Annual report pursuant to Section 13 and 15(d)

Restructuring Charges - Additional Information (Details)

v3.8.0.1
Restructuring Charges - Additional Information (Details)
 3 Months Ended 6 Months Ended 12 Months Ended
Dec. 19, 2016
Employee
Dec. 31, 2017
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Jun. 30, 2016
USD ($)
Mar. 31, 2016
USD ($)
Dec. 31, 2015
Employee
Dec. 31, 2017
USD ($)
Employee
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2018
USD ($)
Restructuring Cost And Reserve [Line Items]                          
Restructuring (charges) credit   $ 4,000 $ 29,000 $ (1,460,000) $ (2,020,000) $ (4,551,000) $ 21,000 $ (36,000)          
Non-cash charges                     $ 817,000    
Impairment of property and equipment                   $ 200,000 200,000    
Leasehold Improvements [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Impairment of property and equipment                   $ 200,000 200,000 $ 0  
Stock-based Compensation [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Non-cash charges                     619,000    
2016 Restructuring [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Number of employees terminated | Employee 57                        
2016 Restructuring [Member] | Leasehold Improvements [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Impairment of property and equipment                     200,000    
2016 Restructuring [Member] | Severance, Other Termination Benefits and Outplacement Services [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Restructuring (charges) credit                     (3,800)    
2016 Restructuring [Member] | Stock-based Compensation [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Non-cash charges                     600,000    
2017 Restructuring [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Number of employees terminated | Employee                   5      
2017 Restructuring [Member] | Forecast [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Expected remaining future payments for restructuring                         $ 100,000
2017 and 2016 Restructuring [Member] | Severance, Other Termination Benefits and Outplacement Services [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Restructuring (charges) credit                   $ (3,400,000)      
2015 Restructuring [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Number of employees terminated | Employee                 52        
2015 Restructuring [Member] | Severance, Other Termination Benefits and Outplacement Services [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Restructuring (charges) credit                     32,000 (2,900,000)  
2015 Restructuring [Member] | Contract Termination Costs [Member]                          
Restructuring Cost And Reserve [Line Items]                          
Restructuring (charges) credit                     $ 29,000 $ 800,000