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Supplemental Retirement Plan and Related Post Retirement Benefits - Summary of the Components of Net Periodic Cost (Details)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
USD ($)
Jul. 01, 2017
USD ($)
Jun. 30, 2018
USD ($)
retirement_plan
Jul. 01, 2017
USD ($)
Retirement Benefits [Abstract]        
Number of non-qualified supplemental retirement defined benefit plans | retirement_plan     2  
SERP        
Defined Benefit Plan Disclosure        
Service Cost $ 50 $ 46 $ 100 $ 92
Interest Cost 225 224 450 448
Amortization of Prior Service Cost 97 97 194 194
Amortization of Net Actuarial Losses 157 93 314 186
Net Periodic Cost 529 460 1,058 920
SERP | SERP Medical        
Defined Benefit Plan Disclosure        
Service Cost 4 2 8 4
Interest Cost 12 10 23 20
Amortization of Prior Service Cost 4 5 8 8
Amortization of Net Actuarial Losses 15 6 29 15
Net Periodic Cost $ 35 $ 23 $ 68 $ 47