Description of Operations and Summary of Significant Accounting Policies - Summary of Select Unaudited Condensed Consolidated Statement of Operations Reflect Adoption of Accounting Standards (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating expenses
Sales and marketing	$ 23,993	$ 19,792	$ 70,695	$ 60,401
Loss from operations	(2,878)	(4,053)	(14,821)	(18,519)
Foreign exchange (loss) gain	(335)	93	(797)	159
Net loss	$ (4,570)	$ (4,112)	$ (17,966)	$ (18,163)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.10)	$ (0.10)	$ (0.41)	$ (0.46)
ASU 2014-09 | As Previously Reported
Operating expenses
Sales and marketing		$ 20,863		$ 60,983
Loss from operations		(5,124)		(19,101)
Foreign exchange (loss) gain		105		173
Net loss		$ (5,171)		$ (18,731)
Net loss per share attributable to common stockholders, basic and diluted		$ (0.13)		$ (0.48)
ASU 2014-09 | Adjustments
Operating expenses
Sales and marketing		$ (1,071)		$ (582)
Loss from operations		1,071		582
Foreign exchange (loss) gain		(12)		(14)
Net loss		$ 1,059		$ 568
Net loss per share attributable to common stockholders, basic and diluted		$ 0.03		$ 0.02