Basis of Presentation and Summary of Significant Accounting Policies - Fair Value, Financial Assets, Recurring (Details) (Fair Value, Measurements, Recurring [Member], USD $)
In Thousands, unless otherwise specified
Sep. 30, 2012
Dec. 31, 2011
Fair Value, Inputs, Level 1 [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets at fair value $ 29,126 $ 54,701
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 29,126 [1] 54,701 [1]
Fair Value, Inputs, Level 2 [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets at fair value 7,939 15,447
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 7,939 [1] 15,447 [1]
Fair Value, Inputs, Level 3 [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets at fair value 0 0
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 0 [1] 0 [1]
Estimate of Fair Value, Fair Value Disclosure [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets at fair value 37,065 70,148
Estimate of Fair Value, Fair Value Disclosure [Member] | Money Market Funds [Member]
   
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents $ 37,065 [1] $ 70,148 [1]
[1] Comprises money market funds which are included in Cash and cash equivalents in the accompanying balance sheet