Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued subcontractor and other direct costs	$ 47,508	$ 30,153
Deposits	6,641	12,389
Accrued IT and software licensing costs	2,261	5,349
Accrued taxes and insurance premiums	1,963	1,306
Accrued lease exit and facilities costs	1,591	77
Accrued interest	705	841
Accrued professional services	1,131	795
Other accrued expenses and current liabilities	3,280	1,721
Total accrued expenses and other current liabilities	$ 65,080	$ 52,631