Quarterly report pursuant to Section 13 or 15(d)

Supplemental disclosures (Details)

v3.10.0.1
Supplemental disclosures (Details) - USD ($)
 1 Months Ended 3 Months Ended
Feb. 07, 2019
Dec. 31, 2018
Dec. 31, 2017
Sep. 30, 2018
Payments for Repurchase of Equity [Abstract]        
Repurchases of common stock   $ 41,330,000 $ 1,038,000  
Line of Credit Facility [Abstract]        
Long-term debt   120,321,000   $ 374,000
Loss Contingency, Information about Litigation Matters [Abstract]        
Loss contingency, maximum potential loss   31,000,000    
Line of Credit        
Line of Credit Facility [Abstract]        
Long-term debt   120,000,000    
Credit Agreement Expiring 2022        
Debt Instrument, Periodic Payment [Abstract]        
Interest paid   200,000 $ 100,000  
Mutual Fund        
Retirement Benefits [Abstract]        
Investments in mutual funds   $ 18,000,000    
Restricted Stock Units (RSUs)        
Employee Benefits and Share-based Compensation, Noncash [Abstract]        
Granted (in shares)   330,000    
Vesting period   5 years    
Common Stock        
Payments for Repurchase of Equity [Abstract]        
Common shares purchased   654,000 17,000  
Stock Repurchase Program, June 2018        
Payments for Repurchase of Equity [Abstract]        
Stock repurchase programs, authorized amount   $ 200,000,000    
Stock Repurchase Program, June 2018 | Common Stock        
Payments for Repurchase of Equity [Abstract]        
Common shares purchased   (650,000)    
Repurchases of common stock   $ (41,300,000)    
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  
Stock Repurchase Authorized Program, June 2018        
Payments for Repurchase of Equity [Abstract]        
Amount remaining available for future stock repurchases   $ 151,500,000    
Stock Repurchase Authorized Program, June 2018 | Subsequent Event        
Payments for Repurchase of Equity [Abstract]        
Amount remaining available for future stock repurchases $ 147,400,000      
Stock Repurchase Authorized Program, June 2018 | Common Stock | Subsequent Event        
Payments for Repurchase of Equity [Abstract]        
Common shares purchased (61,900)      
Repurchases of common stock $ (4,100,000)