Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accounts Payable and Accrued Liabilities
Retention amounts included in accounts payable	$ 10,900	$ 11,300
Accrued liabilities
Payroll and related employee benefits	74,008	64,705
Current operating lease liability	79,532	74,036
Casualty insurance reserves	9,902	9,918
Corporate income taxes and other taxes	6,822	9,027
Other	22,384	25,815
Total accrued liabilities	$ 192,648	$ 183,501