Annual report pursuant to Section 13 and 15(d)

Equity - Narrative (Details)

v3.8.0.1
Equity - Narrative (Details) - USD ($)
 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Aug. 31, 2015
Stock-based compensation        
Shares available for grants (in shares) 1,500,000      
Compensation expense recognized $ 21,365,000 $ 18,751,000 $ 17,237,000  
Total income tax benefit recognized 15,000,000 7,400,000 7,100,000  
Cash paid to satisfy employees personal tax liability $ 9,175,000 $ 11,614,000 $ 12,451,000  
Stock repurchase programs, authorized amount       $ 200,000,000
Common shares repurchased 600,000 600,000 1,600,000  
Common shares repurchased, cost $ 28,863,000 $ 31,338,000 $ 82,787,000  
Amount remaining available for future stock repurchases 109,900,000      
Restricted stock units (RSU)        
Stock-based compensation        
Compensation expense recognized $ 21,400,000 $ 18,800,000 $ 17,200,000  
Deferred vested award 700,000      
Granted (in dollars per share) $ 53.63 $ 52.00 $ 50.82  
Total fair value $ 24,900,000 $ 27,100,000 $ 68,600,000  
Unrecognized compensation cost $ 37,600,000      
Expected realization period (in years) 5 years      
Weighted average life (in years) 1 year 6 months      
RSUs awarded in 2009 and after | Minimum        
Stock-based compensation        
Award vesting period (in years) 1 year      
RSUs awarded in 2009 and after | Maximum        
Stock-based compensation        
Award vesting period (in years) 5 years      
Stock options        
Stock-based compensation        
Award vesting period (in years) 4 years      
Compensation expense recognized $ 0 $ 0 0  
Award expired period 10 years      
Stock options, exercises in period (in shares) 80,000      
Stock options, outstanding (in shares)   80,000    
Stock options, exercises in period, weighted average exercise price (in dollars per share) $ 11.55      
Cash paid to satisfy employees personal tax liability $ 8,700,000 $ 9,300,000 $ 11,700,000