Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings (Accumulated Deficit) [Member]
BALANCE at Dec. 31, 2013	$ 455,384	$ 819	$ (214,494)	$ 600,904	$ (503)	$ 68,658
BALANCE, shares at Dec. 31, 2013			(14,719,000)
BALANCE, shares at Dec. 31, 2013		81,890,000
Net income (loss)	(178,163)					(178,163)
Unrealized gain (loss) on investments	(350)				(350)
COMPREHENSIVE (LOSS) INCOME	(178,513)
Share-based compensation expense:
Stock option plan	1,372			1,372
Restricted stock award plan	2,865			2,865
Employee stock purchase plan	40			40
Common stock issued under:
Stock option plan	$ 612	$ 2		610
Stock option plan, shares	225,000	225,000
Restricted stock award plan	$ (671)	$ 1	$ (671)	(1)
Restricted stock award plan, shares		95,000	(97,000)
Employee stock purchase plan	742	$ 1		741
Employee stock purchase plan, shares		127,000
Cumulative adjustment for change from cost method investment to equity method investment	102					102
BALANCE at Dec. 31, 2014	281,933	$ 823	$ (215,165)	606,531	(853)	(109,403)
BALANCE, shares at Dec. 31, 2014			(14,816,000)
BALANCE, shares at Dec. 31, 2014		82,337,000
Net income (loss)	51,885					51,885
Unrealized gain (loss) on investments	(27)				(27)
COMPREHENSIVE (LOSS) INCOME	51,858
Share-based compensation expense:
Stock option plan	442			442
Restricted stock award plan	2,385			2,385
Employee stock purchase plan	30			30
Common stock issued under:
Stock option plan	$ 828	$ 3		825
Stock option plan, shares	303,035	303,000
Restricted stock award plan	$ (439)	$ 2	$ (441)
Restricted stock award plan, shares		214,000	(82,000)
Employee stock purchase plan	573	$ 2		571
Employee stock purchase plan, shares		143,000
BALANCE at Dec. 31, 2015	$ 337,610	$ 830	$ (215,606)	610,784	(880)	(57,518)
BALANCE, shares at Dec. 31, 2015	(14,897,931)		(14,898,000)
BALANCE, shares at Dec. 31, 2015	82,996,585	82,997,000
Net income (loss)	$ (18,712)					(18,712)
Foreign currency translation	(77)				(77)
Unrealized gain (loss) on investments	699				699
COMPREHENSIVE (LOSS) INCOME	(18,090)
Share-based compensation expense:
Stock option plan	1,256			1,256
Restricted stock award plan	1,960			1,960
Employee stock purchase plan	21			21
Common stock issued under:
Stock option plan	$ 375	$ 1		374
Stock option plan, shares	89,773	90,000
Restricted stock award plan	$ (563)	$ 3	$ (563)	(3)
Restricted stock award plan, shares		387,000	(121,000)
Employee stock purchase plan	398	$ 1		397
Employee stock purchase plan, shares		64,000
Tax benefit of stock settlements	(1,464)			(1,464)
BALANCE at Dec. 31, 2016	$ 321,503	$ 835	$ (216,169)	$ 613,325	$ (258)	$ (76,230)
BALANCE, shares at Dec. 31, 2016	(15,019,028)		(15,019,000)
BALANCE, shares at Dec. 31, 2016	83,538,033	83,538,000