Current Prepaid Expenses - Summary of Current Prepaid Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid technology maintenance costs	$ 2,600	$ 2,000
Deferred deployment costs	1,800	1,900
Prepaid commissions	600	1,100
Prepaid marketing	300	500
Prepaid insurance	200	100
Other	300	200
Total	$ 5,811	$ 5,805