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Summary of Significant Accounting Policies - Additional Information (Detail)
 3 Months Ended 12 Months Ended
Mar. 31, 2018
USD ($)
Customer
Segment
Mar. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
Customer
Summary Of Significant Accounting Policies [Line Items]      
Description of payment of customer invoice contract The Company invoices its customers based upon the payment terms in the contracts, which is generally from 30 to 60 days.    
Contract asset $ 0   $ 0
Restricted cash $ 2,500,000    
Number of major customers representing outstanding trade receivables | Customer 3   3
Protracted length of inventory 1 year    
Inventory valuation reserves $ 200,000   $ 200,000
Accumulated amortization intangible assets $ 1,530   1,480
Estimated useful life of intangible assets 10 years    
Number of reportable segments | Segment 1    
Impairment charges acquired intangible asstes $ 0 $ 0  
Period of warranty 1 year    
Warranty claim liability $ 0   $ 0
Trade Accounts Receivable | Customer Concentration Risk      
Summary Of Significant Accounting Policies [Line Items]      
Concentration risk, percentage 57.00%   53.00%
Minimum      
Summary Of Significant Accounting Policies [Line Items]      
Payment of customer invoice contract period 30 days    
Shelf lives of inventory 18 months    
Estimated useful life of property and equipment 3 years    
Maximum      
Summary Of Significant Accounting Policies [Line Items]      
Payment of customer invoice contract period 60 days    
Shelf lives of inventory 24 months    
Estimated useful life of property and equipment 5 years