Quarterly report pursuant to Section 13 or 15(d)

Stock Award Plans (Details 2)

v2.4.0.6
Stock Award Plans (Details 2) (USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
item
Sep. 30, 2011
Employee Stock Purchase Plan
        
Stock award plans        
Award offering period     24 months  
Number of purchase periods per award offering period     4  
Award purchase period     6 months  
Purchase price expressed as a percentage of fair market value of common stock on the first day of the offering period     85.00%  
Purchase price expressed as a percentage of fair market value of common stock on the purchase date     85.00%  
Weighted-average assumptions relating to options granted        
Risk-free interest rate (as a percent)     0.20% 0.30%
Expected term     1 year 2 months 12 days 1 year
Dividend yield (as a percent)     0.00% 0.00%
Expected volatility (as a percent)     47.30% 61.40%
Additional disclosures        
Shares of common stock available for future grant 604,710   604,710  
Stock options
        
Stock award plans        
Number of homogenous groups for purposes of determining fair values of options     3  
Contractual term of the option       10 years
Weighted-average assumptions relating to options granted        
Risk-free interest rate (as a percent) 0.70% 1.20% 0.90% 2.10%
Expected term 5 years 5 years 5 years 6 months 5 years 2 months 12 days
Dividend yield (as a percent) 0.00% 0.00% 0.00% 0.00%
Expected volatility (as a percent) 83.90% 83.80% 81.60% 84.20%
Additional disclosures        
Options granted (in shares)     2,135,016 2,233,315
Grant-date weighted-average fair value (in dollars per share)     $ 5.44 $ 4.63
Total unrecognized compensation cost, net of estimated forfeitures $ 5.3   $ 5.3  
Shares of common stock available for future grant 3,212,380   3,212,380  
Options exercised during the period (in shares)     248,334