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, 2016		79,553
Beginning Balance at Dec. 31, 2016	$ 999,307	$ 8	$ 864,871	$ (938)	$ 135,366
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	231,418				231,418
Net change in unrealized gains (losses) from investments	(232)			(232)
Net change in foreign currency translation adjustment	1,741		0	1,741
Issuance of common stock relating to employee equity compensation plans (in shares)		1,073
Issuance of common stock relating to employee equity compensation plans	14,461	$ 0	14,461
Tax withholdings related to net share settlements of equity awards	(46,168)		(46,168)
Common stock repurchased and retired (shares)		(586)
Common stock repurchased and retired	(103,793)		(5,583)		(98,210)
Stock-based compensation	58,854		58,854
Ending Balance (in shares) at Dec. 31, 2017		80,040
Ending Balance at Dec. 31, 2017	1,154,288	$ 8	886,435	571	267,274
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	400,235				400,235
Net change in unrealized gains (losses) from investments	286			286
Net change in foreign currency translation adjustment	(3,631)		0	(3,631)
Issuance of common stock relating to employee equity compensation plans (in shares)		795
Issuance of common stock relating to employee equity compensation plans	16,635	$ 0	16,635
Tax withholdings related to net share settlements of equity awards	(86,067)		(86,067)
Common stock repurchased and retired (shares)		(1,057)
Common stock repurchased and retired	(300,002)		(10,252)		(289,750)
Stock-based compensation	70,763		70,763
Ending Balance (in shares) at Dec. 31, 2018		79,778
Ending Balance at Dec. 31, 2018	1,252,891	$ 8	877,514	(2,774)	378,143
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment from adoption of ASU	384
Net income	442,776
Net change in unrealized gains (losses) from investments	299			299
Net change in foreign currency translation adjustment	1,787			1,787
Issuance of common stock relating to employee equity compensation plans (in shares)		542
Issuance of common stock relating to employee equity compensation plans	17,907		17,907
Tax withholdings related to net share settlements of equity awards	(57,676)		(57,676)
Common stock repurchased and retired (shares)		(1,887)
Common stock repurchased and retired	(399,999)		(18,992)		(381,007)
Stock-based compensation	88,184		88,184
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