Revenue Recognition (Revenue by Geographic Region) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue		$ 61,660	$ 54,074	$ 119,901	$ 104,993
United States
Disaggregation of Revenue [Line Items]
Revenue		35,572	34,078	69,643	65,763
Other Americas
Disaggregation of Revenue [Line Items]
Revenue	[1]	2,547	1,968	3,806	3,940
Total Americas
Disaggregation of Revenue [Line Items]
Revenue		38,119	36,046	73,449	69,703
EMEA
Disaggregation of Revenue [Line Items]
Revenue	[2],[3]	17,519	13,953	34,438	27,465
APAC
Disaggregation of Revenue [Line Items]
Revenue	[4]	6,022	4,075	12,014	7,825
United Kingdom
Disaggregation of Revenue [Line Items]
Revenue		$ 11,900	$ 9,100	$ 23,500	$ 18,200

[1] Canada, Latin America and South America

[2] Europe, the Middle East and Africa (“EMEA”)

[3] Includes revenues from the United Kingdom of $11.9 million and $9.1 million for the three months ended June 30, 2018 and 2017, respectively, and $23.5 million and $18.2 million six months ended June 30, 2018 and 2017, respectively.

[4] Asia-Pacific (“APAC”)