Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Payroll and related employee benefits	$ 68,210	$ 53,802
Accrued insurance	39,946	44,471
Performance guarantees (see Note 1)	88,606	83,110
Other	39,645	37,204
Total	$ 236,407	$ 218,587