Segment Information - Financial Information by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total revenue	$ 366,620	$ 291,609	$ 249,838
Cost of revenue	106,268	78,878	62,479
Sales and marketing	149,773	156,814	103,344
Amortization of purchased intangibles	1,639	1,794	1,670
Unallocated corporate expenses	198,391	141,155	106,048
Loss from operations	(89,451)	(87,032)	(23,703)
Corporate
Segment Reporting Information [Line Items]
Unallocated corporate expenses	198,391	141,155	106,048
Loss from operations	(198,391)	(141,155)	(106,048)
Business | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	336,856	267,129	230,285
Cost of revenue	99,394	74,460	58,420
Sales and marketing	128,752	140,880	94,339
Amortization of purchased intangibles	1,639	1,794	1,670
Loss from operations	107,071	49,995	75,856
Consumer | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	29,764	24,480	19,553
Cost of revenue	6,874	4,418	4,059
Sales and marketing	21,021	15,934	9,005
Loss from operations	1,869	4,128	6,489
Hosted Services - Business
Segment Reporting Information [Line Items]
Total revenue	286,588	225,705	197,474
Hosted Services - Business | Business | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	286,588	225,705	197,474
Hosted Services - Consumer
Segment Reporting Information [Line Items]
Total revenue	29,764	24,480	19,553
Hosted Services - Consumer | Consumer | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	29,764	24,480	19,553
Professional Services - Business
Segment Reporting Information [Line Items]
Total revenue	50,268	41,424	32,811
Professional Services - Business | Business | Operating Segments
Segment Reporting Information [Line Items]
Total revenue	$ 50,268	$ 41,424	$ 32,811