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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
Share data in Millions, unless otherwise specified
 3 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended
Mar. 31, 2014
Segment
Customer
Mar. 31, 2013
Dec. 31, 2013
Customer
Aug. 31, 2009
2009 Unit Offering
Nov. 30, 2010
2010 Unit Offering
Mar. 31, 2014
Trade Accounts Receivable
Dec. 31, 2013
Trade Accounts Receivable
Mar. 31, 2014
Minimum
Mar. 31, 2014
Maximum
Summary Of Significant Accounting Policies [Line Items]                  
Deferred revenue $ 279,000   $ 181,000 [1]            
Number of major customers representing outstanding trade receivables 3   2            
Cumulative outstanding trade receivables percentage by major customers           65.00% 55.00%    
Life of inventory 2 years                
Protracted length of inventory 1 year                
Inventory valuation reserves 300,000   400,000            
Estimated useful life of property and equipment               3 years 5 years
Estimated useful life of intangible assets 10 years                
Number of operating segments 1                
Number of reportable segments 1                
Impairment charges on long-lived assets 0 0              
Foreign exchange gain (loss) $ 100,000 $ (100,000)              
Warrants to purchase an aggregate shares of common stock       2.4 3.7        
Derecognition of tax positions, Maximum                 50.00%
Company's tax years subject to examination by the taxing jurisdictions               1998 2013
Period of warranty 1 year                
[1] The financial information in this column was derived from audited financial statements included in the Company's 2013 Annual Report on Form 10-K.