Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Total
Balance at December 31 at Dec. 31, 2011	$ 457	$ 367,829	$ 40	$ (353,520)	$ 14,806
Net loss				(39,081)	(39,081)
Other comprehensive loss			(13)		(13)
Exercise of stock options,	3	536			539
Employee stock purchase plan sales,	1	320			321
Issuance of common stock,	48	18,759			18,807
Stock-based compensation expense		4,167			4,167
Balance at December 31 at Dec. 31, 2012	509	391,611	27	(392,601)	(454)
Net loss				(30,108)	(30,108)
Other comprehensive loss			(23)		(23)
Exercise of stock options,	6	1,327			1,333
Employee stock purchase plan sales,	1	123			124
Issuance of common stock,	75	23,559			23,634
Stock-based compensation expense		4,368			4,368
Balance at December 31 at Dec. 31, 2013	591	420,988	4	(422,709)	(1,126)
Net loss				(45,189)	(45,189)
Other comprehensive loss			(134)		(134)
Exercise of stock options,	13	4,984			4,997
Employee stock purchase plan sales,	1	309			310
Issuance of common stock,	115	106,485			106,600
Stock-based compensation expense		10,177			10,177
Balance at December 31 at Dec. 31, 2014	$ 720	$ 542,943	$ (130)	$ (467,898)	$ 75,635