Accounts Payable, Accrued Expenses and Other Liabilities - Components of Current Portion of Accounts Payable, Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts Payable Accrued Expenses And Other Liabilities Current [Abstract]
Accounts payable and accrued expenses	$ 85,571	$ 79,376
Payroll taxes payable	20,416	12,673
Outside broker payable	41,242	23,361
Contingent consideration	7,116	6,504
Derivative liability	11,401	3,047
Current portion of accounts payable, accrued expenses and other liabilities	$ 165,746	$ 124,961