Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation Plans and Awards (Details)

v2.4.0.6
Stock-based Compensation Plans and Awards (Details) (USD $)
3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 1 Months Ended 9 Months Ended
Oct. 31, 2012
Oct. 31, 2011
Oct. 31, 2012
Oct. 31, 2011
Oct. 31, 2012
Stock Options
Oct. 31, 2011
Stock Options
Oct. 31, 2012
Stock Options
Oct. 31, 2011
Stock Options
Jan. 31, 2012
Stock Options
Oct. 31, 2011
Stock Options
Black-Scholes option pricing model
Oct. 31, 2012
Stock Options
Black-Scholes option pricing model
Oct. 31, 2011
Stock Options
Black-Scholes option pricing model
Oct. 31, 2011
Stock Options
Minimum
Black-Scholes option pricing model
Oct. 31, 2011
Stock Options
Minimum
Black-Scholes option pricing model
Oct. 31, 2011
Stock Options
Maximum
Black-Scholes option pricing model
Oct. 31, 2011
Stock Options
Maximum
Black-Scholes option pricing model
Oct. 31, 2012
Restricted stock units
Oct. 31, 2012
Restricted stock units
Mar. 31, 2012
Non-statutory stock options
Mr. Joseph Kennedy
Oct. 31, 2012
Non-statutory stock options
Mr. Joseph Kennedy
Oct. 31, 2012
Non-statutory stock options
Mr. Joseph Kennedy
Monte-Carlo simulation option pricing model
Oct. 31, 2012
Non-statutory stock options
Minimum
Mr. Joseph Kennedy
Oct. 31, 2012
2011 Plan
Stock-based Compensation Plans and Awards                                              
Annual fixed increase alternative, increase in shares of common stock reserved for issuance                                             10,000,000
Annual percentage increase alternative, increase in common stock reserved for issuance as a percentage of common stock outstanding                                             4.00%
Percentage of outstanding shares of common stock added to the number of shares in the reserve                                             4.00%
Assumptions used to calculate per-share fair value of stock option at the date of grant                                              
Expected life                     6 years 8 months 1 day   5 years 9 months 29 days 5 years 8 months 19 days 6 years 25 days 7 years 7 days         10 years    
Risk-free interest rate, minimum (as a percent)                   1.19%   1.19%                      
Risk-free interest rate, maximum (as a percent)                   1.27%   2.77%                      
Risk-free interest rate (as a percent)                     1.52%                   2.33%    
Expected volatility, minimum (as a percent)                   54.00%   54.00%                      
Expected volatility, maximum (as a percent)                   55.00%   57.00%                      
Expected volatility (as a percent)                     57.00%                   70.00%    
Stock price (in dollars per share)                                         $ 10.63    
Options Outstanding Stock Options                                              
Balance at the beginning of the period (in shares)             34,810,926                                
Granted (in shares)             1,350,000                       800,000        
Exercised (in shares)             (5,992,401)                                
Cancelled (in shares)             (1,152,360)                                
Balance at the end of the period (in shares)         29,016,165   29,016,165                                
Weighted-Average Exercise Price                                              
Balance at the beginning of the period (in dollars per share)             $ 2.43                                
Granted (in dollars per share)             $ 10.63                                
Exercised (in dollars per share)             $ 0.85                                
Cancelled (in dollars per share)             $ 5.62                                
Balance at the end of the period (in dollars per share)         $ 3.02   $ 3.02                                
Aggregate Intrinsic Value                                              
Aggregate intrinsic value (in dollars)         $ 179,321,000   $ 179,321,000   $ 379,355,000                            
Additional disclosure, stock options                                              
Equity awards available for grant at the end of the period (in shares)         13,511,565   13,511,565                                
Vesting period                                   4 years   4 years      
Stock-based compensation expense 7,073,000 2,675,000 18,610,000 5,739,000                         2,900,000 7,000,000          
Total compensation cost not yet recognized related to non-vested RSUs                                 42,900,000 42,900,000          
Period over which unrecognized compensation expense is expected to be recognized             2 years 4 months 24 days                     3 years 3 months 29 days     4 years 8 months 12 days    
Number of Shares                                              
Unvested at the beginning of the period (in shares)                                   1,426,975          
Granted (in shares)                                   3,286,500          
Vested (in shares)                                   (229,425)          
Cancelled (in shares)                                   (193,862)          
Unvested at the end of the period (in shares)                                 4,290,188 4,290,188          
Weighted-Average Grant-Date Fair Value                                              
Unvested at the beginning of the period (in dollars per share)                                   $ 12.03          
Granted (in dollars per share)                                   $ 11.03          
Vested (in dollars per share)                                   $ 12.24          
Cancelled (in dollars per share)                                   $ 12.29          
Unvested at the end of the period (in dollars per share)                                 $ 11.24 $ 11.24          
Period of time that the trailing weighted average stock price must exceed a certain price for the stock award to vest, prior to July 6, 2017                                       60 days      
Share price, under a sale of the entity, that must be obtained for the stock award to vest prior to July, 6, 2017 (in dollars per share)                                           $ 21.00  
Share price that must be obtained for the stock award to vest prior to July, 6, 2017 (in dollars per share)                                           $ 21.00  
Weighted-average fair value of stock option granted (in dollars per share)           $ 6.02 $ 6.02 $ 4.55                         $ 6.08    
Total compensation cost related to stock options granted, but not yet recognized                                         34,600,000    
Total grant date fair value of stock options vested         2,600,000 1,300,000 10,600,000 3,100,000                              
Aggregate intrinsic value         $ 11,900,000 $ 3,000,000 $ 63,500,000 $ 34,300,000