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Significant Accounting Policies (Details 6) (USD $)
9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Employee Stock Options:
   
Weighted-average assumptions    
Risk-free interest rate (as a percent) 1.00% 2.30%
Dividend yield (as a percent) 0.00% 0.00%
Volatility (as a percent) 50.65% 52.40%
Expected Life 5 years 1 month 6 days 5 years 3 months 18 days
ESPP:
   
Weighted-average assumptions    
Risk-free interest rate (as a percent) 0.20% 0.10%
Dividend yield (as a percent) 0.00% 0.00%
Volatility (as a percent) 49.60% 34.90%
Expected Life 6 months 6 months
Board of Director Stock Options:
   
Weighted-average assumptions    
Risk-free interest rate (as a percent) 1.30% 2.90%
Dividend yield (as a percent) 0.00% 0.00%
Volatility (as a percent) 51.30% 52.80%
Expected Life 7 years 7 months 6 days 7 years 9 months 18 days
RSUs | Board of Directors
   
Weighted-average assumptions    
Weighted-average grant date fair value (in dollars per unit) 7.97  
RSUs | Employees
   
Weighted-average assumptions    
Weighted-average grant date fair value (in dollars per unit) 12.94