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	71,848				71,848
Net change in unrealized gains (losses) from investments	84			84
Net change in foreign currency translation adjustment	409			409
Issuance of common stock relating to employee equity compensation plans (in shares)		427
Issuance of common stock relating to employee equity compensation plans	9,609		9,609
Tax withholdings related to net share settlements of equity awards	(50,181)		(50,181)
Common stock repurchased and retired (shares)		(205)
Stock Repurchased and Retired During Period, Value	(50,000)		(2,030)		(47,970)
Stock-based compensation	21,044		21,044
Ending Balance (in shares) at Mar. 31, 2019		80,000
Ending Balance at Mar. 31, 2019	1,255,704	$ 8	855,956	(2,281)	402,021
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,518,131				1,518,131
Net change in unrealized gains (losses) from investments	(194)			(194)
Net change in foreign currency translation adjustment	689			689
Issuance of common stock relating to employee equity compensation plans (in shares)		326
Issuance of common stock relating to employee equity compensation plans	10,662		10,662
Tax withholdings related to net share settlements of equity awards	(45,395)		(45,395)
Stock-based compensation	22,927		22,927
Ending Balance (in shares) at Mar. 31, 2020		78,759
Ending Balance at Mar. 31, 2020	$ 2,852,989	$ 8	$ 895,131	$ (193)	$ 1,958,043