in shares)		393,921
Issuance of common stock under employee stock purchase plan	29,170	$ 4	29,166
Stock-based compensation	175,272		175,272
Repurchases of common stock (in shares)		(1,262,868)
Repurchases of common stock	(121,078)				(121,078)
Net income	443,684					443,684
Foreign currency translation adjustments	(7,292)			(7,292)
Change in unrealized gain (loss) on investments, net of tax	6,582			6,582
Ending balance (in shares) at Sep. 30, 2020		162,799,784
Ending balance at Sep. 30, 2020	4,107,617	$ 1,641	3,781,228	(45,854)	(121,078)	491,680
Beginning balance (in shares) at Jun. 30, 2020		162,630,477
Beginning balance at Jun. 30, 2020	3,904,295	$ 1,638	3,734,787	(57,307)	(107,880)	333,057
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes (in shares)		289,304
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes	(13,387)	$ 3	(13,390)
Stock-based compensation	59,831		59,831
Repurchases of common stock (in shares)		(119,997)
Repurchases of common stock	(13,198)				(13,198)
Net income	158,623					158,623
Foreign currency translation adjustments	13,177			13,177
Change in unrealized gain (loss) on investments, net of tax	(1,724)			(1,724)
Ending balance (in shares) at Sep. 30, 2020		162,799,784
Ending balance at Sep. 30, 2020	4,107,617	$ 1,641	3,781,228	(45,854)	(121,078)	491,680
Beginning balance (in shares) at Dec. 31, 2020		162,709,720
Beginning balance at Dec. 31, 2020	4,251,296	$ 1,627	3,664,820	(20,201)	0	605,050
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes (in shares)		1,665,123
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes	(88,747)	$ 16	(88,763)
Issuance of common stock under employee stock purchase plan (in shares)		358,384
Issuance of common stock under employee stock purchase plan	31,531	$ 4	31,527
Stock-based compensation	182,039		182,039
Repurchases of common stock (in shares)		(2,308,787)
Repurchases of common stock	(251,257)				(251,257)
Net income	491,108					491,108
Foreign currency translation adjustments	(28,444)			(28,444)
Change in unrealized gain (loss) on investments, net of tax	(5,081)			(5,081)
Ending balance (in shares) at Sep. 30, 2021		162,424,440
Ending balance at Sep. 30, 2021	4,582,445	$ 1,647	3,789,623	(53,726)	(251,257)	1,096,158
Beginning balance (in shares) at Jun. 30, 2021		163,018,768
Beginning balance at Jun. 30, 2021	4,476,657	$ 1,645	3,743,743	(31,557)	(154,416)	917,242
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes (in shares)		252,204
Issuance of common stock upon the exercise of stock options and vesting of restricted and deferred stock units, net of shares withheld for employee taxes	(11,866)	$ 2	(11,868)
Stock-based compensation	57,748		57,748
Repurchases of common stock (in shares)		(846,532)
Repurchases of common stock	(96,841)				(96,841)
Net income	178,916					178,916
Foreign currency translation adjustments	(21,160)			(21,160)
Change in unrealized gain (loss) on investments, net of tax	(1,009)			(1,009)
Ending balance (in shares) at Sep. 30, 2021		162,424,440
Ending balance at Sep. 30, 2021	$ 4,582,445	$ 1,647	$ 3,789,623	$ (53,726)	$ (251,257)	$ 1,096,158