CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss), Net	Retained Earnings
Beginning Balance (in shares) at Dec. 31, 2018		79,778
Beginning Balance at Dec. 31, 2018	$ 1,252,891	$ 8	$ 877,514	$ (2,774)	$ 378,143
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	218,990				218,990
Net change in unrealized gains (losses) from investments	276			276
Change in foreign currency translation adjustment, net of tax	622			622
Issuance of common stock relating to employee equity compensation plans (in shares)		453
Issuance of common stock relating to employee equity compensation plans	9,614		9,614
Tax withholdings related to net share settlements of equity awards	(52,718)		(52,718)
Common stock repurchased and retired (shares)		(366)
Stock Repurchased and Retired During Period, Value	(99,504)		(3,646)		(95,858)
Stock-based compensation	43,511		43,511
Ending Balance (in shares) at Jun. 30, 2019		79,865
Ending Balance at Jun. 30, 2019	1,373,682	$ 8	874,275	(1,876)	501,275
Beginning Balance (in shares) at Dec. 31, 2018		79,778
Beginning Balance at Dec. 31, 2018	1,252,891	$ 8	877,514	(2,774)	378,143
Ending Balance (in shares) at Dec. 31, 2019		78,433
Ending Balance at Dec. 31, 2019	1,346,169	$ 8	906,937	(688)	439,912
Beginning Balance (in shares) at Mar. 31, 2019		80,000
Beginning Balance at Mar. 31, 2019	1,255,704	$ 8	855,956	(2,281)	402,021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	147,142				147,142
Net change in unrealized gains (losses) from investments	192			192
Change in foreign currency translation adjustment, net of tax	213			213
Issuance of common stock relating to employee equity compensation plans (in shares)		26
Issuance of common stock relating to employee equity compensation plans	5		5
Tax withholdings related to net share settlements of equity awards	(2,537)		(2,537)
Common stock repurchased and retired (shares)		(161)
Stock Repurchased and Retired During Period, Value	(49,504)		(1,616)		(47,888)
Stock-based compensation	22,467		22,467
Ending Balance (in shares) at Jun. 30, 2019		79,865
Ending Balance at Jun. 30, 2019	1,373,682	$ 8	874,275	(1,876)	501,275
Beginning Balance (in shares) at Dec. 31, 2019		78,433
Beginning Balance at Dec. 31, 2019	1,346,169	$ 8	906,937	(688)	439,912
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,477,529				1,477,529
Net change in unrealized gains (losses) from investments	(194)			(194)
Change in foreign currency translation adjustment, net of tax	9,983			9,983
Issuance of common stock relating to employee equity compensation plans (in shares)		348
Issuance of common stock relating to employee equity compensation plans	10,662		10,662
Tax withholdings related to net share settlements of equity awards	(47,038)		(47,038)
Stock-based compensation	47,934		47,934
Ending Balance (in shares) at Jun. 30, 2020		78,781
Ending Balance at Jun. 30, 2020	2,845,045	$ 8	918,495	9,101	1,917,441
Beginning Balance (in shares) at Mar. 31, 2020		78,759
Beginning Balance at Mar. 31, 2020	2,852,989	$ 8	895,131	(193)	1,958,043
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	(40,602)				(40,602)
Change in foreign currency translation adjustment, net of tax	9,294			9,294
Issuance of common stock relating to employee equity compensation plans (in shares)		22
Issuance of common stock relating to employee equity compensation plans	0		0
Tax withholdings related to net share settlements of equity awards	(1,643)		(1,643)
Stock-based compensation	25,007		25,007
Ending Balance (in shares) at Jun. 30, 2020		78,781
Ending Balance at Jun. 30, 2020	$ 2,845,045	$ 8	$ 918,495	$ 9,101	$ 1,917,441