Quarterly report pursuant to Section 13 or 15(d)

Supplemental disclosures (Details)

v3.7.0.1
Supplemental disclosures (Details) - USD ($)
shares in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Mar. 31, 2017
Mar. 31, 2016
Sep. 30, 2016
Sep. 30, 2015
Aug. 31, 2015
Income Taxes Paid, Net [Abstract]              
Income taxes paid     $ 38,800,000 $ 68,600,000      
Cash and Cash Equivalents [Abstract]              
Cash and cash equivalents $ 94,862,000 $ 60,783,000 94,862,000 60,783,000 $ 66,199,000 $ 74,672,000  
Foreign currency translation adjustments 5,623,000 $ (466,000) (4,071,000) (2,625,000)      
Payments for Repurchase of Equity [Abstract]              
Stock repurchase programs, authorized amount             $ 200,000,000
Repurchases of common stock     (28,858,000) $ (29,139,000)      
Amount remaining available for future stock repurchases 109,000,000   109,000,000        
Restructuring Charges [Abstract]              
Restructuring reserve 200,000   $ 200,000        
Restricted Stock Units (RSUs)              
Employee Benefits and Share-based Compensation [Abstract]              
Granted (in shares)     400        
Vesting period     5 years        
Common Stock              
Payments for Repurchase of Equity [Abstract]              
Common shares repurchased     558 543      
Repurchases of common stock     $ (28,900,000) $ (29,100,000)      
Non-U.S.              
Cash and Cash Equivalents [Abstract]              
Cash and cash equivalents 91,500,000   91,500,000        
United Kingdom              
Restructuring Charges [Abstract]              
Restructuring charges     (2,200,000)        
Mutual Fund              
Compensation and Retirement Disclosure [Abstract]              
Investments in mutual funds 13,500,000   $ 13,500,000        
Employee Severance | United Kingdom              
Restructuring Charges [Abstract]              
Restructuring charges (2,000,000)            
Lease termination | United Kingdom              
Restructuring Charges [Abstract]              
Restructuring charges $ (200,000)