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)		1,378,584
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	(63,292)	$ 14	(63,306)
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	115,441		115,441
Repurchases of common stock (in shares)		(1,142,871)
Repurchases of common stock	(107,880)				(107,880)
Net income	285,061					285,061
Foreign currency translation adjustments	(20,469)			(20,469)
Change in unrealized gain (loss) on investments, net of tax	8,306			8,306
Ending balance (in shares) at Jun. 30, 2020		162,630,477
Ending balance at Jun. 30, 2020	3,904,295	$ 1,638	3,734,787	(57,307)	(107,880)	333,057
Beginning balance (in shares) at Mar. 31, 2020		162,176,589
Beginning balance at Mar. 31, 2020	3,672,218	$ 1,631	3,658,990	(78,995)	(80,550)	171,142
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)		331,544
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	(12,592)	$ 3	(12,595)
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	59,226		59,226
Repurchases of common stock (in shares)		(271,577)
Repurchases of common stock	(27,330)				(27,330)
Net income	161,915					161,915
Foreign currency translation adjustments	5,808			5,808
Change in unrealized gain (loss) on investments, net of tax	15,880			15,880
Ending balance (in shares) at Jun. 30, 2020		162,630,477
Ending balance at Jun. 30, 2020	3,904,295	$ 1,638	3,734,787	(57,307)	(107,880)	333,057
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)		1,412,919
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	(76,881)	$ 14	(76,895)
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	124,291		124,291
Repurchases of common stock (in shares)		(1,462,255)
Repurchases of common stock	(154,416)				(154,416)
Net income	312,192					312,192
Foreign currency translation adjustments	(7,284)			(7,284)
Change in unrealized gain (loss) on investments, net of tax	(4,072)			(4,072)
Ending balance (in shares) at Jun. 30, 2021		163,018,768
Ending balance at Jun. 30, 2021	4,476,657	$ 1,645	3,743,743	(31,557)	(154,416)	917,242
Beginning balance (in shares) at Mar. 31, 2021		163,245,941
Beginning balance at Mar. 31, 2021	4,321,363	$ 1,638	3,664,568	(47,347)	(58,241)	760,745
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)		284,735
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	(12,875)	$ 3	(12,878)
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	60,526		60,526
Repurchases of common stock (in shares)		(870,292)
Repurchases of common stock	(96,175)				(96,175)
Net income	156,497					156,497
Foreign currency translation adjustments	16,981			16,981
Change in unrealized gain (loss) on investments, net of tax	(1,191)			(1,191)
Ending balance (in shares) at Jun. 30, 2021		163,018,768
Ending balance at Jun. 30, 2021	$ 4,476,657	$ 1,645	$ 3,743,743	$ (31,557)	$ (154,416)	$ 917,242