Annual report pursuant to Section 13 and 15(d)

Consolidated Financial Statement Detail - Additional Information 2 (Details)

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Consolidated Financial Statement Detail - Additional Information 2 (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]      
Depreciation and amortization expense $ 300,000 $ 800,000 $ 1,500,000
Total proceeds from sale of equipment and disposal of certain equipment 1,614,000 49,000 18,000
Total carrying value of equipment sold and disposed 400,000    
Impairment of property and equipment 200,000 200,000  
Other Income (Expense) [Member]      
Property, Plant and Equipment [Line Items]      
Gain on sale and disposal of equipment $ 1,200,000    
Equipment and Furniture [Member]      
Property, Plant and Equipment [Line Items]      
Property and equipment under capital lease   300,000  
Accumulated amortization   100,000  
Capital lease agreement termination date 2017-03    
Leasehold Improvements [Member]      
Property, Plant and Equipment [Line Items]      
Impairment of property and equipment $ 200,000 $ 200,000 $ 0