CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Employees and Directors	Non-employee	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Employees and Directors	Additional Paid-in Capital Non-employee	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2016				112,710
Beginning balance at Dec. 31, 2016	$ 41,379			$ 113	$ 363,534			$ 0	$ 0	$ (322,268)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options (in shares)	2,007			2,007
Issuance of common stock upon exercise of options	$ 7,181			$ 2	7,179
Stock-based compensation related to employee and director options		$ 13,330	$ 31			$ 13,330	$ 31
Other comprehensive loss, net of tax	(75)								(75)
Net income	129,122									129,122
Ending balance at Dec. 31, 2017	$ 190,968			$ 115	384,074			0	(75)	(193,146)
Ending balance (in shares) at Dec. 31, 2017				114,717
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options (in shares)	2,121			2,121
Issuance of common stock upon exercise of options	$ 9,322			$ 2	9,320
Stock-based compensation related to employee and director options		23,834				23,834
Other comprehensive loss, net of tax	5								5
Purchases of treasury stock (in shares)				(1,807)
Purchase of treasury stock	(23,657)							(23,657)
Net income	75,410									75,410
Ending balance at Dec. 31, 2018	$ 275,882			$ 117	417,228			(23,657)	(70)	(117,736)
Ending balance (in shares) at Dec. 31, 2018				115,031
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options (in shares)	2,929			2,929
Issuance of common stock upon exercise of options	$ 10,402			$ 3	10,399
Shares tendered to satisfy cost and statutory withholding requirements for net settlement of cashless option exercises (in shares)				(631)
Shares tendered to satisfy cost and statutory withholding requirements for net settlement of cashless option exercises	(8,072)							(8,072)
Stock-based compensation related to employee and director options		$ 29,201	$ 232			$ 29,201	$ 232
Other comprehensive loss, net of tax	331								331
Purchases of treasury stock (in shares)				(2,780)
Purchase of treasury stock	(30,975)							(30,975)
Net income	94,181									94,181
Ending balance at Dec. 31, 2019	$ 371,182			$ 120	$ 457,060			$ (62,704)	$ 261	$ (23,555)
Ending balance (in shares) at Dec. 31, 2019				114,549