Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance 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 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 Dec. 31, 2014	720	542,943	(130)	(467,898)	75,635
Net loss				(43,019)	(43,019)
Other comprehensive loss			(76)		(76)
Exercise of stock options	14	5,110			5,124
Employee stock purchase plan sales		355			355
Stock-based compensation expense		9,705			9,705
Balance at Dec. 31, 2015	$ 734	$ 558,113	$ (206)	$ (510,917)	$ 47,724