Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue	$ 249,838	$ 218,876	$ 222,779
Costs and expenses:
Cost of revenue	62,479	58,205	63,161
Sales and marketing	103,344	90,905	89,529
General and administrative	45,873	43,124	43,046
Product development	55,707	40,034	40,198
Restructuring costs	4,468	2,594	2,369
Amortization of purchased intangibles	1,670	1,840	3,885
Total costs and expenses	273,541	236,702	242,188
Loss from operations	(23,703)	(17,826)	(19,409)
Other (expense) income, net	(471)	136	(530)
Loss before provision for income taxes	(24,174)	(17,690)	(19,939)
Provision for income taxes	858	501	5,934
Net loss	$ (25,032)	$ (18,191)	$ (25,873)
Net loss per share of common stock:
Basic (in dollars per share)	$ (0.42)	$ (0.32)	$ (0.46)
Diluted (in dollars per share)	$ (0.42)	$ (0.32)	$ (0.46)
Weighted-average shares used to compute net loss income per share:
Basic (in shares)	59,203,400	56,358,017	56,063,777
Diluted (in shares)	59,203,400	56,358,017	56,063,777
Additional Information on Operating Expenses:
Stock compensation expense	$ 14,841	$ 8,944	$ 9,736
Cost Of Revenue [Member]
Additional Information on Operating Expenses:
Stock compensation expense	996	448	429
Depreciation expense	7,831	7,150	8,234
Amortization of purchased intangibles	1,143	2,842	2,788
Sales and Marketing [Member]
Additional Information on Operating Expenses:
Stock compensation expense	5,374	2,500	2,515
Depreciation expense	1,520	1,625	1,315
General and Administrative [Member]
Additional Information on Operating Expenses:
Stock compensation expense	4,921	3,691	3,304
Depreciation expense	1,083	1,226	1,418
Product Development [Member]
Additional Information on Operating Expenses:
Stock compensation expense	3,550	2,305	3,488
Depreciation expense	$ 3,754	$ 2,357	$ 1,044