Summary of Significant Accounting Policies - Estimated Useful Lives of Property and Equipment - (Details)	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Estimated useful lives of property and equipment	2 years 4 months 24 days
Furniture and fixtures
Property Plant And Equipment [Line Items]
Estimated useful lives of property and equipment	5 years
Hosting equipment
Property Plant And Equipment [Line Items]
Estimated useful lives of property and equipment	3 years
Minimum | Computer equipment and licensed software and patents
Property Plant And Equipment [Line Items]
Estimated useful lives of property and equipment	3 years
Maximum | Computer equipment and licensed software and patents
Property Plant And Equipment [Line Items]
Estimated useful lives of property and equipment	5 years