Accrued Expenses and Other Liabilities - Components of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of accrued liabilities
Accrued bonuses	$ 5,590	$ 3,053
Accrued payroll related liabilities	3,277	2,614
Accrued vacation	2,497	2,243
Accrued commissions	825	2,537
Accrued software expense	675	844
Accrued contractor fees	346	455
Accrued professional service fees	341	344
Deferred rent	64	74
Income tax related accruals	189	166
Other accrued expenses	1,180	1,167
Total	$ 14,984	$ 13,497