CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue	$ 66,402	$ 58,241
Costs and expenses
Cost of revenue	18,649	13,954
Sales and marketing	33,036	24,131
General and administrative	14,167	10,123
Product development	18,173	13,252
Restructuring costs	279	178
Amortization of purchased intangibles	461	424
Total costs and expenses	84,765	62,062
Loss from operations	(18,363)	(3,821)
Other income , net	66	129
Loss before provision for (benefit from) income taxes	(18,297)	(3,692)
Provision for (benefit from) income taxes	593	(489)
Net loss	$ (18,890)	$ (3,203)
Net loss per share of common stock:
Basic net loss per common share (in dollars per share)	$ (0.31)	$ (0.06)
Diluted net loss per common share (in dollars per share)	$ (0.31)	$ (0.06)
Weighted-average shares used to compute net loss per share:
Weighted average shares outstanding used in basic net loss per common share calculation (in shares)	61,422,227	57,309,707
Weighted average shares outstanding used in diluted net loss per common share calculation (in shares)	61,422,227	57,309,707
Cost of revenue
Additional Information on Operating Expenses
Stock-based compensation expense	$ 620	$ 154
Depreciation expense	2,027	1,916
Amortization of purchased intangibles	285	287
Sales and marketing
Additional Information on Operating Expenses
Stock-based compensation expense	1,599	886
Depreciation expense	357	356
General and administrative
Additional Information on Operating Expenses
Stock-based compensation expense	2,566	840
Depreciation expense	231	246
Product development
Additional Information on Operating Expenses
Stock-based compensation expense	2,381	558
Depreciation expense	$ 1,266	$ 840