Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Details)

v2.4.0.8
Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Warrant Liabilities [Member]
      
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]      
Expected volatility (in hundredths)   40.00%  
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Balance, beginning of period $ 15,001 $ 379 $ 4,245
Initial fair value of warrants issued in March 2012   6,390  
Reclassification of contingent warrant liability to equity upon exercise of warrants (6,171) (940)  
Net increase (decrease) in fair value of contingent warrant liabilities upon revaluation 61,039 9,172 (3,866)
Balance, end of period 69,869 15,001 379
Warrant Liabilities [Member] | Minimum [Member]
      
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]      
Expected volatility (in hundredths) 66.10%    
Risk-free interest rate (in hundredths) 0.10% 0.30%  
Expected term 0 years 10 months 24 days 1 year 10 months 24 days  
Warrant Liabilities [Member] | Maximum [Member]
      
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]      
Expected volatility (in hundredths) 86.60%    
Risk-free interest rate (in hundredths) 0.80% 0.70%  
Expected term 3 years 2 months 12 days 4 years 2 months 12 days  
Recurring [Member]
      
Assets:      
Money market funds 82,759 [1] 37,461 [1]  
U.S. treasury securities 19,989 39,987  
Foreign exchange options 361 488  
Total 103,109 77,936  
Liabilities:      
Contingent warrant liabilities 69,869 15,001  
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
      
Assets:      
Money market funds 82,759 [1] 37,461 [1]  
U.S. treasury securities 19,989 39,987  
Foreign exchange options 0 0  
Total 102,748 77,448  
Liabilities:      
Contingent warrant liabilities 0 0  
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
      
Assets:      
Money market funds 0 [1] 0 [1]  
U.S. treasury securities 0 0  
Foreign exchange options 361 488  
Total 361 488  
Liabilities:      
Contingent warrant liabilities 0 0  
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
      
Assets:      
Money market funds 0 [1] 0 [1]  
U.S. treasury securities 0 0  
Foreign exchange options 0 0  
Total 0 0  
Liabilities:      
Contingent warrant liabilities $ 69,869 $ 15,001  
[1] Included in cash and cash equivalents