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Post Retirement Benefits - Multiemployer Plans (Details)
 12 Months Ended
Aug. 10, 2019
$ / h
Aug. 05, 2018
$ / h
Aug. 06, 2017
$ / h
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Multiemployer plans:            
Certified zone status, percent funded limit for red status       65.00%    
Certified zone status, percent funded limit for yellow status       80.00%    
Certified zone status, percent funded limit for green status       80.00%    
Multi-employer plan contributions | $ [1]       $ 710,000 $ 863,000 $ 719,000
Multiemployer plan, postretirement benefit            
Multiemployer plans:            
Maximum percentage of total contribution       5.00%    
Multiemployer plans, collective-bargaining arrangement, maximum hours of work per week for employer contribution       40 hours    
Forecast | Multiemployer plan, postretirement benefit            
Multiemployer plans:            
Multiemployer plans, collective-bargaining arrangement, rate of employer contribution | $ / h 1.55 1.50 1.45      
[1] The plan re-certified its zone status after using the amortization provisions of the Code. The Company's contributions to the plan did not represent more than 5% of total contributions to the plan as indicated in the plan's most recently available annual report for the plan year ended December 31, 2015. Under the terms of the collective-bargaining agreement, the Company is required to make contributions to the plan for each hour worked up to a maximum of 40 hours per person, per week, at the following rates: $1.45 per hour from August 8, 2016 through August 6, 2017; $1.50 per hour from August 7, 2017 through August 5, 2018; $1.55 per hour from August 6, 2018 through August 10, 2019.