CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Thousands, $ in Thousands		Total	Accumulated Deficit [Member]	AOCI Attributable to Parent [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2014		$ 257,827	$ (544,746)	$ 0	$ 2,157	$ 819,757	$ (19,341)
Beginning Balance (in shares) at Dec. 31, 2014					21,573		921
Net loss		(59,524)	(59,524)
Stock options exercised, net of tax withholdings		676				(1,051)	$ 1,727
Stock options exercised, net (in shares)							83
Issuance of restricted stock, net of tax withholdings		158				(2,883)	$ 3,041
Issuance of restricted stock, net (in shares)							(149)
Stock-based compensation expense		1,611				1,611
Repurchase of common stock		(4,997)					$ (4,997)
Repurchase of common stock (in shares)							304
Other comprehensive income (loss)		(246)		(246)
Ending Balance at Dec. 31, 2015		195,505	(604,270)	(246)	$ 2,157	817,434	$ (19,570)
Ending Balance (in shares) at Dec. 31, 2015					21,573		993
Cumulative effect adjustment	[1]		(372)			372
Net loss		(22,262)	(22,262)
Stock options exercised, net of tax withholdings		(318)				(1,117)	$ 799
Stock options exercised, net (in shares)							46
Issuance of restricted stock, net of tax withholdings		32				(3,067)	$ 3,099
Issuance of restricted stock, net (in shares)							(162)
Stock-based compensation expense		2,394				2,394
Repurchase of common stock		(5,389)					$ (5,389)
Repurchase of common stock (in shares)							424
Other comprehensive income (loss)		(185)		(185)
Ending Balance at Dec. 31, 2016		169,777	(626,904)	(431)	$ 2,157	816,016	$ (21,061)
Ending Balance (in shares) at Dec. 31, 2016					21,573		1,209
Net loss		(88,572)	(88,572)
Stock options exercised, net of tax withholdings		(1)				(97)	$ 96
Stock options exercised, net (in shares)							6
Issuance of restricted stock, net of tax withholdings		(38)				(3,695)	$ 3,657
Issuance of restricted stock, net (in shares)							(204)
Stock-based compensation expense		1,138				1,138
Repurchase of convertible senior debentures		(826)				(826)
Other comprehensive income (loss)		318		318
Ending Balance at Dec. 31, 2017		$ 81,796	$ (715,476)	$ (113)	$ 2,157	$ 812,536	$ (17,308)
Ending Balance (in shares) at Dec. 31, 2017					21,573		999

[1] Cumulative effect adjustment reflects adoption of ASU 2016-09 as of January 1, 2016.