Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Details)

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Fair Value Measurements (Details) (USD $)
Dec. 31, 2012
Nov. 03, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Business Acquisition, Contingent Consideration, at Fair Value   $ 1,600,000
Assets, Fair Value Disclosure, Nonrecurring 2,523,000  
Goodwill, Fair Value Disclosure 2,523,000  
Carrying (Reported) Amount, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 52,783,000  
Investments, Fair Value Disclosure 3,812,000  
Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 52,783,000  
Investments, Fair Value Disclosure 3,812,000  
Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 52,783,000  
Investments, Fair Value Disclosure 3,812,000  
Money Market Funds [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 48,000  
Money Market Funds [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 48,000  
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 48,000  
Mutual Funds [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 44,000  
Mutual Funds [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 44,000  
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 44,000  
US Treasury Securities [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 2,450,000  
US Treasury Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 2,450,000  
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 2,450,000  
Government agency securities [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 1,270,000  
Government agency securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 1,270,000  
Government agency securities [Member] | Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Investments, Fair Value Disclosure 1,270,000  
Cash [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 10,956,000  
Cash [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 10,956,000  
Cash [Member] | Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 10,956,000  
Money Market Funds [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 41,827,000  
Money Market Funds [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure 41,827,000  
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Cash and Cash Equivalents, Fair Value Disclosure $ 41,827,000