Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 291,609	$ 249,838	$ 218,876
Costs and expenses:
Cost of revenue	78,878	62,479	58,205
Sales and marketing	156,814	103,344	90,905
General and administrative	56,967	45,873	43,124
Product development	82,145	55,707	40,034
Restructuring costs	2,043	4,468	2,594
Amortization of purchased intangibles	1,794	1,670	1,840
Total costs and expenses	378,641	273,541	236,702
Loss from operations	(87,032)	(23,703)	(17,826)
Other (expense) income, net
Interest (expense) income	(7,407)	22	26
Other income (expense), net	1,213	(493)	110
Total Other (expense) income, net	(6,194)	(471)	136
Loss before provision for income taxes	(93,226)	(24,174)	(17,690)
Provision for income taxes	2,845	858	501
Net loss	$ (96,071)	$ (25,032)	$ (18,191)
Net loss per share of common stock:
Basic (in dollars per share)	$ (1.53)	$ (0.42)	$ (0.32)
Diluted (in dollars per share)	$ (1.53)	$ (0.42)	$ (0.32)
Weighted-average shares used to compute net loss income per share:
Basic (in shares)	62,593,026	59,203,400	56,358,017
Diluted (in shares)	62,593,026	59,203,400	56,358,017
Additional information on costs and expenses:
Stock compensation expense	$ 44,105	$ 14,841	$ 8,944
Depreciation and amortization expense	16,366	14,188	12,358
Cost of revenue
Additional information on costs and expenses:
Stock compensation expense	4,218	996	448
Depreciation and amortization expense	8,557	7,831	7,150
Amortization of purchased intangibles	1,138	1,143	2,842
Sales and marketing
Additional information on costs and expenses:
Stock compensation expense	10,010	5,374	2,500
Depreciation and amortization expense	1,642	1,520	1,625
General and administrative
Additional information on costs and expenses:
Stock compensation expense	12,216	4,921	3,691
Depreciation and amortization expense	908	1,083	1,226
Product development
Additional information on costs and expenses:
Stock compensation expense	17,661	3,550	2,305
Depreciation and amortization expense	$ 5,259	$ 3,754	$ 2,357