Quarterly report pursuant to Section 13 or 15(d)

Supplemental Retirement Plan and Related Post Retirement Benefits - Summary of the Components of Net Periodic Cost (Details)

v3.8.0.1
Supplemental Retirement Plan and Related Post Retirement Benefits - Summary of the Components of Net Periodic Cost (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2018
USD ($)
retirement_plan
Apr. 01, 2017
USD ($)
Retirement Benefits [Abstract]    
Number of non-qualified supplemental retirement defined benefit plans | retirement_plan 2  
SERP    
Defined Benefit Plan Disclosure    
Service Cost $ 50 $ 46
Interest Cost 225 224
Amortization of Prior Service Cost 97 97
Amortization of Net Actuarial Losses 157 93
Net Periodic Cost 529 460
SERP | SERP Medical    
Defined Benefit Plan Disclosure    
Service Cost 4 2
Interest Cost 11 10
Amortization of Prior Service Cost 4 4
Amortization of Net Actuarial Losses 15 8
Net Periodic Cost $ 34 $ 24