Revenue Recognition (Revenue by Geographic Region) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue		$ 58,241	$ 50,919
United States [Member]
Disaggregation of Revenue [Line Items]
Revenue		34,071	31,684
Other Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue	[1]	1,259	1,972
Total Americas [Member]
Disaggregation of Revenue [Line Items]
Revenue		35,330	33,656
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenue	[2],[3]	16,919	13,513
APAC [Member]
Disaggregation of Revenue [Line Items]
Revenue	[4]	5,992	3,750
United Kingdom [Member]
Disaggregation of Revenue [Line Items]
Revenue		$ 11,700	$ 9,000

[1] Canada, Latin America and South America

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

[3] Includes revenues from the United Kingdom of $11.7 million and $9.0 million for the three months ended March 31, 2018 and 2017, respectively.

[4] Asia-Pacific (“APAC”)