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Stock-Based Compensation (Details 3) (USD $)
 3 Months Ended 9 Months Ended 0 Months Ended 1 Months Ended 9 Months Ended
Sep. 30, 2012
Options
Sep. 30, 2011
Options
Sep. 30, 2012
Options
Sep. 30, 2011
Options
Aug. 30, 2012
ESPP
Feb. 29, 2012
ESPP
Jun. 30, 2010
ESPP
item
Sep. 30, 2012
ESPP
Stock-Based Compensation                
Outstanding options fully vested and expected to vest (in shares) 9,900,000   9,900,000          
Remaining contractual life of options fully vested and expected to vest     3 years 8 months 19 days          
Weighted average exercise price of options fully vested and expected to vest (in dollars per share) $ 4.13   $ 4.13          
Aggregate intrinsic value of options fully vested and expected to vest (in dollars) $ 6,000,000   $ 6,000,000          
Fair value of shares vested (in dollars)     1,700,000 1,200,000        
Total intrinsic value of awards exercised (in dollars)     2,300,000 2,200,000        
Awards exercisable (in shares) 6,200,000 5,800,000 6,200,000 5,800,000        
Weighted average exercise price of awards exercisable (in dollars per share) $ 4.43 $ 4.36 $ 4.43 $ 4.36        
Assumptions used in estimation of fair value of the share-based payment awards on the grant date                
Risk-free interest rate, minimum (as a percent) 0.20% 0.20% 0.20% 0.20%        
Risk-free interest rate, maximum (as a percent) 0.60% 0.70% 0.80% 1.70%        
Volatility, minimum (as a percent) 65.20% 40.70% 65.20% 40.70%        
Volatility, maximum (as a percent) 73.10% 61.30% 73.10% 63.80%        
Expected life 4 years 4 years 4 years 4 years        
Dividend yield (as a percent) 0.00% 0.00% 0.00% 0.00%        
Period for which historical volatility is considered to determine expected volatility     4 years          
Employee Stock Purchase Plan                
Shares of common stock reserved for issuance             2,000,000  
Maximum amount of shares that eligible employee may purchase annually (in dollars)             25,000  
Number of offering periods             2  
Offering period               6 months
Purchase price to be paid by participants as percentage of price per share either at the beginning or the end of each six-month offering period, whichever is less             85.00%  
Shares of common stock issued under the plan         173,000 178,000    
Aggregate purchase price (in dollars)         $ 501,000 $ 579,000    
Shares authorized and unissued               1,335,000