Geographical Information - Schedule of Revenue and Property and Equipment by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets
Revenue	$ 55,403	$ 50,081	$ 47,727	$ 47,014	$ 44,207	$ 40,982	$ 38,886	$ 38,015	$ 200,225	$ 162,090	$ 128,868
Property and equipment, net	19,888				14,688				19,888	14,688	13,225
United States
Revenues from External Customers and Long-Lived Assets
Revenue									188,303	151,484	120,037
Property and equipment, net	17,949				13,025				17,949	13,025	10,939
International
Revenues from External Customers and Long-Lived Assets
Revenue									11,922	10,606	8,831
Property and equipment, net	$ 1,939				$ 1,663				$ 1,939	$ 1,663	$ 2,286