Annual report pursuant to Section 13 and 15(d)

Retirement and Long-Term Incentive Plans - Narrative (Details)

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Retirement and Long-Term Incentive Plans - Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Employer discretionary contribution $ 0 $ 0 $ 700,000
Available shares for future issuance (in shares) 527,357    
Share-based compensation cost charged against income $ 2,795,000 2,741,000 3,125,000
Total unrecognized compensation costs 3,400,000    
Total income tax (expense) benefit under share-base compensation $ (19,000) $ (300,000) 0
Recognition of compensation cost, weighted average period 2 years    
Value of awards granted $ 4,900,000    
Total fair value of shares vested $ 2,700,000    
Non-employee directors      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock vesting period 6 months    
Employee Stock Option | Long Term Incentive Plan 1997      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 1,000,000    
Employee Stock Option | Long Term Incentive Plan 2002      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 500,000    
Employee Stock Option | Long Term Incentive Plan 2011      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 500,000    
Employee Stock Option | Long Term Incentive Plan 2015      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares authorized (in shares) 1,000,000    
Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock vesting period 3 years    
Performance Shares      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance period awards are earned   3 years  
Performance based share compensation expense $ 1,100,000 $ 1,500,000 1,300,000
Fair value of performance based shares granted $ 3,800,000 $ 4,700,000 $ 1,600,000