Annual report pursuant to Section 13 and 15(d)

Employee Retirement Plans - Expected Benefit Payments (Details)

v3.8.0.1
Employee Retirement Plans - Expected Benefit Payments (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Expected benefit payments    
Voluntary contribution $ 1,500  
Pension plan    
Expected benefit payments    
2018 1,540  
2019 1,460  
2020 1,510  
2021 1,550  
2022 1,720  
2023-2027 10,230  
Pension funding contributions made 1,669 $ 1,711
Required pension funding contributions expected to be made in next fiscal year 72  
Pension plan | Minimum    
Expected benefit payments    
Pension funding contributions made $ 169