Annual report pursuant to Section 13 and 15(d)

Employee Retirement Plans - Multiemployer plans (Details)

v3.20.4
Employee Retirement Plans - Multiemployer plans (Details) - NCT - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Employee Retirement Plans      
Contribution to NCT (as a percent of total plan contribution) 1.00%    
Contributions by employer $ 2,710 $ 3,810 $ 3,319