XML 53 R32.htm IDEA: XBRL DOCUMENT v3.20.1
Pension Plans - Multi-employer (Details) - Multi-employer defined benefit pension plan - USD ($)
$ in Thousands
1 Months Ended 3 Months Ended 12 Months Ended
Jun. 30, 2012
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Pension Plans            
Insolvent period   20 years        
Estimated liability upon withdrawal from plan       $ 99,800 $ 81,600 $ 82,200
Percentage of annual compounded surcharge for rehabilitation   5.00%        
Percentage of interim surcharge 5.00%          
Pension expense   $ 685 $ 574 2,961 2,836  
Surcharges   $ 241 $ 184 $ 948 $ 811