Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accounts Payable and Accrued Liabilities
Accounts Payable, Current	$ 134,091	$ 168,110
Retention amounts included in accounts payable	10,700	10,600
Accrued expenses and other current liabilities
Payroll and related employee benefits	45,474	42,718
Insurance, including self-insurance reserves	44,034	42,546
Reserve for estimated losses on uncompleted contracts	13,019	12,801
Corporate income taxes and other taxes	7,623	3,368
Accrued administrative cost	3,515	3,791
Other	2,579	2,782
Total accrued expenses and other current liabilities	$ 116,244	$ 108,006