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Employee Benefit Plans (Details)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2018
USD ($)
plan
Jul. 01, 2017
USD ($)
Jun. 30, 2018
USD ($)
plan
Jul. 01, 2017
USD ($)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]        
Amount Company expects to contribute to its pension plans $ 4,800   $ 4,800  
Payment for pension benefits     $ 1,500 $ 1,600
Multiemployer Plans [Abstract]        
Number Of Multiemployer Plans, Withdrawal Obligation Could Be Material | plan 2   2  
Number Of Multiemployer Plans Withdrawal Obligation Could Be Material Certified Red Zone | plan 1   1  
Number of Multiemployer Plans, Certified Red Zone | plan 6   6  
Number of Multiemployer Plans, Certified Yellow Zone | plan 1   1  
Number Of Multiemployer Plans, Withdrawal Obligation | plan 2   2  
Accrued liability representing the present value of scheduled withdrawal liability payments for under-funded multi-employer plan $ 1,700   $ 1,700  
Maximum [Member]        
Multiemployer Plans [Abstract]        
Multiemployer Plan, Contributions To Individual Plan, Percent     5.00%  
Pension Plan, Defined Benefit [Member]        
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]        
Service cost 779 $ 750 $ 1,578 1,485
Interest cost 1,616 1,679 3,241 3,348
Expected return on plan assets (2,059) (1,790) (4,123) (3,578)
Amortization of prior service cost 8 9 17 18
Amortization of net loss 888 1,203 1,776 2,406
Net pension cost $ 1,232 $ 1,851 $ 2,489 $ 3,679