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Stock-Based Compensation (Details 2) - USD ($)
$ in Thousands
12 Months Ended
Jan. 02, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Stock-based compensation        
Weighted average period over which unrecognized compensation expense is expected to be recognized   2 years 6 months 15 days    
Stock options | Employee and Director        
Stock-based compensation        
Stock-based compensation expense   $ 2,128 $ 2,276 $ 3,122
Stock-based compensation expense, net of estimated forfeitures, related to unvested awards not yet recognized   $ 3,488    
Weighted average period over which unrecognized compensation expense is expected to be recognized   2 years    
Assumptions used to determine fair value of stock options        
Expected dividend yield (as a percent)   0.00% 0.00% 0.00%
Risk-free rate, minimum (as a percent)   1.32% 0.01% 0.71%
Risk-free rate, maximum (as a percent)   1.69% 2.41% 2.05%
Volatility, minimum (as a percent)   88.00% 84.00% 84.00%
Volatility, maximum (as a percent)   91.00% 85.00% 85.00%
Stock options | Minimum        
Assumptions used to determine fair value of stock options        
Vesting period for options granted   1 year    
Stock options | Minimum | Employee and Director        
Assumptions used to determine fair value of stock options        
Expected option term (in years)   5 years 6 months 21 days 6 years
Stock options | Maximum        
Assumptions used to determine fair value of stock options        
Vesting period for options granted   4 years    
Stock options | Maximum | Employee and Director        
Assumptions used to determine fair value of stock options        
Expected option term (in years)   5 years 10 months 24 days 6 years 1 month 6 days 6 years 1 month 6 days
Restricted Stock Units (RSUs) | Chief Executive Officer        
Assumptions used to determine fair value of stock options        
Number of shares awarded during period 100,000      
Vesting period for options granted 3 years      
Fair value of awards granted during period $ 327