Quarterly report pursuant to Section 13 or 15(d)

Supplemental disclosures (Details)

v3.19.1
Supplemental disclosures (Details) - USD ($)
3 Months Ended 6 Months Ended
Mar. 31, 2019
Mar. 31, 2019
Mar. 31, 2018
Sep. 30, 2018
Payments for Repurchase of Equity [Abstract]        
Repurchases of common stock $ 4,084,000 $ 45,414,000 $ 1,038,000  
Line of Credit Facility [Abstract]        
Long-term debt 75,295,000 75,295,000   $ 374,000
Loss Contingency, Information about Litigation Matters [Abstract]        
Loss contingency, maximum potential loss 31,000,000.0 31,000,000.0    
Line of Credit        
Line of Credit Facility [Abstract]        
Long-term debt 75,000,000.0 75,000,000.0    
Credit Agreement Expiring 2022        
Debt Instrument, Periodic Payment [Abstract]        
Interest paid   1,800,000 $ 100,000  
Mutual Fund        
Retirement Benefits [Abstract]        
Investments in mutual funds $ 20,000,000.0 $ 20,000,000.0    
Restricted Stock Units (RSUs)        
Employee Benefits and Share-based Compensation, Noncash [Abstract]        
Granted (in shares)   346,000    
Vesting period   5 years    
Restricted Stock Units (RSUs) | Member of Board of Directors        
Employee Benefits and Share-based Compensation, Noncash [Abstract]        
Vesting period   1 year    
Common Stock        
Payments for Repurchase of Equity [Abstract]        
Common shares purchased 62,000 716,000 17,000  
Stock Repurchase Program, June 2018        
Payments for Repurchase of Equity [Abstract]        
Stock repurchase programs, authorized amount $ 200,000,000 $ 200,000,000    
Stock Repurchase Program, June 2018 | Common Stock        
Payments for Repurchase of Equity [Abstract]        
Common shares purchased   700,000    
Repurchases of common stock   $ (45,400,000)    
Stock Repurchase Program, August 2015 | Common Stock        
Payments for Repurchase of Equity [Abstract]        
Common shares purchased     17,000  
Repurchases of common stock     $ 1,000,000.0  
Stock Repurchase Authorized Program, June 2018        
Payments for Repurchase of Equity [Abstract]        
Amount remaining available for future stock repurchases $ 147,400,000 $ 147,400,000