Description of Business and Summary of Significant Accounting Policies - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 291,609	$ 249,838	$ 218,876
Hosted Services - Business
Disaggregation of Revenue [Line Items]
Total revenue	225,705	197,474	178,686
Hosted Services - Consumer
Disaggregation of Revenue [Line Items]
Total revenue	24,480	19,553	17,450
Professional Services
Disaggregation of Revenue [Line Items]
Total revenue	$ 41,424	$ 32,811	$ 22,740