Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accounts Payable and Accrued Liabilities
Retention amounts included in accounts payable	$ 10,100	$ 11,300
Accrued liabilities
Payroll and related employee benefits	85,130	64,705
Current operating lease liability	78,444	74,036
Casualty insurance reserves	9,729	9,918
Corporate income taxes and other taxes	19,736	9,027
Other	29,433	25,815
Total accrued liabilities	$ 222,472	$ 183,501