Segment Information - Summary of Financial Information By Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total revenue	$ 249,838	$ 218,876	$ 222,779
Cost of revenue	62,479	58,205	63,161
Sales and marketing	103,344	90,905	89,529
Amortization of purchased intangibles	1,670	1,840	3,885
Unallocated corporate expenses	106,048	85,752	85,613
Loss from operations	(23,703)	(17,826)	(19,409)
Corporate
Segment Reporting Information [Line Items]
Unallocated corporate expenses	106,048	85,752	85,613
Loss from operations	(106,048)	(85,752)	(85,613)
Business | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	230,285	201,426	206,521
Cost of revenue	58,420	54,600	60,352
Sales and marketing	94,339	82,420	82,063
Amortization of purchased intangibles	1,670	1,840	3,885
Loss from operations	75,856	62,566	60,221
Consumer | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	19,553	17,450	16,258
Cost of revenue	4,059	3,605	2,809
Sales and marketing	9,005	8,485	7,466
Loss from operations	6,489	5,360	5,983
Hosted Services - Business
Segment Reporting Information [Line Items]
Total revenue	197,474	178,686	183,551
Hosted Services - Business | Business | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	197,474	178,686	183,551
Hosted Services - Consumer
Segment Reporting Information [Line Items]
Total revenue	19,553	17,450	16,258
Hosted Services - Consumer | Consumer | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	19,553	17,450	16,258
Professional Services
Segment Reporting Information [Line Items]
Total revenue	32,811	22,740	22,970
Professional Services | Business | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	$ 32,811	$ 22,740	$ 22,970