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 3 Months Ended 0 Months Ended 3 Months Ended
Apr. 30, 2013
Apr. 30, 2012
Apr. 30, 2013
Stock Options
Apr. 30, 2012
Stock Options
Jan. 31, 2013
Stock Options
Apr. 30, 2013
Stock Options
Black-Scholes option pricing model
Apr. 30, 2012
Stock Options
Black-Scholes option pricing model
Apr. 30, 2013
Stock option with market and service conditions
Jul. 06, 2013
Stock option with market and service conditions
Mr. Joseph Kennedy
Mar. 22, 2012
Stock option with market and service conditions
Mr. Joseph Kennedy
Apr. 30, 2013
Stock option with market and service conditions
Mr. Joseph Kennedy
Monte-Carlo simulation option pricing model
Apr. 30, 2013
Restricted stock units
Apr. 30, 2013
Stock option without a market condition
Apr. 30, 2013
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 increase in number of shares available for grant                           3.00%
Vesting term                 4 years     4 years    
Assumptions used to calculate per-share fair value of stock option at the date of grant                            
Expected life           6 years 3 months 14 days 6 years 8 months 1 day       10 years      
Risk-free interest rate (as a percent)           1.18% 1.52%       2.33%      
Expected volatility (as a percent)           58.00% 57.00%       70.00%      
Expected dividend yield (as a percent)           0.00% 0.00%              
Stock price (in dollars per share)                     $ 10.63      
Options Outstanding Stock Options                            
Balance at the beginning of the period (in shares)     26,102,949                      
Granted (in shares)     1,365,000             800,000        
Exercised (in shares)     (1,573,269)                      
Cancelled (in shares)     (210,962)                      
Balance at the end of the period (in shares)     25,683,718                      
Weighted-Average Exercise Price                            
Balance at the beginning of the period (in dollars per share)     $ 3.22                      
Granted (in dollars per share)     $ 11.49                      
Exercised (in dollars per share)     $ 2.24                      
Cancelled (in dollars per share)     $ 7.82                      
Balance at the end of the period (in dollars per share)     $ 3.68                      
Aggregate Intrinsic Value                            
Aggregate intrinsic value     $ 266,196,000   $ 224,736,000                  
Additional disclosure, stock options                            
Equity awards available for grant at the end of the period (in shares)     12,812,657                      
Stock-based compensation expense 7,381,000 5,500,000                   5,800,000    
Compensation cost not yet recognized                       93,700,000    
Period over which unrecognized compensation expense is expected to be recognized     2 years 4 months 24 days                 3 years 3 months 22 days    
Number of Shares                            
Unvested at the beginning of the period (in shares)                       5,511,709    
Granted (in shares)                       3,958,634    
Vested (in shares)                       (387,490)    
Cancelled (in shares)                       (134,015)    
Unvested at the end of the period (in shares)                       8,948,838    
Weighted-Average Grant-Date Fair Value                            
Unvested at the beginning of the period (in dollars per share)                       $ 10.57    
Granted (in dollars per share)                       $ 12.46    
Vested (in dollars per share)                       $ 11.72    
Cancelled (in dollars per share)                       $ 11.21    
Unvested at the end of the period (in dollars per share)                       $ 11.35    
Unrecognized compensation cost     29,700,000                      
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)     $ 6.31 $ 6.02             $ 6.08      
Lower stock-based compensation expense               1,400,000         300,000  
Stock-based Compensation Expenses                            
Aggregate intrinsic value of options exercised     17,700,000 32,400,000                    
Fair value of options vested     $ 2,200,000 $ 3,400,000