Consolidated Statements Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (shares) at Dec. 31, 2013		38,351
Beginning balance at Dec. 31, 2013	$ 41,483	$ 4	$ 298,370	$ (32)	$ (256,859)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (shares)		146
Exercise of stock options	195		195
Cancellation of shares (shares)		(456)
Cancellation of shares	(806)		(806)
Release of stock awards (shares)		1,522
Employee stock-based compensation	4,608		4,608
Non-employee stock-based compensation	12		12
Total comprehensive loss	(19,181)			(110)	(19,071)
Ending balance (shares) at Dec. 31, 2014		39,563
Ending balance at Dec. 31, 2014	26,311	$ 4	302,379	(142)	(275,930)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (shares)		172
Exercise of stock options	289		289
Cancellation of shares (shares)		(444)
Cancellation of shares	(1,813)		(1,813)
Release of stock awards (shares)		1,052
Employee stock-based compensation	5,122		5,122
Non-employee stock-based compensation	4		4
Total comprehensive loss	(7,034)			547	(7,581)
Ending balance (shares) at Dec. 31, 2015		40,343
Ending balance at Dec. 31, 2015	$ 22,879	$ 4	305,981	405	(283,511)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (shares)	398	398
Exercise of stock options	$ 1,034		1,034
Cancellation of shares (shares)		(397)
Cancellation of shares	(1,524)		(1,524)
Release of stock awards (shares)		911
Employee stock-based compensation	5,673		5,673
Total comprehensive loss	(8,963)			(405)	(8,558)
Ending balance (shares) at Dec. 31, 2016		41,255
Ending balance at Dec. 31, 2016	$ 19,099	$ 4	$ 311,164	$ 0	$ (292,069)