Quarterly report pursuant to Section 13 or 15(d)

Supplemental disclosures (Details)

v3.4.0.3
Supplemental disclosures (Details) - USD ($)
 3 Months Ended 6 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Mar. 31, 2016
Mar. 31, 2015
Sep. 30, 2015
Aug. 31, 2015
Sep. 30, 2014
Income Taxes Paid, Net [Abstract]              
Income taxes paid     $ 68,600,000 $ 37,600,000      
Cash and Cash Equivalents [Abstract]              
Cash and cash equivalents $ 60,783,000 $ 114,535,000 60,783,000 114,535,000 $ 74,672,000   $ 158,112,000
Foreign currency translation adjustments (466,000) $ (10,553,000) (2,625,000) (21,033,000)      
Effect of exchange rate changes on cash and cash equivalents     1,064,000 5,937,000      
Decline in goodwill value     1,754,000        
Payments for Repurchase of Equity [Abstract]              
Stock repurchase programs, authorized amount           $ 200,000,000  
Repurchases of common stock     (29,139,000) $ (30,618,000)      
Amount remaining available for future stock repurchases 139,400,000.0   139,400,000.0        
Compensation and Retirement Disclosure [Abstract]              
Investments in mutual funds 21,519,000   $ 21,519,000   $ 19,310,000    
Restricted Stock Units (RSUs)              
Employee Benefits and Share-based Compensation [Abstract]              
Granted (in shares)     467,000.000        
Vesting period     5 years        
Common Stock              
Payments for Repurchase of Equity [Abstract]              
Common shares repurchased     543,000 753,000      
Non-U.S.              
Cash and Cash Equivalents [Abstract]              
Cash and cash equivalents 47,000,000   $ 47,000,000        
Portion at Fair Value Measurement              
Compensation and Retirement Disclosure [Abstract]              
Investments in mutual funds $ 10,600,000   $ 10,600,000