Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation (Details 3)

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Stock-Based Compensation (Details 3) (USD $)
 3 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Additional disclosure    
Stock-based compensation expense $ 687,000 $ 734,000
Stock options
    
Shares    
Outstanding at the beginning of the period (in shares) 12,851,688  
Granted (in shares) 1,085,800  
Forfeited, cancelled or expired (in shares) (60,088)  
Outstanding at the end of the period (in shares) 13,877,400  
Vested and expected to vest (in shares) 13,612,749  
Options exercisable 10,411,613  
Weighted Average Exercise Price    
Outstanding at the beginning of the period (in dollars per share) $ 1.27  
Granted (in dollars per share) $ 1.43  
Forfeited, cancelled or expired (in dollars per share) $ 2.43  
Outstanding at the end of the period (in dollars per share) $ 1.28  
Vested and expected to vest (in dollars per share) $ 1.28  
Exercisable (in dollars per share) $ 1.32  
Weighted Average Remaining Contractual Term (in years)    
Outstanding at the end of the period 5 years 4 months 24 days  
Vested and expected to vest 5 years 3 months 18 days  
Exercisable 4 years 2 months 12 days  
Aggregate Intrinsic Value    
Outstanding at the end of the period 4,902,918  
Vested or expected to vest 4,825,312  
Exercisable 3,622,299  
Additional disclosure    
Stock-based compensation expense 400,000 400,000
Unrecognized compensation cost $ 2,300,000  
Weighted average period for recognizing compensation cost 2 years 9 months 18 days  
Weighted-average assumptions used to calculate estimated fair value of each stock option    
Risk-free interest rates (as a percent) 1.80% 0.90%
Expected lives (in years) 5 years 8 months 12 days 5 years 8 months 12 days
Expected volatility (as a percent) 77.00% 77.30%
Weighted average grant date fair value of options granted during the period (in dollars per share) $ 0.94 $ 0.60