Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v2.4.0.8
Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2014
Warrant Liabilities [Member]
Mar. 31, 2013
Warrant Liabilities [Member]
Mar. 31, 2014
Warrant Liabilities [Member]
Minimum [Member]
Dec. 31, 2013
Warrant Liabilities [Member]
Minimum [Member]
Mar. 31, 2014
Warrant Liabilities [Member]
Maximum [Member]
Dec. 31, 2013
Warrant Liabilities [Member]
Maximum [Member]
Mar. 31, 2014
Recurring [Member]
Dec. 31, 2013
Recurring [Member]
Mar. 31, 2014
Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Dec. 31, 2013
Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Mar. 31, 2014
Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Dec. 31, 2013
Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
Mar. 31, 2014
Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Dec. 31, 2013
Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
Assets:                            
Money market funds             $ 63,561 [1] $ 82,759 [1] $ 63,561 [1] $ 82,759 [1] $ 0 [1] $ 0 [1] $ 0 [1] $ 0 [1]
U.S. treasury securities             19,996 19,990 19,996 19,990 0 0 0 0
Foreign exchange options             239 361 0 0 239 361 0 0
Total             83,796 103,110 83,557 102,749 239 361 0 0
Liabilities:                            
Contingent warrant liabilities             47,342 69,869 0 0 0 0 47,342 69,869
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]                            
Expected volatility (in hundredths)     74.20% 66.10% 88.40% 86.60%                
Risk-free interest rate (in hundredths)     0.10% 0.10% 0.90% 0.80%                
Expected term     0 years 8 months 12 days 0 years 10 months 24 days 2 years 10 months 24 days 3 years 2 months 12 days                
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]                            
Balance, beginning of period 69,869                          
Reclassification of contingent warrant liability to equity upon exercise of warrants (2,525)                          
Net increase in fair value of contingent warrant liabilities upon revaluation (20,002) 12,800                        
Balance, end of period $ 47,342                          
[1] Included in cash and cash equivalents