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Postretirement Benefit Plans (Details)
 5 Months Ended 6 Months Ended 12 Months Ended
May 31, 2018
USD ($)
Nov. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
employees
May 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
employees
May 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
employees
Multiemployer Defined Contributory Trust Plan [Member]              
Multiemployer Plans [Line Items]              
Number of employees in plan | employees     735   1,215   1,221
Required employer's contribution per hour per active employee     $ 0.90   $ 0.90   $ 0.85
Required defined contributory trust contribution, percent of earnings.     4.50%   4.50%   4.50%
Period Contributions     $ 2,400,000   $ 2,600,000   $ 2,800,000
Multiemployer Health and Welfare Plan [Member]              
Multiemployer Plans [Line Items]              
Number of employees in plan | employees         475   604
Required employer's contribution per hour per active employee $ 6.10 $ 7.00   $ 6.70   $ 6.40  
Period Contributions     $ 5,800,000   $ 6,700,000   $ 7,700,000