Segment and Geographic Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment									1
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 109,029	$ 107,758	$ 107,013	$ 99,324	$ 95,862	$ 87,271	$ 82,563	$ 73,955	$ 423,124	$ 339,651	$ 263,568
Property and equipment, net	23,962				27,021				23,962	27,021
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									284,657	228,724	180,834
Property and equipment, net	19,843				22,072				19,843	22,072
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									27,571	30,104	28,938
Property and equipment, net	2,985				3,272				2,985	3,272
All other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									110,896	80,823	$ 53,796
Property and equipment, net	$ 1,134				$ 1,677				1,134	1,677
Subscription Revenue | Sales Revenue, Services, Net | Product Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 339,756	$ 270,093
Percentage of revenue to total									80.30%	79.50%
Professional Services Revenue | Sales Revenue, Services, Net | Product Concentration Risk
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 83,368	$ 69,558
Percentage of revenue to total									19.70%	20.50%