Cash, Cash Equivalents, and Short-Term Investments (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Jun. 30, 2011
Dec. 31, 2010
Cash and cash equivalents:        
Cash and cash equivalents, Amortized Cost $ 59,859 $ 96,025    
Cash and cash equivalents, Gross Unrealized Gains          
Cash and cash equivalents, Gross Unrealized Losses 4      
Cash and cash equivalents, Fair Value 59,855 96,025 [1] 14,511 16,410
Short-term investments:        
Short-term investments, Amortized Cost 40,425      
Short-term investments, Gross Unrealized Gains 6      
Short-term investments, Gross Unrealized Losses 24       
Short-term investments, Estimated Fair Value 40,407 1,587 [1]    
Cash [Member]
        
Cash and cash equivalents:        
Cash and cash equivalents, Amortized Cost 26,141 26,023    
Cash and cash equivalents, Gross Unrealized Gains          
Cash and cash equivalents, Gross Unrealized Losses         
Cash and cash equivalents, Fair Value 26,141 26,023    
Short-term investments:        
Short-term investments, Gross Unrealized Losses         
Mutual funds [Member]
        
Short-term investments:        
Short-term investments, Amortized Cost 367 1,644    
Short-term investments, Gross Unrealized Gains          
Short-term investments, Gross Unrealized Losses 17 57    
Short-term investments, Estimated Fair Value 350 1,587    
US agency securities [Member]
        
Short-term investments:        
Short-term investments, Amortized Cost 3,005      
Short-term investments, Gross Unrealized Gains         
Short-term investments, Gross Unrealized Losses 4      
Short-term investments, Estimated Fair Value 3,001      
Corporate debt obligations [Member]
        
Cash and cash equivalents:        
Cash and cash equivalents, Amortized Cost 1,752      
Cash and cash equivalents, Gross Unrealized Gains         
Cash and cash equivalents, Gross Unrealized Losses 1      
Cash and cash equivalents, Fair Value 1,751      
Short-term investments:        
Short-term investments, Amortized Cost 21,994      
Short-term investments, Gross Unrealized Gains 6      
Short-term investments, Gross Unrealized Losses         
Short-term investments, Estimated Fair Value 22,000      
Bank deposits [Member]
        
Cash and cash equivalents:        
Cash and cash equivalents, Amortized Cost 11,219 20,000    
Cash and cash equivalents, Gross Unrealized Gains          
Cash and cash equivalents, Gross Unrealized Losses         
Cash and cash equivalents, Fair Value 11,219 20,000    
Short-term investments:        
Short-term investments, Amortized Cost 10,063      
Short-term investments, Gross Unrealized Gains         
Short-term investments, Gross Unrealized Losses          
Short-term investments, Estimated Fair Value 10,063      
Commercial paper [Member]
        
Cash and cash equivalents:        
Cash and cash equivalents, Amortized Cost 12,898      
Cash and cash equivalents, Gross Unrealized Gains         
Cash and cash equivalents, Gross Unrealized Losses 3      
Cash and cash equivalents, Fair Value 12,895      
Short-term investments:        
Short-term investments, Amortized Cost 4,996      
Short-term investments, Gross Unrealized Gains         
Short-term investments, Gross Unrealized Losses 3      
Short-term investments, Estimated Fair Value 4,993      
Money market funds [Member]
        
Cash and cash equivalents:        
Cash and cash equivalents, Amortized Cost 7,849 50,002    
Cash and cash equivalents, Gross Unrealized Gains          
Cash and cash equivalents, Gross Unrealized Losses         
Cash and cash equivalents, Fair Value 7,849 50,002    
Short-term investments:        
Short-term investments, Gross Unrealized Losses         
[1] The Condensed Consolidated Balance Sheet as of December 31, 2011 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.