Annual report pursuant to Section 13 and 15(d)

Stock compensation (Details)

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Stock compensation (Details) (USD $)
1 Months Ended 12 Months Ended
Jun. 30, 2013
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2011
Stock-based compensation        
Stock split 2      
Shares available for grants   2,800,000    
Information pertaining to stock options vested and exercised        
Total income tax benefit recognized   $ 5,200,000 $ 4,300,000 $ 3,700,000
Cash paid to satisfy employees personal tax liability   8,868,000 4,464,000 3,516,000
RSUs
       
Stock-based compensation        
Compensation expense recognized   14,600,000 12,100,000 9,400,000
Summary of RSU activity        
Non-vested shares outstanding at the beginning of the period   2,892,140    
Granted (in shares)   566,249    
Vested (in shares)   (931,993)    
Forfeited (in shares)   (107,442)    
Non-vested shares outstanding at the end of the period   2,418,954 2,892,140  
Weighted-Average Grant-Date Fair value        
Non-vested shares outstanding at the beginning of the period (in dollars per share)   $ 13.86    
Granted (in dollars per share)   $ 30.66 $ 21.00 $ 15.90
Vested (in dollars per share)   $ 14.46    
Forfeited (in dollars per share)   $ 15.88    
Non-vested shares outstanding at the end of the period (in dollars per share)   $ 17.47 $ 13.86  
Total fair value   40,800,000 25,000,000 14,500,000
Total unrecognized compensation cost related to unvested RSUs   29,000,000    
Unrecognized compensation cost period expected to be realized   5 years    
Weighted Average Exercise Price        
Weighted average remaining life   1 year 7 months 6 days    
Information pertaining to stock options vested and exercised        
Cash paid to satisfy employees personal tax liability   8,900,000 4,500,000 3,500,000
RSUs awarded before 2009
       
Stock-based compensation        
Award vesting period   6 years    
RSUs awarded in 2009 and after
       
Stock-based compensation        
Award vesting period   5 years    
Stock options
       
Stock-based compensation        
Award vesting period   4 years    
Award expired period   10 years    
Summary of stock option activity        
Outstanding at the beginning of the period (in shares)   720,358    
Exercised (in shares)   (288,742)    
Forfeited or expired (in shares)   (10,152)    
Outstanding and exercisable at the end of the period (in shares)   421,464 720,358  
Weighted Average Exercise Price        
Outstanding at the beginning of the period (in dollars per share)   $ 8.26    
Exercised (in dollars per share)   $ 7.50    
Forfeited or expired (in dollars per share)   $ 5.54    
Outstanding and exercisable at the end of the period (in dollars per share)   $ 8.85 $ 8.26  
Intrinsic value of outstanding and exercisable stock options at the end of the period   15,300,000    
Weighted average remaining life   2 years 3 months 18 days    
Information pertaining to stock options vested and exercised        
Aggregate intrinsic value of all stock options exercised   7,081,000 10,920,000 15,102,000
Net cash proceeds from exercise of stock options   $ 2,168,000 $ 6,441,000 $ 12,496,000