Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 01, 2015
Stock-Based Compensation
Shares issued under the Employee Stock Purchase Plan (in shares)		$ 467
2004, 2001 and 1992 PLANS
Stock-Based Compensation
Awards available for future grant under the Plan (in shares)		0
2009 Plan
Stock-Based Compensation
Awards available for future grant under the Plan (in shares)		1,090,645
Service-based stock options
Stock-Based Compensation
Vesting period		4 years
Stock-based compensation expense		$ 2,300	$ 2,700	$ 800
Weighted average grant-date fair value (in dollars per share)		$ 2.15	$ 2.22	$ 2.85
Weighted average assumptions used to estimate fair value of each service-based stock option grant
Expected dividend rate		0.00%	0.00%	0.00%
Options
Outstanding at the beginning of the period (in shares)	3,355,692	2,523,400	477,530
Granted (in shares)		1,110,530	2,216,600
Exercised (in shares)		(39,231)	(3,566)
Expired (in shares)		(85,700)	(17,791)
Forfeited (in shares)		(153,307)	(149,373)
Outstanding at the end of the period (in shares)		3,355,692	2,523,400	477,530
Exercisable at the end of the period (in shares)		1,339,675
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 4.66	$ 36.43	$ 21.74
Granted (in dollars per share)		3.01	3.11
Exercised (in dollars per share)		3.06	3.02
Expired (in dollars per share)		35.76	40.02
Forfeited or expired (in dollars per share)		3.61	3.35
Outstanding at the end of the period (in dollars per share)		4.66	$ 36.43	$ 21.74
Exercisable at the end of the period (in dollars per share)		$ 6.99
Weighted Average Remaining Contractual Term
Outstanding		8 years 2 months 12 days	8 years 8 months 12 days	8 years
Aggregate Intrinsic Value
Outstanding		$ 610	$ 5,000	$ 0
Exercised			1,000
Exercisable at end of period		106
Additional disclosures
Total unrecognized compensation cost		$ 2,400
Weighted average period over which unrecognized compensation is expected to be recognized		2 years 9 months
Total fair value of options vested		$ 2,200	$ 1,700	$ 1,500
Service-based stock options | Minimum
Weighted average assumptions used to estimate fair value of each service-based stock option grant
Expected stock price volatility		78.70%	77.40%	82.40%
Risk-free interest rate		1.10%	1.50%	1.70%
Expected life		5 years 6 months	5 years	5 years 6 months
Service-based stock options | Maximum
Stock-Based Compensation
Expiration period		10 years
Weighted average assumptions used to estimate fair value of each service-based stock option grant
Expected stock price volatility		92.20%	88.10%	88.20%
Risk-free interest rate		2.10%	2.00%	2.20%
Expected life		6 years 3 months 18 days	6 years 3 months 18 days	6 years 3 months 18 days
Service-based stock options | Non-employee
Stock-Based Compensation
Expiration period		10 years
Vesting period		1 year
Options
Granted (in shares)		90,000
Service-based stock options | 2009 Plan
Stock-Based Compensation
Vesting period		4 years
Employee stock
Stock-Based Compensation
Common stock available for issuance (in shares)					1,000,000
Stock-based compensation expense		$ 200
Employee stock | Subsequent event
Stock-Based Compensation
Shares purchased during period (in shares)	34,392
Shares issued under the Employee Stock Purchase Plan (in shares)	$ 100