Income Taxes - Narrative (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Income Tax Disclosure [Abstract]        
Provision for income taxes $ 17,000 $ 51,000 $ 43,000  
Provision for foreign tax expense 16,000      
State 1,000 1,000 1,000  
Undistributed earnings of foreign subsidiaries 300,000      
Valuation allowance (35,496,000) (29,199,000)    
Increase in valuation allowance 6,300,000 2,100,000    
Income Tax Contingency [Line Items]        
Tax Credit Carryforward, Term 20 years      
Unrecognized tax benefits 2,656,000 1,840,000 1,401,000 1,067,000
Internal Revenue Service (IRS)
       
Income Tax Contingency [Line Items]        
Deferred tax assets, U.S. net operating loss carryforwards 52,000,000      
Stock-based compensation 13,900,000      
Operating loss carryforwards, expiration dates P2026Y      
State jurisdiction
       
Income Tax Contingency [Line Items]        
Deferred tax assets, U.S. net operating loss carryforwards 49,200,000      
Stock-based compensation 13,100,000      
Operating loss carryforwards, expiration dates P2018Y      
Research and Development Expense [Member] | Internal Revenue Service (IRS)
       
Income Tax Contingency [Line Items]        
Tax Credit Carryforward, Amount 6,400,000      
Tax Credit Carryforward, Expiration Date Dec. 31, 2025      
Research and Development Expense [Member] | State jurisdiction
       
Income Tax Contingency [Line Items]        
Tax Credit Carryforward, Amount $ 6,900,000