CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue	$ 64,213	$ 56,493	$ 184,114	$ 161,486
Costs and expenses
Cost of revenue	15,689	14,541	45,679	43,456
Sales and marketing	26,748	21,603	76,271	66,695
General and administrative	11,972	10,398	33,594	30,528
Product development	13,484	9,726	40,955	29,011
Restructuring costs	722	0	2,806	2,315
Amortization of purchased intangibles	424	470	1,272	1,412
Total costs and expenses	69,039	56,738	200,577	173,417
Loss from operations	(4,826)	(245)	(16,463)	(11,931)
Other (expense) income , net	(213)	191	(53)	412
Loss before provision for income taxes	(5,039)	(54)	(16,516)	(11,519)
Provision for income taxes	2,004	1,256	2,051	3,000
Net loss	$ (7,043)	$ (1,310)	$ (18,567)	$ (14,519)
Net loss per share of common stock:
Basic net loss per common share (in dollars per share)	$ (0.12)	$ (0.02)	$ (0.32)	$ (0.26)
Diluted net loss per common share (in dollars per share)	$ (0.12)	$ (0.02)	$ (0.32)	$ (0.26)
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)	60,014,246	56,524,990	58,667,289	56,153,428
Weighted average shares outstanding used in diluted net loss per common share calculation (in shares)	60,014,246	56,524,990	58,667,289	56,153,428
Cost of revenue
Additional Information on Operating Expenses
Stock-based compensation expense	$ 220	$ 108	$ 604	$ 301
Depreciation expense	1,934	1,715	5,781	5,350
Amortization of purchased intangibles	285	639	859	2,556
Sales and marketing
Additional Information on Operating Expenses
Stock-based compensation expense	1,472	576	3,731	1,984
Depreciation expense	388	417	1,115	1,206
General and administrative
Additional Information on Operating Expenses
Stock-based compensation expense	1,368	622	3,390	2,058
Depreciation expense	275	321	795	911
Product development
Additional Information on Operating Expenses
Stock-based compensation expense	1,014	537	2,613	1,760
Depreciation expense	$ 960	$ 726	$ 2,652	$ 1,550