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Pension Plans - Multi-employer (Details) - Multi-employer defined benefit pension plan - USD ($)
$ in Thousands
1 Months Ended 9 Months Ended 12 Months Ended
Jun. 30, 2012
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Dec. 31, 2017
Sep. 29, 2019
Dec. 31, 2016
Multiemployer Plans [Line Items]              
Insolvent period   20 years          
Estimated liability upon withdrawal from plan       $ 81,600 $ 82,200 $ 99,800 $ 72,700
Percentage of annual compounded surcharge for rehabilitation   5.00%          
Percentage of interim surcharge 5.00%            
Pension expense   $ 2,307 $ 2,201 2,836 2,617    
Surcharges   $ 738 $ 630 $ 811 $ 656