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Significant Accounting Policies (Details 2) (USD $)
6 Months Ended 6 Months Ended
Jun. 30, 2011
Dec. 31, 2010
Jun. 30, 2011
Patents
Jun. 30, 2010
Patents
Short-term investments        
Maximum remaining maturity period at time of purchase of liquid investments classified as cash equivalents (in days) 90      
Initial remaining maturity period at time of purchase of liquid investments classified as short-term investments, greater than (in days) 90      
Entity's cost method equity investments ownership percentage, less than (as a percent) 20.00%      
Inventory valuation        
Raw materials $ 2,249,000 $ 2,484,000    
Patents        
Estimated useful life (in years)     10  
Write-off of patent costs to estimated net realizable values     $ 801,000 $ 385,000